rfc8864xml2.original.xml   rfc8864.xml 
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<!ENTITY RFC4960 SYSTEM "http://xml.resource.org/public/rfc/bibxml/refere <front>
nce.RFC.4960.xml"> <title abbrev="SDP-Based Data Channel Negotiation">Negotiation Data Channels
<!ENTITY RFC4582 SYSTEM "http://xml.resource.org/public/rfc/bibxml/refere Using the Session Description Protocol (SDP)</title>
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]> </author>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> <author initials="R." surname="Even" fullname="Roni Even" role="editor">
<?rfc toc="yes" ?> <organization showOnFrontPage="true"/>
<?rfc symrefs="yes" ?> <address>
<?rfc iprnotified="no" ?> <email>ron.even.tlv@gmail.com</email>
<?rfc strict="no" ?> </address>
<?rfc compact="yes" ?> </author>
<?rfc subcompact="no"?> <date month="01" year="2021"/>
<?rfc sortrefs="yes" ?> <abstract pn="section-abstract">
<rfc category="std" docName="draft-ietf-mmusic-data-channel-sdpneg-28" ipr="trus <t indent="0" pn="section-abstract-1"> Data channel setup can be done usi
t200902"> ng either the in-band Data Channel Establishment Protocol (DCEP) or some out-of-
<front> band non-DCEP protocol. This document specifies how the SDP (Session
<title abbrev="SDP-based Data Channel Negotiation">
SDP-based Data Channel Negotiation
</title>
<author initials="K. E." surname="Drage" fullname="Keith Drage">
<organization>Unaffiliated</organization>
<address>
<email>drageke@ntlworld.com</email>
</address>
</author>
<author initials="M. R." surname="Makaraju" fullname="Maridi R. M
akaraju (Raju)">
<organization>Nokia</organization>
<address>
<postal>
<street>2000 Lucent Lane</street>
<city>Naperville</city>
<region>Illinois</region>
<country>US</country>
</postal>
<email> Raju.Makaraju@nokia.com</email>
</address>
</author>
<author fullname="Richard Ejzak" initials="R.P." surname="Ejzak">
<organization>Unaffiliated</organization>
<address>
<email>richard.ejzak@gmail.com</email>
</address>
</author>
<author fullname="Jerome Marcon" initials="J.M." surname="Marcon"
>
<organization>Unaffiliated</organization>
<address>
<email>jeromee.marcon@free.fr</email>
</address>
</author>
<author initials="R. E." surname="Even" fullname="Roni Even" role
="editor">
<organization>Huawei</organization>
<address>
<email>roni.even@huawei.com</email>
</address>
</author>
<date month="May" year="2019"/>
<area>ART</area>
<workgroup>MMUSIC</workgroup>
<abstract>
<t> Data channel setup can be done using either the in-b
and Data Channel Establishment Protocol (DCEP) or using some out-of-band non-DCE
P protocol. This document specifies how the SDP (Session
Description Protocol) offer/answer exchange can be used to achieve Description Protocol) offer/answer exchange can be used to achieve
an out-of-band non-DCEP negotiation for establishing a data channel. an out-of-band non-DCEP negotiation for establishing a data channel.
</t> </t>
</abstract> </abstract>
</front> <boilerplate>
<middle> <section anchor="status-of-memo" numbered="false" removeInRFC="false" toc=
<section title="Introduction" anchor="introduction"> "exclude" pn="section-boilerplate.1">
<t> The concept of establishing a bi-directional <name slugifiedName="name-status-of-this-memo">Status of This Memo</name
>
<t indent="0" pn="section-boilerplate.1-1">
This is an Internet Standards Track document.
</t>
<t indent="0" pn="section-boilerplate.1-2">
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
</t>
<t indent="0" pn="section-boilerplate.1-3">
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
<eref target="https://www.rfc-editor.org/info/rfc8864" brackets="non
e"/>.
</t>
</section>
<section anchor="copyright" numbered="false" removeInRFC="false" toc="excl
ude" pn="section-boilerplate.2">
<name slugifiedName="name-copyright-notice">Copyright Notice</name>
<t indent="0" pn="section-boilerplate.2-1">
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
</t>
<t indent="0" pn="section-boilerplate.2-2">
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<eref target="https://trustee.ietf.org/license-info" brackets="none
"/>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
</t>
</section>
</boilerplate>
<toc>
<section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" p
n="section-toc.1">
<name slugifiedName="name-table-of-contents">Table of Contents</name>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="section-to
c.1-1">
<li pn="section-toc.1-1.1">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.1"><xref der
ivedContent="1" format="counter" sectionFormat="of" target="section-1"/>.  <xref
derivedContent="" format="title" sectionFormat="of" target="name-introduction">
Introduction</xref></t>
</li>
<li pn="section-toc.1-1.2">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.2.1"><xref der
ivedContent="2" format="counter" sectionFormat="of" target="section-2"/>.  <xref
derivedContent="" format="title" sectionFormat="of" target="name-conventions">C
onventions</xref></t>
</li>
<li pn="section-toc.1-1.3">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.3.1"><xref der
ivedContent="3" format="counter" sectionFormat="of" target="section-3"/>.  <xref
derivedContent="" format="title" sectionFormat="of" target="name-terminology">T
erminology</xref></t>
</li>
<li pn="section-toc.1-1.4">
<t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" form
at="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-applicability-statement">Applicabi
lity Statement</xref></t>
</li>
<li pn="section-toc.1-1.5">
<t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" form
at="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-sdp-data-channel-attributes">SDP D
ata Channel Attributes</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.5.2">
<li pn="section-toc.1-1.5.2.1">
<t indent="0" pn="section-toc.1-1.5.2.1.1"><xref derivedContent=
"5.1" format="counter" sectionFormat="of" target="section-5.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-sdp-dcmap-attribute">S
DP DCMAP Attribute</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
ction-toc.1-1.5.2.1.2">
<li pn="section-toc.1-1.5.2.1.2.1">
<t indent="0" pn="section-toc.1-1.5.2.1.2.1.1"><xref derived
Content="5.1.1" format="counter" sectionFormat="of" target="section-5.1.1"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcmap-attr
ibute-syntax">DCMAP Attribute Syntax</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.2">
<t indent="0" pn="section-toc.1-1.5.2.1.2.2.1"><xref derived
Content="5.1.2" format="counter" sectionFormat="of" target="section-5.1.2"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcmap-stre
am-id-parameter">'dcmap-stream-id' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.3">
<t indent="0" pn="section-toc.1-1.5.2.1.2.3.1"><xref derived
Content="5.1.3" format="counter" sectionFormat="of" target="section-5.1.3"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-label-para
meter">'label' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.4">
<t indent="0" pn="section-toc.1-1.5.2.1.2.4.1"><xref derived
Content="5.1.4" format="counter" sectionFormat="of" target="section-5.1.4"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-subprotoco
l-parameter">'subprotocol' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.5">
<t indent="0" pn="section-toc.1-1.5.2.1.2.5.1"><xref derived
Content="5.1.5" format="counter" sectionFormat="of" target="section-5.1.5"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-max-retr-p
arameter">'max-retr' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.6">
<t indent="0" pn="section-toc.1-1.5.2.1.2.6.1"><xref derived
Content="5.1.6" format="counter" sectionFormat="of" target="section-5.1.6"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-max-time-p
arameter">'max-time' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.7">
<t indent="0" pn="section-toc.1-1.5.2.1.2.7.1"><xref derived
Content="5.1.7" format="counter" sectionFormat="of" target="section-5.1.7"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-ordered-pa
rameter">'ordered' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.8">
<t indent="0" pn="section-toc.1-1.5.2.1.2.8.1"><xref derived
Content="5.1.8" format="counter" sectionFormat="of" target="section-5.1.8"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-priority-p
arameter">'priority' Parameter</xref></t>
</li>
<li pn="section-toc.1-1.5.2.1.2.9">
<t indent="0" pn="section-toc.1-1.5.2.1.2.9.1"><xref derived
Content="5.1.9" format="counter" sectionFormat="of" target="section-5.1.9"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcmap-mult
iplexing-category">DCMAP Multiplexing Category</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.5.2.2">
<t indent="0" pn="section-toc.1-1.5.2.2.1"><xref derivedContent=
"5.2" format="counter" sectionFormat="of" target="section-5.2"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-sdp-dcsa-attribute">SD
P DCSA Attribute</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
ction-toc.1-1.5.2.2.2">
<li pn="section-toc.1-1.5.2.2.2.1">
<t indent="0" pn="section-toc.1-1.5.2.2.2.1.1"><xref derived
Content="5.2.1" format="counter" sectionFormat="of" target="section-5.2.1"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcsa-attri
bute-syntax">DCSA Attribute Syntax</xref></t>
</li>
<li pn="section-toc.1-1.5.2.2.2.2">
<t indent="0" pn="section-toc.1-1.5.2.2.2.2.1"><xref derived
Content="5.2.2" format="counter" sectionFormat="of" target="section-5.2.2"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcsa-multi
plexing-category">DCSA Multiplexing Category</xref></t>
</li>
</ul>
</li>
</ul>
</li>
<li pn="section-toc.1-1.6">
<t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" form
at="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-sdp-offer-answer-procedures">SDP O
ffer/Answer Procedures</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.6.2">
<li pn="section-toc.1-1.6.2.1">
<t indent="0" pn="section-toc.1-1.6.2.1.1"><xref derivedContent=
"6.1" format="counter" sectionFormat="of" target="section-6.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-managing-stream-identi
fiers">Managing Stream Identifiers</xref></t>
</li>
<li pn="section-toc.1-1.6.2.2">
<t indent="0" pn="section-toc.1-1.6.2.2.1"><xref derivedContent=
"6.2" format="counter" sectionFormat="of" target="section-6.2"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-negotiating-data-chann
el-pa">Negotiating Data Channel Parameters</xref></t>
</li>
<li pn="section-toc.1-1.6.2.3">
<t indent="0" pn="section-toc.1-1.6.2.3.1"><xref derivedContent=
"6.3" format="counter" sectionFormat="of" target="section-6.3"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-generating-the-initial
-offe">Generating the Initial Offer for a Data Channel</xref></t>
</li>
<li pn="section-toc.1-1.6.2.4">
<t indent="0" pn="section-toc.1-1.6.2.4.1"><xref derivedContent=
"6.4" format="counter" sectionFormat="of" target="section-6.4"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-generating-the-sdp-ans
wer">Generating the SDP Answer</xref></t>
</li>
<li pn="section-toc.1-1.6.2.5">
<t indent="0" pn="section-toc.1-1.6.2.5.1"><xref derivedContent=
"6.5" format="counter" sectionFormat="of" target="section-6.5"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-offerer-processing-of-
the-s">Offerer Processing of the SDP Answer</xref></t>
</li>
<li pn="section-toc.1-1.6.2.6">
<t indent="0" pn="section-toc.1-1.6.2.6.1"><xref derivedContent=
"6.6" format="counter" sectionFormat="of" target="section-6.6"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-modifying-the-session"
>Modifying the Session</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
ction-toc.1-1.6.2.6.2">
<li pn="section-toc.1-1.6.2.6.2.1">
<t indent="0" pn="section-toc.1-1.6.2.6.2.1.1"><xref derived
Content="6.6.1" format="counter" sectionFormat="of" target="section-6.6.1"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-closing-a-
data-channel">Closing a Data Channel</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.6.2.7">
<t indent="0" pn="section-toc.1-1.6.2.7.1"><xref derivedContent=
"6.7" format="counter" sectionFormat="of" target="section-6.7"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-various-sdp-offer-answ
er-co">Various SDP Offer/Answer Considerations</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.7">
<t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="7" form
at="counter" sectionFormat="of" target="section-7"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-examples">Examples</xref></t>
</li>
<li pn="section-toc.1-1.8">
<t indent="0" pn="section-toc.1-1.8.1"><xref derivedContent="8" form
at="counter" sectionFormat="of" target="section-8"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-security-considerations">Security
Considerations</xref></t>
</li>
<li pn="section-toc.1-1.9">
<t indent="0" pn="section-toc.1-1.9.1"><xref derivedContent="9" form
at="counter" sectionFormat="of" target="section-9"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-iana-considerations">IANA Consider
ations</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.9.2">
<li pn="section-toc.1-1.9.2.1">
<t indent="0" pn="section-toc.1-1.9.2.1.1"><xref derivedContent=
"9.1" format="counter" sectionFormat="of" target="section-9.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-subprotocol-identifier
s">Subprotocol Identifiers</xref></t>
</li>
<li pn="section-toc.1-1.9.2.2">
<t indent="0" pn="section-toc.1-1.9.2.2.1"><xref derivedContent=
"9.2" format="counter" sectionFormat="of" target="section-9.2"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-new-sdp-attributes">Ne
w SDP Attributes</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
ction-toc.1-1.9.2.2.2">
<li pn="section-toc.1-1.9.2.2.2.1">
<t indent="0" pn="section-toc.1-1.9.2.2.2.1.1"><xref derived
Content="9.2.1" format="counter" sectionFormat="of" target="section-9.2.1"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcmap">dcm
ap</xref></t>
</li>
<li pn="section-toc.1-1.9.2.2.2.2">
<t indent="0" pn="section-toc.1-1.9.2.2.2.2.1"><xref derived
Content="9.2.2" format="counter" sectionFormat="of" target="section-9.2.2"/>.  <
xref derivedContent="" format="title" sectionFormat="of" target="name-dcsa">dcsa
</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.9.2.3">
<t indent="0" pn="section-toc.1-1.9.2.3.1"><xref derivedContent=
"9.3" format="counter" sectionFormat="of" target="section-9.3"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-registering-attributes
-for-">Registering Attributes for Use with Data Channels</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.10">
<t indent="0" pn="section-toc.1-1.10.1"><xref derivedContent="10" fo
rmat="counter" sectionFormat="of" target="section-10"/>. <xref derivedContent=""
format="title" sectionFormat="of" target="name-references">References</xref></t
>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.10.2">
<li pn="section-toc.1-1.10.2.1">
<t indent="0" pn="section-toc.1-1.10.2.1.1"><xref derivedContent
="10.1" format="counter" sectionFormat="of" target="section-10.1"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-normative-reference
s">Normative References</xref></t>
</li>
<li pn="section-toc.1-1.10.2.2">
<t indent="0" pn="section-toc.1-1.10.2.2.1"><xref derivedContent
="10.2" format="counter" sectionFormat="of" target="section-10.2"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-informative-referen
ces">Informative References</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.11">
<t indent="0" pn="section-toc.1-1.11.1"><xref derivedContent="Append
ix A" format="default" sectionFormat="of" target="section-appendix.a"/>.  <xref
derivedContent="" format="title" sectionFormat="of" target="name-generic-data-ch
annel-negoti">Generic Data Channel Negotiation Aspects when Not Using DCEP</xref
></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.11.2">
<li pn="section-toc.1-1.11.2.1">
<t indent="0" pn="section-toc.1-1.11.2.1.1"><xref derivedContent
="A.1" format="counter" sectionFormat="of" target="section-a.1"/>.  <xref derive
dContent="" format="title" sectionFormat="of" target="name-stream-identifier-num
bering">Stream Identifier Numbering</xref></t>
</li>
<li pn="section-toc.1-1.11.2.2">
<t indent="0" pn="section-toc.1-1.11.2.2.1"><xref derivedContent
="A.2" format="counter" sectionFormat="of" target="section-a.2"/>.  <xref derive
dContent="" format="title" sectionFormat="of" target="name-generic-data-channel-
negotia">Generic Data Channel Negotiation Not Using DCEP</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="se
ction-toc.1-1.11.2.2.2">
<li pn="section-toc.1-1.11.2.2.2.1">
<t indent="0" pn="section-toc.1-1.11.2.2.2.1.1"><xref derive
dContent="A.2.1" format="counter" sectionFormat="of" target="section-a.2.1"/>.  
<xref derivedContent="" format="title" sectionFormat="of" target="name-overview"
>Overview</xref></t>
</li>
<li pn="section-toc.1-1.11.2.2.2.2">
<t indent="0" pn="section-toc.1-1.11.2.2.2.2.1"><xref derive
dContent="A.2.2" format="counter" sectionFormat="of" target="section-a.2.2"/>.  
<xref derivedContent="" format="title" sectionFormat="of" target="name-opening-a
-data-channel">Opening a Data Channel</xref></t>
</li>
<li pn="section-toc.1-1.11.2.2.2.3">
<t indent="0" pn="section-toc.1-1.11.2.2.2.3.1"><xref derive
dContent="A.2.3" format="counter" sectionFormat="of" target="section-a.2.3"/>.  
<xref derivedContent="" format="title" sectionFormat="of" target="name-closing-a
-data-channel-2">Closing a Data Channel</xref></t>
</li>
</ul>
</li>
</ul>
</li>
<li pn="section-toc.1-1.12">
<t indent="0" pn="section-toc.1-1.12.1"><xref derivedContent="" form
at="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="
" format="title" sectionFormat="of" target="name-acknowledgements">Acknowledgeme
nts</xref></t>
</li>
<li pn="section-toc.1-1.13">
<t indent="0" pn="section-toc.1-1.13.1"><xref derivedContent="" form
at="none" sectionFormat="of" target="section-appendix.c"/><xref derivedContent="
" format="title" sectionFormat="of" target="name-contributors">Contributors</xre
f></t>
</li>
<li pn="section-toc.1-1.14">
<t indent="0" pn="section-toc.1-1.14.1"><xref derivedContent="" form
at="none" sectionFormat="of" target="section-appendix.d"/><xref derivedContent="
" format="title" sectionFormat="of" target="name-authors-addresses">Authors' Add
resses</xref></t>
</li>
</ul>
</section>
</toc>
</front>
<middle>
<section anchor="introduction" numbered="true" removeInRFC="false" toc="incl
ude" pn="section-1">
<name slugifiedName="name-introduction">Introduction</name>
<t indent="0" pn="section-1-1"> The concept of establishing a bidirectio
nal
data channel running on top of the Stream Control Transmission data channel running on top of the Stream Control Transmission
Protocol (SCTP) is in Protocol (SCTP) is discussed in
<xref target="I-D.ietf-rtcweb-data-channel"/> allowing applications to use data <xref target="RFC8831" format="default" sectionFormat="of" derivedContent="RFC8
channels. An in-band Data 831"/>, allowing applications to use data channels. An in-band Data
Channel Establishment Protocol (DCEP) is in <xref target="I-D.ietf-rtcweb-dat Channel Establishment Protocol (DCEP) is described in <xref target="RFC8832"
a-protocol"/>, format="default" sectionFormat="of" derivedContent="RFC8832"/>;
however other in-band or out-of-band however, other in-band or out-of-band
protocols may be used for establishing data channels. Each data protocols may be used for establishing data channels. Each data
channel consists of paired SCTP streams sharing the same SCTP Stream channel consists of paired SCTP streams sharing the same SCTP Stream
Identifier. Data channels are created by endpoint applications using Identifier. Data channels are created by endpoint applications using
the WebRTC API (Application Programming Interface), or other protocols (1) the WebRTC API (Application Programming Interface) <xref target="WebRtcAP
like CLUE I" format="default" sectionFormat="of" derivedContent="WebRtcAPI"/> or (2)  othe
<xref target="I-D.ietf-clue-datachannel"/>. The protocols can be signaled r protocols
by the data channel "subprotocol" parameter, conceptually similar to (e.g., Controlling Multiple Streams for Telepresence (CLUE)
the WebSocket <xref target="RFC5234"/> "subprotocol". However, apart from the <xref target="RFC8850" format="default" sectionFormat="of" derivedContent="RFC8
850"/>). The protocols can be signaled
by the data channel 'subprotocol' parameter, conceptually similar to
a WebSocket subprotocol as described in <xref target="RFC6455" format="defaul
t" sectionFormat="of" derivedContent="RFC6455"/>.
However, apart from the
"subprotocol" value transmitted to the peer, an endpoint application can agre e on how to instantiate a given "subprotocol" value transmitted to the peer, an endpoint application can agre e on how to instantiate a given
subprotocol on a data channel, and whether it is signaled in-band subprotocol on a data channel, and whether it is signaled in-band
using DCEP or out-of-band using a non-DCEP protocol (or both). </t> using DCEP or out-of-band using a non-DCEP protocol (or both).</t>
<t>This document defines SDP offer/answer <xref target="R <t indent="0" pn="section-1-2">This document defines Session Description P
FC3264"/> procedures that enable out-of-band negotiation rotocol (SDP) offer/answer
procedures <xref target="RFC3264" format="default" sectionFormat="of" deri
vedContent="RFC3264"/> that enable out-of-band negotiation
for establishing data channels for transport of well-defined subprotocols. for establishing data channels for transport of well-defined subprotocols.
These procedures are based on generic SDP offer/answer negotiation rules for These procedures are based on generic SDP offer/answer negotiation rules for
SCTP SCTP-based media transport as specified in <xref target="RFC8841" format="defaul
based media transport as specified in <xref target="I-D.ietf-mmusic-sctp-sdp" t" sectionFormat="of" derivedContent="RFC8841"/> for
/> for the SDP "m=" line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP.
the SDP "m" line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. </t>
<t indent="0" pn="section-1-3">This document uses MSRP (the Message Sessio
</t> n Relay Protocol) <xref target="RFC4975" format="default" sectionFormat="of" der
<t>This document uses MSRP (Message Session Relay Protoco ivedContent="RFC4975"/>
l) <xref target="RFC4975"/> and BFCP (the Binary Floor Control Protocol) <xref target="RFC8855" format="d
and BFCP (Binary Floor Control Protocol) <xref target="RFC4582"/> in many of efault" sectionFormat="of" derivedContent="RFC8855"/> in several examples. It do
the examples. It does not provide a es not provide a
complete specification of how to negotiate the use of a data channel to trans port complete specification of how to negotiate the use of a data channel to trans port
MSRP. Procedures specific to each MSRP. Procedures specific to each
subprotocol would have to be documented elsewhere. For MSRP they are document ed in <xref target="I-D.ietf-mmusic-msrp-usage-data-channel"/> . The use of MSRP in some examples is only to show how the generic subprotocol would have to be documented elsewhere. For MSRP, they are documen ted in <xref target="RFC8873" format="default" sectionFormat="of" derivedContent ="RFC8873"/>. The use of MSRP in some examples is only to show how the generic
procedures described herein might apply to a specific subprotocol. procedures described herein might apply to a specific subprotocol.
</t> </t>
</section> </section>
<section title="Conventions"> <section numbered="true" removeInRFC="false" toc="include" pn="section-2">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", <name slugifiedName="name-conventions">Conventions</name>
"SHALL NOT", <t indent="0" pn="section-2-1">The key words "<bcp14>MUST</bcp14>", "<bcp1
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED","MAY", and "OPTIONAL 4>MUST NOT</bcp14>",
" in this "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>",
document are to be interpreted as described in BCP14 <xref target="RFC2119"/ "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>",
> "<bcp14>SHOULD NOT</bcp14>",
<xref target="RFC8174"/> when, and only when, the "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
y "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are
appear in all capitals, as shown here. to be interpreted as described in BCP 14 <xref target="RFC2119" format="def
ault" sectionFormat="of" derivedContent="RFC2119"/>
</t> <xref target="RFC8174" format="default" sectionFormat="of" derivedConten
</section> t="RFC8174"/> when, and only when, they appear in all capitals,
<section title="Terminology" anchor="terminology"> as shown here.</t>
<t>This document uses the following terms: </section>
<list style="hanging"> <section anchor="terminology" numbered="true" removeInRFC="false" toc="inclu
<t>Data channel: A WebRTC data channel as de" pn="section-3">
specified in <name slugifiedName="name-terminology">Terminology</name>
<xref target="I-D.ietf-rtcweb-data-channel"/>.</t> <t indent="0" pn="section-3-1">This document uses the following terms:
<t>Data channel stack: An entity which, u </t>
pon application request, <dl newline="false" spacing="normal" indent="3" pn="section-3-2">
runs the data channel protocol to keep track of states, sending and receivi <dt pn="section-3-2.1">Data channel:</dt>
ng <dd pn="section-3-2.2">A WebRTC data channel as specified in
data. If the application is a browser based JavaScript application <xref target="RFC8831" format="default" sectionFormat="of" derivedContent="
RFC8831"/>.</dd>
<dt pn="section-3-2.3">Data channel stack:</dt>
<dd pn="section-3-2.4">An entity that, upon application request,
runs the data channel protocol to keep track of states as well as the
sending and receiving of data. If the application is a browser-based JavaSc
ript application,
then this stack resides in the browser. If the application is a then this stack resides in the browser. If the application is a
native application then this stack resides in the application and is access native application, then this stack resides in the application and is acces
ible sible
via some sort of APIs.</t> via some sort of API or APIs.</dd>
<t>Data channel properties: Fixed propert <dt pn="section-3-2.5">Data channel properties:</dt>
ies assigned to a data <dd pn="section-3-2.6">Fixed properties assigned to a data
channel at the time of its creation. Some of these properties channel at the time of its creation. Some of these properties
determine the way the data channel stack transmits data on this determine the way the data channel stack transmits data on this
channel (e.g., stream identifier, reliability, order of delivery, etc.).</t channel (e.g., stream identifier, reliability, order of delivery).</dd>
> <dt pn="section-3-2.7">Data channel subprotocol:</dt>
<t>Data channel subprotocol: The applicat <dd pn="section-3-2.8">The application protocol that is transported
ion protocol which is transported
over a single data channel. Data channel subprotocol messages are sent as d ata over a single data channel. Data channel subprotocol messages are sent as d ata
channel payload over an established data channel. SDP offer/answer exchange can be used channel payload over an established data channel. An SDP offer/answer excha nge can be used
as specified in this document to negotiate the establishment of data channe ls, as specified in this document to negotiate the establishment of data channe ls,
corresponding data channel properties, associated data channel subprotocols corresponding data channel properties, associated data channel subprotocols
and data , and data
channel subprotocol properties. In this case the data channel subprotocols channel subprotocol properties. In this case, the data channel subprotocols
may be identified may be identified
by the values of the "subprotocol" parameters of the SDP "a=dcmap" attribut by the values of the 'subprotocol' parameters of the SDP "a=dcmap:" attribu
e as te as
described in <xref target="subprotocol-parameter"/>. Within this document t described in <xref target="subprotocol-parameter" format="default" sectionF
he term ormat="of" derivedContent="Section 5.1.4"/>. Within this document, the term
"data channel subprotocol" is often abbreviated as just "subprotocol". "data channel subprotocol" is often abbreviated as just "subprotocol".
</t> </dd>
<t>DCEP: Data Channel Establishment Proto <dt pn="section-3-2.9">DCEP:</dt>
col defined in <dd pn="section-3-2.10">Data Channel Establishment Protocol, as defined
<xref target="I-D.ietf-rtcweb-data-protocol"/>.</t> in
<t>In-band: Transmission through the peer <xref target="RFC8832" format="default" sectionFormat="of" derivedContent="
-to-peer SCTP association.</t> RFC8832"/>.</dd>
<t>Out-of-band: Transmission through the <dt pn="section-3-2.11">In-band:</dt>
application signaling path.</t> <dd pn="section-3-2.12">Transmission through the peer-to-peer SCTP assoc
<t>Peer: From the perspective of one of t iation.</dd>
he agents in a session, its <dt pn="section-3-2.13">Out-of-band:</dt>
<dd pn="section-3-2.14">Transmission through the application signaling p
ath.</dd>
<dt pn="section-3-2.15">Peer:</dt>
<dd pn="section-3-2.16">From the perspective of one of the agents in a s
ession, its
peer is the other agent. Specifically, from the perspective of the peer is the other agent. Specifically, from the perspective of the
SDP offerer, the peer is the SDP answerer. From the perspective of SDP offerer, the peer is the SDP answerer. From the perspective of
the SDP answerer, the peer is the SDP offerer.</t> the SDP answerer, the peer is the SDP offerer.</dd>
<t>SCTP Stream Sequence Number (SSN): the <dt pn="section-3-2.17">SCTP Stream Sequence Number (SSN):</dt>
SCTP stream sequence number as specified <dd pn="section-3-2.18">The SCTP Stream Sequence Number, as specified
in <xref target="RFC4960"/>.</t> in <xref target="RFC4960" format="default" sectionFormat="of" derivedConten
<t>Stream identifier: The identifier of t t="RFC4960"/>.</dd>
he outbound and inbound <dt pn="section-3-2.19">Stream identifier:</dt>
SCTP streams composing a data channel.</t> <dd pn="section-3-2.20">The identifier of the outbound and inbound
</list> SCTP streams composing a data channel.</dd>
</t> </dl>
</section> </section>
<section title=" Applicability Statement" anchor="appl_statement" <section anchor="appl_statement" numbered="true" removeInRFC="false" toc="in
> clude" pn="section-4">
<t> The mechanism in this document only applies to the Se <name slugifiedName="name-applicability-statement">Applicability Statement
ssion Description </name>
Protocol (SDP) <xref target="I-D.ietf-mmusic-rfc4566bis"/> when used together <t indent="0" pn="section-4-1"> The mechanism described in this document o
with the SDP offer/answer nly applies to SDP <xref target="RFC8866" format="default" sectionFormat="of" de
mechanism <xref target="RFC3264"/>. Declarative usage of SDP is out of scope rivedContent="RFC8866"/> when used together with the SDP offer/answer
for this mechanism <xref target="RFC3264" format="default" sectionFormat="of" derivedC
document, and is thus undefined.</t> ontent="RFC3264"/>. Declarative usage of SDP is out of scope for this
</section> document and is thus undefined.</t>
<section title="SDP Data Channel Attributes" anchor="sdp_synt"> </section>
<t>This section defines two new SDP media-level attribute <section anchor="sdp_synt" numbered="true" removeInRFC="false" toc="include"
s that can be used together with the SDP Offer/Answer mechanism to negotiate dat pn="section-5">
a channel-specific and subprotocol-specific parameters without the usage of DCEP <name slugifiedName="name-sdp-data-channel-attributes">SDP Data Channel At
<xref target="I-D.ietf-rtcweb-data-protocol"/>. The first attribute provides fo tributes</name>
r negotiation of <t indent="0" pn="section-5-1">This section defines two new SDP media-leve
channel-specific parameters. The second attribute provides for l attributes that can be
used together with the SDP Offer/Answer mechanism to negotiate
data-channel-specific and subprotocol-specific parameters without the
usage of DCEP <xref target="RFC8832" format="default" sectionFormat="of" d
erivedContent="RFC8832"/>. The first attribute (<xref target="subsec-sdp-attr-fo
r-dc-par-neg" format="default" sectionFormat="of" derivedContent="Section 5.1"/>
) provides for negotiation of
channel-specific parameters. The second attribute (<xref target="prot_att"
format="default" sectionFormat="of" derivedContent="Section 5.2"/>) provides for
negotiation of subprotocol-specific parameters.</t> negotiation of subprotocol-specific parameters.</t>
<t> <aside pn="section-5-2">
Note: Appendix A provides information how data channels work in general and <t indent="0" pn="section-5-2.1">
especially summarizes some key aspects, which should be considered Note: <xref target="generic-out-of-band-aspects" format="default" sectionFormat=
for the negotiation of data channels if DCEP is not used. "of" derivedContent="Appendix A"/> provides information
</t> regarding how data channels work in general. In particular, it
<section title="SDP DCMAP Attribute " anchor="subsec-sdp- summarizes some key aspects that should be considered
attr-for-dc-par-neg"> for the negotiation of data channels if DCEP is not used.</t>
<t>This section defines a new media level attribu </aside>
te "a=dcmap:" that defines the data channel parameters for <section anchor="subsec-sdp-attr-for-dc-par-neg" numbered="true" removeInR
FC="false" toc="include" pn="section-5.1">
<name slugifiedName="name-sdp-dcmap-attribute">SDP DCMAP Attribute</name
>
<t indent="0" pn="section-5.1-1">This section defines a new media-level
attribute, "a=dcmap:", that defines the data channel parameters for
each data channel to be negotiated. </t> each data channel to be negotiated. </t>
<t>The attribute is used to create bi-directional SCTP data channels <t indent="0" pn="section-5.1-2">This attribute is used to create bidire ctional SCTP data channels
having the same set of attributes. The data channel properties having the same set of attributes. The data channel properties
(reliable/partially reliable, ordered/unordered) need to be suitable per the subprotocol transport requirements. (reliable / partially reliable, ordered/unordered) need to be suitable per th e subprotocol transport requirements.
</t> </t>
<section title="DCMAP Attribute Syntax" anchor="d <section anchor="dcmap-attr-definition" numbered="true" removeInRFC="fal
cmap-attr-definition"> se" toc="include" pn="section-5.1.1">
<t>"a=dcmap:" is a media level attribute <name slugifiedName="name-dcmap-attribute-syntax">DCMAP Attribute Synt
having the following ABNF ax</name>
(Augmented Backus-Naur Form, <xref target="RFC5234"/>) syntax. <t indent="0" pn="section-5.1.1-1">"a=dcmap:" is a media-level attribu
te having the following
<figure align="left" title=""> definition and ABNF (Augmented Backus-Naur Form) syntax <xref target="
<artwork align="left"><![ RFC5234" format="default" sectionFormat="of" derivedContent="RFC5234"/>.
CDATA[
Formal Syntax:
Name: dcmap
Value: dcmap-value
Usage Level: media
Charset Dependent: no
Syntax:
</t>
<table anchor="dcmap-attrib" align="center" pn="table-1">
<name slugifiedName="name-adcmap-attribute-definition">"a=dcmap:" At
tribute Definition</name>
<thead>
<tr>
<th colspan="2" align="center" rowspan="1">"a=dcmap:" Attribute<
/th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" colspan="1" rowspan="1">Name</td>
<td align="left" colspan="1" rowspan="1">dcmap</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Value</td>
<td align="left" colspan="1" rowspan="1">dcmap-value</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Usage Level</td>
<td align="left" colspan="1" rowspan="1">media</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Charset Dependent</td>
<td align="left" colspan="1" rowspan="1">No</td>
</tr>
</tbody>
</table>
<t indent="0" pn="section-5.1.1-3">Formal syntax:</t>
<sourcecode name="abnf-1" type="abnf" markers="false" pn="section-5.1.
1-4">
dcmap-value = dcmap-stream-id dcmap-value = dcmap-stream-id
[ SP dcmap-opt *(";" dcmap-opt) ] [ SP dcmap-opt *(";" dcmap-opt) ]
dcmap-opt = ordering-opt / subprotocol-opt / label-opt dcmap-opt = ordering-opt / subprotocol-opt / label-opt
/ maxretr-opt / maxtime-opt / priority-opt / maxretr-opt / maxtime-opt / priority-opt
; maxretr-opt and maxtime-opt are mutually exclusive ; maxretr-opt and maxtime-opt are
; ; mutually exclusive
dcmap-stream-id = 1*5DIGIT dcmap-stream-id = 1*5DIGIT
ordering-opt = "ordered=" ordering-value ordering-opt = "ordered=" ordering-value
ordering-value = "true" / "false" ordering-value = "true" / "false"
subprotocol-opt = "subprotocol=" quoted-string subprotocol-opt = "subprotocol=" quoted-string
label-opt = "label=" quoted-string label-opt = "label=" quoted-string
maxretr-opt = "max-retr=" maxretr-value maxretr-opt = "max-retr=" maxretr-value
maxretr-value = "0" / integer maxretr-value = "0" / integer
; number of retransmissions, ; number of retransmissions,
; less than 2^32, ; less than 2^32,
; derived from 'Reliability Parameter' of ; derived from 'Reliability Parameter' [RFC8832]
; [I-D.ietf-rtcweb-data-protocol]
maxtime-opt = "max-time=" maxtime-value maxtime-opt = "max-time=" maxtime-value
maxtime-value = "0" / integer maxtime-value = "0" / integer
; milliseconds, ; milliseconds,
; less than 2^32, ; less than 2^32,
; derived from 'Reliability Parameter' of ; derived from 'Reliability Parameter' [RFC8832]
; [I-D.ietf-rtcweb-data-protocol]
priority-opt = "priority=" priority-value priority-opt = "priority=" priority-value
priority-value = "0" / integer priority-value = "0" / integer
; unsigned integer value indicating the priority of ; unsigned integer value indicating the priority of
; the data channel, ; the data channel,
; less than 2^16, ; less than 2^16,
; derived from 'Priority' of ; derived from 'Priority' [RFC8832]
; [I-D.ietf-rtcweb-data-protocol]
quoted-string = DQUOTE *(quoted-char / escaped-char) DQUOTE quoted-string = DQUOTE *(quoted-char / escaped-char) DQUOTE
quoted-char = SP / quoted-visible quoted-char = SP / quoted-visible
quoted-visible = %x21 / %x23-24 / %x26-7E ; VCHAR without " or % quoted-visible = %x21 / %x23-24 / %x26-7E ; VCHAR without " or %
escaped-char = "%" HEXDIG HEXDIG escaped-char = "%" HEXDIG HEXDIG
DQUOTE = <from-RFC5234> DQUOTE = &lt;from RFC 5234&gt;
integer = <from-RFC4566> integer = &lt;from RFC 8866&gt;</sourcecode>
<t indent="0" pn="section-5.1.1-5">Examples:</t>
Examples: <sourcecode name="sdp-1" type="sdp" markers="false" pn="section-5.1.1-
6">
a=dcmap:0 a=dcmap:0
a=dcmap:1 subprotocol="bfcp";max-time=60000;priority=512 a=dcmap:1 subprotocol="bfcp";max-time=60000;priority=512
a=dcmap:2 subprotocol="msrp";ordered=true;label="msrp" a=dcmap:2 subprotocol="msrp";ordered=true;label="msrp"
a=dcmap:3 label="Label 1";ordered=false;max-retr=5;priority=128 a=dcmap:3 label="Label 1";ordered=false;max-retr=5;priority=128
a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000 a=dcmap:4 label="foo%09bar";ordered=true;max-time=15000</sourcecode>
]]></artwork> <aside pn="section-5.1.1-7">
</figure> <t indent="0" pn="section-5.1.1-7.1">Note: The last example (a=dcmap
</t> :4) shows a 'label' parameter value
<t> that contains one nonprintable 'escaped-char' character
<list style="hanging">
<t>Note: The last example
(a=dcmap:4) shows a 'label' parameter value
which contains one non-printable 'escaped-char' character
(the tabulator character).</t> (the tabulator character).</t>
</list> </aside>
</t> <t indent="0" pn="section-5.1.1-8">Within an "a=dcmap:" attribute line
<t>Within an 'a=dcmap:' attribute line's 's 'dcmap-opt' value, only one
'dcmap-opt' value only one
'maxretr-opt' parameter or one 'maxtime-opt' parameter may be present. 'maxretr-opt' parameter or one 'maxtime-opt' parameter may be present.
Both MUST NOT be present.</t> Both parameters <bcp14>MUST NOT</bcp14> be present.</t>
</section> </section>
<section title="Dcmap-stream-id Parameter" anchor <section anchor="dcmap-stream-id-param-definition" numbered="true" remov
="dcmap-stream-id-param-definition"> eInRFC="false" toc="include" pn="section-5.1.2">
<t>The 'dcmap-stream-id' parameter indica <name slugifiedName="name-dcmap-stream-id-parameter">'dcmap-stream-id'
tes the SCTP stream identifier Parameter</name>
<t indent="0" pn="section-5.1.2-1">The 'dcmap-stream-id' parameter ind
icates the SCTP stream identifier
within the SCTP association used to form the data channel.</t> within the SCTP association used to form the data channel.</t>
</section> </section>
<section title="Label Parameter"> <section numbered="true" removeInRFC="false" toc="include" pn="section-5
<t>The 'label' parameter indicates the na .1.3">
me of the <name slugifiedName="name-label-parameter">'label' Parameter</name>
<t indent="0" pn="section-5.1.3-1">The 'label' parameter indicates the
name of the
channel. It represents a label that can be used to distinguish, channel. It represents a label that can be used to distinguish,
in the context of the WebRTC API <xref target="WebRtcAPI"/>, in the context of the WebRTC API <xref target="WebRtcAPI" format="default " sectionFormat="of" derivedContent="WebRtcAPI"/>,
an RTCDataChannel object from other RTCDataChannel objects. an RTCDataChannel object from other RTCDataChannel objects.
This parameter maps to the 'Label' parameter defined in This parameter maps to the 'Label' parameter defined in
<xref target="I-D.ietf-rtcweb-data-protocol"/>. <xref target="RFC8832" format="default" sectionFormat="of" derivedContent ="RFC8832"/>.
The 'label' parameter is optional. If it is not The 'label' parameter is optional. If it is not
present, then its value defaults to the empty string. present, then its value defaults to the empty string.
</t> </t>
<t>In order to communicate with WEbRTC AP <t indent="0" pn="section-5.1.3-2">In order to communicate with the We
I the label attribute should: bRTC API, the 'label' parameter
<list style="symbols"> should
<t>Serialize the WebRTC l </t>
abel as a UTF-8 string <xref target="RFC3629"/>.</t> <ul spacing="normal" bare="false" empty="false" indent="3" pn="section
<t>Treat the UTF-8 serial -5.1.3-3">
ization as a series of bytes</t> <li pn="section-5.1.3-3.1">Serialize the WebRTC label as a UTF-8 str
<t>For each byte in the s ing <xref target="RFC3629" format="default" sectionFormat="of" derivedContent="R
erialization: FC3629"/>.</li>
<li pn="section-5.1.3-3.2">Treat the UTF-8 serialization as a series
<list style="symb of bytes.</li>
ols"> <li pn="section-5.1.3-3.3">
<t>If the <t indent="0" pn="section-5.1.3-3.3.1">For each byte in the serial
byte can be expressed as a `quoted-char`, do so</t> ization,
<t>Otherw </t>
ise, express the byte as an `escaped-char`.</t> <ul spacing="normal" bare="false" empty="false" indent="3" pn="sec
</list> tion-5.1.3-3.3.2">
</t> <li pn="section-5.1.3-3.3.2.1">If the byte can be expressed as a
</list> 'quoted-char', do so.</li>
</t> <li pn="section-5.1.3-3.3.2.2">Otherwise, express the byte as an
<t>Note: The empty string MAY also be exp 'escaped-char'.</li>
licitly used as a 'label' value, </ul>
</li>
</ul>
<aside pn="section-5.1.3-4">
<t indent="0" pn="section-5.1.3-4.1">Note: The empty string can also
be explicitly used as a 'label' value,
such that 'label=""' is equivalent to the 'label' parameter not being such that 'label=""' is equivalent to the 'label' parameter not being
present at all. present at all.
<xref target="I-D.ietf-rtcweb-data-protocol"/> allows the DATA_CHANNEL_OP EN <xref target="RFC8832" format="default" sectionFormat="of" derivedContent ="RFC8832"/> allows the DATA_CHANNEL_OPEN
message's 'Label' value to be an empty string.</t> message's 'Label' value to be an empty string.</t>
</section> </aside>
<section title="Subprotocol Parameter" anchor="su </section>
bprotocol-parameter"> <section anchor="subprotocol-parameter" numbered="true" removeInRFC="fal
<t>The 'subprotocol' parameter indicates se" toc="include" pn="section-5.1.4">
which protocol the <name slugifiedName="name-subprotocol-parameter">'subprotocol' Paramet
er</name>
<t indent="0" pn="section-5.1.4-1">The 'subprotocol' parameter indicat
es which protocol the
client expects to exchange via the channel. client expects to exchange via the channel.
This parameter maps to the 'Protocol' parameter defined in This parameter maps to the 'Protocol' parameter defined in
<xref target="I-D.ietf-rtcweb-data-protocol"/>. <xref target="RFC8832" format="default" sectionFormat="of" derivedContent
<xref target="IANA_subproto_ids"/> specifies how new subprotocol paramete ="RFC8832"/>.
r <xref target="IANA_subproto_ids" format="default" sectionFormat="of" deri
values are registered. vedContent="Section 9.1"/> specifies how values for new subprotocol parameters a
re registered.
'subprotocol' is an optional parameter. 'subprotocol' is an optional parameter.
If the 'subprotocol' parameter is not present, then its value If the 'subprotocol' parameter is not present, then its value
defaults to an empty string.</t> defaults to an empty string.</t>
<t> Note: The empty string MAY also be ex <aside pn="section-5.1.4-2">
plicitly used as 'subprotocol' value, <t indent="0" pn="section-5.1.4-2.1"> Note: The empty string can als
o be
explicitly used as a 'subprotocol' value,
such that 'subprotocol=""' is equivalent to the 'subprotocol' parameter n ot being such that 'subprotocol=""' is equivalent to the 'subprotocol' parameter n ot being
present at all. <xref target="I-D.ietf-rtcweb-data-protocol"/> allows the present at all. <xref target="RFC8832" format="default" sectionFormat="of
DATA_CHANNEL_OPEN message's 'Subprotocol' value to be an empty string. " derivedContent="RFC8832"/> allows the
</t> DATA_CHANNEL_OPEN message's 'Protocol' value to be an empty string.
</section> </t>
<section title="Max-retr Parameter" anchor="max-r </aside>
etr-param-definition"> </section>
<t>This parameter indicates that the data <section anchor="max-retr-param-definition" numbered="true" removeInRFC=
channel is partially reliable. "false" toc="include" pn="section-5.1.5">
<name slugifiedName="name-max-retr-parameter">'max-retr' Parameter</na
me>
<t indent="0" pn="section-5.1.5-1">This parameter indicates that the d
ata channel is partially reliable.
The 'max-retr' parameter indicates the maximal number of times a user mes sage will The 'max-retr' parameter indicates the maximal number of times a user mes sage will
be retransmitted. The max-retr parameter is optional. If be retransmitted. The 'max-retr' parameter is optional. If
the max-retr parameter and the max-time parameter are not present, then r the 'max-retr' parameter and the 'max-time' parameter are not present, th
eliable en reliable
transmission is performed as specified in <xref target="RFC4960"/>. transmission is performed as specified in <xref target="RFC4960" format="
default" sectionFormat="of" derivedContent="RFC4960"/>.
This parameter maps to the 'Number of RTX' parameter This parameter maps to the 'Number of RTX' parameter
defined in <xref target="I-D.ietf-rtcweb-data-protocol"/>.</t> defined in <xref target="RFC8832" format="default" sectionFormat="of" der
</section> ivedContent="RFC8832"/>.</t>
<section title="Max-time Parameter"> </section>
<t> This parameter indicates that the dat <section numbered="true" removeInRFC="false" toc="include" pn="section-5
a channel is partially reliable. .1.6">
<name slugifiedName="name-max-time-parameter">'max-time' Parameter</na
me>
<t indent="0" pn="section-5.1.6-1"> This parameter indicates that the
data channel is partially reliable.
A user message will no longer be transmitted or retransmitted after A user message will no longer be transmitted or retransmitted after
a specified life-time given in milliseconds in the 'max-time' a specified lifetime, given in milliseconds, in the 'max-time'
parameter. The life-time starts when providing the user message to the pr parameter. The lifetime starts when providing the user message to the pro
otocol stack. tocol stack.
The max-time parameter is optional. If the max-retr parameter and the max-time The 'max-time' parameter is optional. If the 'max-retr' parameter and the 'max-
parameter are not present, then reliable time' parameter are not present, then reliable
transmission is performed as specified in <xref target="RFC4960"/>. transmission is performed as specified in <xref target="RFC4960" format="
default" sectionFormat="of" derivedContent="RFC4960"/>.
This parameter maps to the 'Lifetime in ms' parameter This parameter maps to the 'Lifetime in ms' parameter
defined in <xref target="I-D.ietf-rtcweb-data-protocol"/>.</t> defined in <xref target="RFC8832" format="default" sectionFormat="of" der
</section> ivedContent="RFC8832"/>.</t>
<section title="Ordered Parameter" anchor="ordere </section>
d-param-description"> <section anchor="ordered-param-description" numbered="true" removeInRFC=
<t>The 'ordered' parameter with value "tr "false" toc="include" pn="section-5.1.7">
ue" indicates that the receiver will <name slugifiedName="name-ordered-parameter">'ordered' Parameter</name
>
<t indent="0" pn="section-5.1.7-1">The 'ordered' parameter with value
"true" indicates that the receiver will
dispatch DATA chunks in the data channel to the upper layer dispatch DATA chunks in the data channel to the upper layer
while preserving the order. The ordered parameter is optional and while preserving the order. The 'ordered' parameter is optional and
takes two values: "true" for ordered and "false" for unordered delivery takes two values -- "true" for ordered delivery and "false" for unordered
delivery --
with "true" as the default value. with "true" as the default value.
Any other value is ignored and default "ordered=true" is assumed. Any other value is ignored, and the default "ordered=true" is assumed.
In the absence of this parameter "ordered=true" is assumed. In the absence of this parameter, "ordered=true" is assumed.
This parameter maps to This parameter maps to
the ordered or unordered data channel types as defined in the ordered or unordered data channel types as defined in
<xref target="I-D.ietf-rtcweb-data-protocol"/>.</t> <xref target="RFC8832" format="default" sectionFormat="of" derivedContent
</section> ="RFC8832"/>.</t>
<section title="Priority Parameter" anchor="prior </section>
ity-param-description"> <section anchor="priority-param-description" numbered="true" removeInRFC
<t>The 'priority' parameter indicates the ="false" toc="include" pn="section-5.1.8">
data channel's priority <name slugifiedName="name-priority-parameter">'priority' Parameter</na
me>
<t indent="0" pn="section-5.1.8-1">The 'priority' parameter indicates
the data channel's priority
relative to the priorities of other data channels, which may relative to the priorities of other data channels, which may
additionally exist over the same SCTP association. additionally exist over the same SCTP association.
The 'priority' parameter maps to the 'Priority' parameter defined in The 'priority' parameter maps to the 'Priority' parameter defined in
<xref target="I-D.ietf-rtcweb-data-protocol"/>. <xref target="RFC8832" format="default" sectionFormat="of" derivedContent ="RFC8832"/>.
The 'priority' parameter is optional. The 'priority' parameter is optional.
In the absence of this parameter "priority=256" is assumed. In the absence of this parameter, "priority=256" is assumed.
</t> </t>
</section> </section>
<section title="DCMAP Multiplexing Category" anch <section anchor="dcmap-mux-category" numbered="true" removeInRFC="false"
or="dcmap-mux-category"> toc="include" pn="section-5.1.9">
<t>The multiplexing category <xref target <name slugifiedName="name-dcmap-multiplexing-category">DCMAP Multiplex
="I-D.ietf-mmusic-sdp-mux-attributes"/> of the "a=dcmap:" attribute is SPECIAL. ing Category</name>
</t> <t indent="0" pn="section-5.1.9-1">The multiplexing category <xref tar
<t>As the usage of multiple SCTP associat get="RFC8859" format="default" sectionFormat="of" derivedContent="RFC8859"/> of
ions on top of a single DTLS the "a=dcmap:" attribute is SPECIAL.
association is outside the scope of <xref target="I-D.ietf-mmusic-sctp-sd </t>
p"/>, <t indent="0" pn="section-5.1.9-2">As the usage of multiple SCTP assoc
iations on top of a single DTLS
association is outside the scope of <xref target="RFC8841" format="defaul
t" sectionFormat="of" derivedContent="RFC8841"/>,
no "a=dcmap:" attribute multiplexing rules are specified for the UDP/DTLS /SCTP and no "a=dcmap:" attribute multiplexing rules are specified for the UDP/DTLS /SCTP and
TCP/DTLS/SCTP proto values. TCP/DTLS/SCTP proto values.
If future extensions of <xref target="I-D.ietf-mmusic-sctp-sdp"/> define how to If future extensions of <xref target="RFC8841" format="default" sectionFo rmat="of" derivedContent="RFC8841"/> define how to
negotiate multiplexing of multiple SCTP associations on top of a single D TLS negotiate multiplexing of multiple SCTP associations on top of a single D TLS
association, or how to add multiple SCTP associations to one BUNDLE group , then association or how to add multiple SCTP associations to one BUNDLE group, then
multiplexing rules for the "a=dcmap:" attribute need to be multiplexing rules for the "a=dcmap:" attribute need to be
defined as well, for instance in an extension of this SDP offer/answer ba defined as well -- for instance, in an extension of this specification.
sed data channel </t>
negotiation specification. </section>
</t> </section>
</section> <section anchor="prot_att" numbered="true" removeInRFC="false" toc="includ
</section> e" pn="section-5.2">
<!-- subsec-sdp-attr-for-dc-par-neg --> <name slugifiedName="name-sdp-dcsa-attribute">SDP DCSA Attribute</name>
<section title="SDP DCSA Attribute" anchor="prot_att"> <t indent="0" pn="section-5.2-1">In the SDP media description, each data
<t>In the SDP media description, each data channe channel declaration
l declaration MAY also be followed <bcp14>MAY</bcp14> also be followed by other SDP attributes, which
by other media level SDP attributes, which are either specifically defined apply to the corresponding data channel and its subprotocol. Each of
for or these attributes is represented by one new "a=dcsa:" attribute line
applied to the subprotocol in use. that references another SDP attribute defined for use with this data
Each of these attributes is represented by one new attribute line, and channel's subprotocol. Instructions for registering attributes for use
it includes the contents of a media-level SDP attribute already with a data channel are given in <xref target="IANA-reg-data-channel-att
defined for use with this (sub)protocol in another IETF document. ribs" format="default" sectionFormat="of" derivedContent="Section 9.3"/>.</t>
Subprotocol specific attributes MAY also be defined for exclusive <t indent="0" pn="section-5.2-2">Each SDP attribute that is related to t
use with data channel transport, but MUST use the same syntax he subprotocol and that would normally
described here for other subprotocol related attributes.</t> be used to negotiate the subprotocol using the SDP offer/answer mechanism
<t>Each SDP attribute, related to the subprotocol is replaced with
, that would normally an attribute of the form "a=dcsa:stream-id original‑attribute",
be used to negotiate the subprotocol using SDP offer/answer is replaced wi where "dcsa" stands for "data channel subprotocol attribute",
th "stream-id" is the SCTP stream identifier assigned to this subprotocol
an attribute of the form "a=dcsa:stream-id original-attribute", instance, and "original-attribute" represents the contents of the
where dcsa stands for "data channel subprotocol attribute", subprotocol-related attribute to be included.</t>
stream-id is the SCTP stream identifier assigned to this subprotocol <t indent="0" pn="section-5.2-3">The same syntax applies to any other SD
instance, and original-attribute represents the contents of the P attribute required for
subprotocol related attribute to be included.</t>
<t>The same syntax applies to any other SDP attri
bute required for
negotiation of this instance of the subprotocol.</t> negotiation of this instance of the subprotocol.</t>
<t>The detailed offer/answer procedures for the d <t indent="0" pn="section-5.2-4">The detailed offer/answer procedures fo
csa attribute are dependent on the associated sub-protocol. If no offer/answer p r the dcsa attribute are
rocedures exist for the sub-protocol when used outside of the dcsa attribute, no dependent on the associated subprotocol. If no offer/answer
specification is needed for use with dcsa. The IANA registration procedures for procedures exist for the subprotocol when used outside of the dcsa
the WebSocket Subprotocol Name Registry (<xref target="IANA_subproto_ids"/>) do attribute, no specification is needed for use with dcsa. The IANA
not strictly require a specification of the offer/answer procedures for the sub (Internet Assigned Numbers Authority) registration procedures for the "W
-protocol when used with dcsa. If the sub-protocol has defined offer/answer proc ebSocket Subprotocol Name Registry" (<xref target="IANA_subproto_ids" format="de
edures when used outside of dcsa, such a specification is encouraged to ensure i fault" sectionFormat="of" derivedContent="Section 9.1"/>) do not strictly requir
nteroperability. If the sub-protocol has defined offer/answer procedures when us e a specification of the offer/answer procedures for the subprotocol when used w
ed outside of dcsa, but no specification exists for the offer/answer procedures ith dcsa. If the subprotocol has defined offer/answer procedures when used outsi
for the sub-protocol when used with dcsa, implementations SHOULD assume the use de of dcsa, such a specification is encouraged to ensure interoperability. If th
of the default values for all otherwise-negotiable and applicable sub-protocol p e subprotocol has defined offer/answer procedures when used outside of dcsa but
arameters. no specification exists for the offer/answer procedures for the subprotocol when
used with dcsa, implementations <bcp14>SHOULD</bcp14> assume the use of the def
ault values for all otherwise-negotiable and applicable subprotocol parameters.
</t> </t>
<section title="DCSA Syntax" anchor="dcsa-attribu <section anchor="dcsa-attribute" numbered="true" removeInRFC="false" toc
te"> ="include" pn="section-5.2.1">
<t> <name slugifiedName="name-dcsa-attribute-syntax">DCSA Attribute Syntax
<figure align="left" title=""> </name>
<artwork align="left"><![ <t indent="0" pn="section-5.2.1-1">"a=dcsa:" is a media-level attribut
CDATA[ e having the following definition and
Formal Syntax: ABNF (Augmented Backus-Naur Form) syntax <xref target="RFC5234" format="default"
sectionFormat="of" derivedContent="RFC5234"/>.
Name: dcsa </t>
<table anchor="dcsa-attrib" align="center" pn="table-2">
Value: dcsa-value <name slugifiedName="name-adcsa-attribute-definition">"a=dcsa:" Attr
ibute Definition</name>
Usage Level: media <thead>
<tr>
Charset Dependent: no <th colspan="2" align="center" rowspan="1">"a=dcsa:" Attribute</
th>
Syntax: </tr>
</thead>
<tbody>
<tr>
<td align="left" colspan="1" rowspan="1">Name</td>
<td align="left" colspan="1" rowspan="1">dcsa</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Value</td>
<td align="left" colspan="1" rowspan="1">dcsa-value</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Usage Level</td>
<td align="left" colspan="1" rowspan="1">media</td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">Charset Dependent</td>
<td align="left" colspan="1" rowspan="1">No</td>
</tr>
</tbody>
</table>
<t indent="0" pn="section-5.2.1-3">Formal syntax:</t>
<sourcecode name="abnf-2" type="abnf" markers="false" pn="section-5.2.
1-4">
dcsa-value = stream-id SP attribute dcsa-value = stream-id SP attribute
stream-id = 1*5DIGIT stream-id = 1*5DIGIT
attribute = <from-RFC4566> attribute = &lt;from RFC 8866&gt;</sourcecode>
<t indent="0" pn="section-5.2.1-5">Example:</t>
Example: <sourcecode name="sdp-2" type="sdp" markers="false" pn="section-5.2.1-
6">
a=dcmap:2 subprotocol="msrp";ordered=true;label="msrp" a=dcmap:2 subprotocol="msrp";ordered=true;label="msrp"
a=dcsa:2 accept-types:text/plain a=dcsa:2 accept-types:text/plain</sourcecode>
]]></artwork> <t indent="0" pn="section-5.2.1-7">The reference to <xref target="RFC8
</figure> 866" format="default" sectionFormat="of" derivedContent="RFC8866"/> defines wher
</t> e the
<t>Note that the reference to <xref targe
t="I-D.ietf-mmusic-rfc4566bis"/> defines where the
attribute definition can be found; attribute definition can be found;
it does not provide any limitation on support of attributes it does not provide any limitations on support of attributes
defined in other documents in accordance with this attribute defined in other documents in accordance with this attribute
definition. Note however that not all SDP attributes are suitable definition. However, not all SDP attributes are suitable
as a "a=dcsa:" parameter. IANA SDP parameters contains as an "a=dcsa:" parameter. The registry of IANA SDP parameters contains
the lists of IANA (Internet Assigned Numbers Authority) the lists of IANA-registered session-level and media-level or
registered session and media level or media-level-only SDP attributes.
media level only SDP attributes.</t> </t>
<t>Thus in the example above, the origina <t indent="0" pn="section-5.2.1-8">Thus, in the example above, the ori
l attribute line ginal attribute line
"a=accept-types:text/plain" is represented by the attribute line "a=accept‑types:text/plain" is represented by the attribute line
"a=dcsa:2 accept-types:text/plain", which specifies that this "a=dcsa:2 accept-types:text/plain", which specifies that this
instance of the MSRP subprotocol being transported on the SCTP association using instance of the MSRP subprotocol being transported on the SCTP association using
the data channel with stream id 2 accepts the data channel with stream id 2 accepts
plain text files.</t> plaintext files.</t>
<t>As opposed to the data channel "a=dcma <t indent="0" pn="section-5.2.1-9">As opposed to the data channel "a=d
p:" attribute parameters, cmap:" attribute parameters,
these parameters these parameters
are subject to offer/answer negotiation following the procedures are subject to offer/answer negotiation, following the procedures
defined in the subprotocol specific documents.</t> defined in the subprotocol-specific documents.</t>
<t>It is assumed that in general the usag <t indent="0" pn="section-5.2.1-10">It is assumed that in general the
es of subprotocol related media usages of subprotocol-related
level attributes are independent from the subprotocol's transport protocol media-level attributes are independent from the subprotocol's transport pr
. otocol.
Such transport protocol independent subprotocol related attributes are Such transport-protocol-independent subprotocol-related attributes are
used in the same way as defined in the original subprotocol specification, used in the same way as defined in the original subprotocol specification,
also if the subprotocol is transported over a data channel and if the also if the subprotocol is transported over a data channel and if the
attribute is correspondingly embedded in a "a=dcsa" attribute. attribute is correspondingly embedded in an "a=dcsa:" attribute.
</t> </t>
<t>There may be cases, where the usage of <t indent="0" pn="section-5.2.1-11">There may be cases where the usage
a subprotocol related media level of a subprotocol-related
media-level
attribute depends on the subprotocol's transport protocol. attribute depends on the subprotocol's transport protocol.
In such cases the subprotocol related usage of the attribute is expected t In such cases, the subprotocol-related usage of the attribute is expected
o be to be
described for the data channel transport. A data channel specific usage of described for the data channel transport. A data-channel-specific usage of
a a
subprotocol attribute is expected to be specified in the same document tha t subprotocol attribute is expected to be specified in the same document tha t
registers the subprotocol's identifier for data channel usage as described in registers the subprotocol's identifier for data channel usage as described in
<xref target="IANA_subproto_ids"/>. <xref target="IANA_subproto_ids" format="default" sectionFormat="of" deriv
</t> edContent="Section 9.1"/>.
<t>SDP attributes that are only defined f </t>
or use at the </section>
dcsa usage level, SHALL use the dcsa usage level when registering the <section anchor="dcsa-mux-category" numbered="true" removeInRFC="false"
attribute. If existing media attributes are used in a datachannel toc="include" pn="section-5.2.2">
subprotocol specific way, then a new dcsa usage level <name slugifiedName="name-dcsa-multiplexing-category">DCSA Multiplexin
MUST be defined for the existing media attribute. Where the SDP g Category</name>
attribute is applicable to a particular subprotocol/s this SHALL also <t indent="0" pn="section-5.2.2-1">The multiplexing category of the "a
be registered by indicating the applicable subprotocol identifiers =dcsa:" attribute is SPECIAL.
(see /<xref target="I-D.ietf-mmusic-rfc4566bis"/> section-8.5) along with the </t>
dcsa usage level. <t indent="0" pn="section-5.2.2-2">As the usage of multiple SCTP assoc
iations on top of a single DTLS
</t> association is outside the scope of <xref target="RFC8841" format="defaul
</section> t" sectionFormat="of" derivedContent="RFC8841"/>,
<section title="DCSA Multiplexing Category" ancho
r="dcsa-mux-category">
<t>The multiplexing category of the "a=dc
sa:" attribute is SPECIAL.
</t>
<t>As the usage of multiple SCTP associat
ions on top of a single DTLS
association is outside the scope of <xref target="I-D.ietf-mmusic-sctp-sd
p"/>,
no "a=dcsa:" attribute multiplexing rules are specified for the UDP/DTLS/ SCTP and no "a=dcsa:" attribute multiplexing rules are specified for the UDP/DTLS/ SCTP and
TCP/DTLS/SCTP proto values. TCP⁠/DTLS⁠/SCTP proto values.
If future extensions of <xref target="I-D.ietf-mmusic-sctp-sdp"/> define If future extensions of <xref target="RFC8841" format="default" sectionFo
how to rmat="of" derivedContent="RFC8841"/> define how to
negotiate multiplexing of multiple SCTP associations on top of a single D TLS negotiate multiplexing of multiple SCTP associations on top of a single D TLS
association, or how to add multiple SCTP associations to one BUNDLE group , then association or how to add multiple SCTP associations to one BUNDLE group, then
multiplexing rules for the "a=dcsa:" attribute need to be multiplexing rules for the "a=dcsa:" attribute need to be
defined as well, for instance in an extension of this SDP based data chan defined as well -- for instance, in an extension of this specification.
nel </t>
negotiation specification. </section>
</t> </section>
</section> </section>
</section> <section anchor="section_procedures" numbered="true" removeInRFC="false" toc
<!-- prot_att --> ="include" pn="section-6">
</section> <name slugifiedName="name-sdp-offer-answer-procedures">SDP Offer/Answer Pr
<!-- sdp_sync --> ocedures</name>
<section title="SDP Offer/Answer Procedures" anchor="section_proc <t indent="0" pn="section-6-1">This section defines how data channels can
edures"> be negotiated using the SDP
<t>This section defines how data channels can be negotiat
ed using the SDP
offer/answer mechanism. A given media description can describe multiple offer/answer mechanism. A given media description can describe multiple
data channels (each represented by a separate SDP dcmap attribute) that data channels (each represented by a separate SDP dcmap attribute) that
can be created, modified and closed using different offer/answer exchange s. can be created, modified, and closed using different offer/answer exchang es.
The procedures in this section apply for a given data channel. The procedures in this section apply for a given data channel.
</t> </t>
<t>The generic offer/answer procedures for negotiating th <t indent="0" pn="section-6-2">The generic offer/answer procedures for neg
e SCTP association used to realize data channels are defined in <xref target="I- otiating the SCTP association used to realize data channels are defined in <xref
D.ietf-mmusic-sctp-sdp"/>. This section only defines the data channel specific p target="RFC8841" format="default" sectionFormat="of" derivedContent="RFC8841"/>
rocedures.</t> . This section only defines the data-channel-specific procedures.</t>
<t> “Initial offer” refers to the offer in which a data c <t indent="0" pn="section-6-3"> "Initial offer" refers to the offer in whi
hannel is opened. It can be the initial offer, or a subsequent offer, of the ass ch a data channel is
ociated SDP session.</t> opened. It can be either the initial offer or a subsequent offer of the as
<t>The detailed offer/answer procedures for the dcsa attr sociated SDP session.</t>
ibute are dependent on the associated sub-protocol see <xref target="prot_att"/> <t indent="0" pn="section-6-4">The detailed offer/answer procedures for th
. e dcsa attribute are dependent on the associated subprotocol; see <xref target="
prot_att" format="default" sectionFormat="of" derivedContent="Section 5.2"/>.
</t> </t>
<section title="Managing Stream Identifiers" anchor="id_m <section anchor="id_mgmt" numbered="true" removeInRFC="false" toc="include
ngt"> " pn="section-6.1">
<t> <name slugifiedName="name-managing-stream-identifiers">Managing Stream I
dentifiers</name>
In order to avoid SCTP Stream identifier collisio <t indent="0" pn="section-6.1-1">
ns, in alignment with <xref target="I-D.ietf-rtcweb-data-protocol"/>, the endpoi In order to avoid SCTP Stream identifier collisions, in alignment with
nt acting as DTLS client (for <xref target="RFC8832" format="default" sectionFormat="of" derivedConten
the SCTP association used to realize data channels) MUST use even identifier val t="RFC8832"/>, the endpoint acting as a DTLS client (for
ues, the SCTP association used to realize data channels) <bcp14>MUST</bcp14> use even
and the endpoint acting as DTLS server MUST use odd identifier values. </t> identifier values,
<t>SCTP stream identifiers associated with data c and the endpoint acting as a DTLS server <bcp14>MUST</bcp14> use odd identifier
hannels that have been negotiated using DCEP MUST NOT be included in SDP offers values. </t>
and answers. <t indent="0" pn="section-6.1-2">SCTP stream identifiers associated with
</t> data channels that have been negotiated using DCEP <bcp14>MUST NOT</bcp14> be i
</section> ncluded in SDP offers and answers.
<!-- id_mngt --> </t>
<section title="Negotiating Data Channel Parameters" anch </section>
or="param_negotiation"> <section anchor="param_negotiation" numbered="true" removeInRFC="false" to
<t> c="include" pn="section-6.2">
The data channel types defined in <xref target="I-D.ietf-rtcweb-data-protocol <name slugifiedName="name-negotiating-data-channel-pa">Negotiating Data
"/> are Channel Parameters</name>
mapped to the dcmap SDP attribute parameters in the following manner where "o <t indent="0" pn="section-6.2-1">
rdered=true" is the default and may be omitted: The data channel types defined in <xref target="RFC8832" format="default" sec
tionFormat="of" derivedContent="RFC8832"/> are
mapped to the dcmap SDP attribute parameters in the following manner, where "
ordered=true" is the default and may be omitted:
</t> </t>
<t> <sourcecode name="data-channel-items" type="sdp" markers="false" pn="sec
<figure align="left" title=""> tion-6.2-2">
<artwork align="left"><![CDATA[
DATA_CHANNEL_RELIABLE DATA_CHANNEL_RELIABLE
ordered=true ordered=true
DATA_CHANNEL_RELIABLE_UNORDERED DATA_CHANNEL_RELIABLE_UNORDERED
ordered=false ordered=false
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT
ordered=true;max-retr=<number of retransmissions&gt; ordered=true;max-retr=&lt;number of retransmissions&gt;
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED
ordered=false;max-retr=<number of retransmissions&gt; ordered=false;max-retr=&lt;number of retransmissions&gt;
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED
ordered=true;max-time=<lifetime in milliseconds&gt; ordered=true;max-time=&lt;lifetime in milliseconds&gt;
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED
ordered=false;max-time=<lifetime in milliseconds> ordered=false;max-time=&lt;lifetime in milliseconds&gt;</sourcecode>
]]></artwork> <t indent="0" pn="section-6.2-3">
</figure> By definition, 'max-retr' and 'max-time' are mutually exclusive,
</t> so both <bcp14>MUST NOT</bcp14> be present in the "a=dcmap:" attribute
<t> line. If an SDP offer contains both of these parameters, then the
By definition max-retr and max-time are mutually exclusive, receiver of such an SDP offer <bcp14>MUST</bcp14> reject the SDP offer. If a
so both MUST NOT be present in the "a=dcmap:" attribute n SDP
line. If an SDP offer contains both of these parameters then the answer contains both of these parameters, then the offerer <bcp14>MUST</bcp14
receiver of such an SDP offer MUST reject the SDP offer. If an SDP > treat
answer contains both of these parameters then the offerer MUST treat
the associated SDP offer/answer as failed. </t> the associated SDP offer/answer as failed. </t>
</section> </section>
<!-- ="Negotiating Data Channel Parameters" --> <section anchor="opendc" numbered="true" removeInRFC="false" toc="include"
<section title="Generating the Initial Offer for A Data C pn="section-6.3">
hannel" anchor="opendc"> <name slugifiedName="name-generating-the-initial-offe">Generating the In
<t>When an offerer sends an initial offer, in ord itial Offer for a Data Channel</name>
er to negotiate an SCTP stream for a data channel, the offerer: <t indent="0" pn="section-6.3-1">When an offerer sends an initial offer,
in order to negotiate an SCTP stream for a data channel, the offerer
<list style="symbols">
<t>SHALL include an SDP dcmap att
ribute (<xref target="sdp_synt"/> and <xref target="param_negotiation"/>) assoc
iated with the data channel in the “m=” section representing the SCTP associatio
n used to realize the data channel; and
</t>
<t>MAY include one or more SDP dc
sa attributes (<xref target="prot_att"/>) associated with the
data channel. The value of the stream-id part of each attribute SHALL matc
h the dcmap-stream-id value of the dcmap attribute.
</t>
</list>
</t>
</section>
<section title="Generating SDP Answer">
<t>When an answerer receives an offer that includ
es an “m=" section for an SCTP association, that describes an SCTP stream for a
data channel, if the answerer accepts the data channel it:
<list style="symbols"> </t>
<t>SHALL include an SDP dcmap att <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
ribute (<xref target="sdp_synt"/> and <xref target="param_negotiation"/>) .3-2">
<li pn="section-6.3-2.1">
<bcp14>SHALL</bcp14> include an SDP dcmap attribute
(Sections <xref target="subsec-sdp-attr-for-dc-par-neg" format="counte
r" sectionFormat="of" derivedContent="5.1"/> and <xref target="param_negotiatio
n" format="counter" sectionFormat="of" derivedContent="6.2"/>) associated with t
he data channel in the "m=" section representing the SCTP association used to re
alize the data channel, and
</li>
<li pn="section-6.3-2.2">
<bcp14>MAY</bcp14> include one or more SDP dcsa attributes (<xref ta
rget="prot_att" format="default" sectionFormat="of" derivedContent="Section 5.2"
/>) associated with the
data channel. The value of the 'stream-id' part of each attribute <bcp14>S
HALL</bcp14> match the 'dcmap-stream-id' value of the dcmap attribute.
</li>
</ul>
</section>
<section numbered="true" removeInRFC="false" toc="include" pn="section-6.4
">
<name slugifiedName="name-generating-the-sdp-answer">Generating the SDP
Answer</name>
<t indent="0" pn="section-6.4-1">When an answerer receives an offer that
includes an "m=" section
for an SCTP association, the offer describes an SCTP stream for a data c
hannel, if the answerer accepts the data channel, it
</t>
<ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
.4-2">
<li pn="section-6.4-2.1">
<bcp14>SHALL</bcp14> include an SDP dcmap attribute
(Sections <xref target="subsec-sdp-attr-for-dc-par-neg" format="counte
r" sectionFormat="of" derivedContent="5.1"/> and <xref target="param_negotiatio
n" format="counter" sectionFormat="of" derivedContent="6.2"/>)
associated associated
with the data channel in the "m=" section representing the SCTP association used with the data channel in the "m=" section representing the SCTP association used
to realize the data channel. The value of the dcmap-stream-id, max-retr and max- to realize the data channel. The value of the 'dcmap-stream-id', 'max-retr', and
time 'max-time'
values of the dcmap attribute SHALL be identical to the value used for the data values of the dcmap attribute <bcp14>SHALL</bcp14> be identical to the value use
channel d for the data channel
in the offer; and in the offer, and
</li>
</t> <li pn="section-6.4-2.2">
<t>MAY include one or more SDP dc <bcp14>MAY</bcp14> include one or more SDP dcsa attributes (<xref ta
sa attributes (<xref target="prot_att"/>) associated with the rget="prot_att" format="default" sectionFormat="of" derivedContent="Section 5.2"
/>) associated with the
data channel. data channel.
</t> </li>
</list> </ul>
</t> </section>
</section> <section numbered="true" removeInRFC="false" toc="include" pn="section-6.5
<section title="Offerer Processing of the SDP Answer"> ">
<t>An offerer receiving an SDP answer performs th <name slugifiedName="name-offerer-processing-of-the-s">Offerer Processin
e following: g of the SDP Answer</name>
<t indent="0" pn="section-6.5-1">An offerer receiving an SDP answer perf
orms the following:
<list style="symbols"> </t>
<t>SHALL close any created data c <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
hannels as described in .5-2">
<xref target="close-dc"/> <li pn="section-6.5-2.1">It <bcp14>SHALL</bcp14> close any created dat
a channels as described in
<xref target="close-dc" format="default" sectionFormat="of" derivedConten
t="Section 6.6.1"/>
for which the expected "a=dcmap:" attributes are not for which the expected "a=dcmap:" attributes are not
present in the SDP answer. If the SDP answer has no "a=dcmap" attribute e present in the SDP answer. If the SDP answer has no "a=dcmap:" attributes
ither the peer does not support "a=dcmap:" attributes or , either the peer does not support "a=dcmap:" attributes or
it rejected all the data channels. In either case the offerer closes it rejected all the data channels. In either case, the offerer
all the SDP offered closes all the data channels offered by SDP that were open at the ti
data channels that were open at the time of offer. me of the offer.
The DTLS association and SCTP association will still be setup. At th The DTLS association and SCTP association will still be set up. At t
is his
point the offerer may use DCEP negotiation <xref target="I-D.ietf-rtcweb-data point, the offerer may use DCEP negotiation <xref target="RFC8832" format="de
-protocol"/> to open data channels</t> fault" sectionFormat="of" derivedContent="RFC8832"/> to open data channels.</li>
</list> </ul>
</t> <t indent="0" pn="section-6.5-3">Each agent application <bcp14>MUST</bcp
<t>Each agent application MUST wait to send data 14> wait to send data until it has
until it has
confirmation that the data channel at the peer is instantiated. confirmation that the data channel at the peer is instantiated.
For WebRTC, this is when both data channel stacks have channel For WebRTC, this is when both data channel stacks have channel
parameters instantiated. This occurs: parameters instantiated and occurs as follows:
<list style="symbols"> </t>
<t>At both peers when a data chan <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
nel is created without a previously .5-4">
<li pn="section-6.5-4.1">At both peers when a data channel is created
without a previously
established SCTP association, as soon as the SCTP association established SCTP association, as soon as the SCTP association
is successfully established.</t> is successfully established.</li>
<t>At the agent receiving an SDP <li pn="section-6.5-4.2">At the agent receiving an SDP offer for which
offer for which there is an there is an
established SCTP association, as soon as it creates the established SCTP association, as soon as it creates the
negotiated data channel based on information negotiated data channel based on information
signaled in the SDP offer.</t> signaled in the SDP offer.</li>
<t>At the agent sending an SDP of <li pn="section-6.5-4.3">At the agent sending an SDP offer to create a
fer to create a new data channel for which there is an established SCTP new data channel for which there is an established SCTP
association, when it receives the SDP answer confirming acceptance association, when it receives the SDP answer confirming acceptance
of the data channel or when it begins to receive data on the of the data channel or when it begins to receive data on the
data channel from the peer, whichever occurs first.</t> data channel from the peer, whichever occurs first.</li>
</list> </ul>
</t> </section>
</section> <section numbered="true" removeInRFC="false" toc="include" pn="section-6.6
<!-- opendc --> ">
<section title="Modifying the Session"> <name slugifiedName="name-modifying-the-session">Modifying the Session</
<t>When an offer sends a subsequent offer, that i name>
ncludes information for <t indent="0" pn="section-6.6-1">When an offerer sends a subsequent offe
r that includes information for
a previously negotiated data channel, unless the offerer intends to a previously negotiated data channel, unless the offerer intends to
close the data channel (<xref target="close-dc"/>), the offerer SHALL include the close the data channel (<xref target="close-dc" format="default" sectionForma t="of" derivedContent="Section 6.6.1"/>), the offerer <bcp14>SHALL</bcp14> inclu de the
previously negotiated SDP attributes and attribute values associated with the previously negotiated SDP attributes and attribute values associated with the
data channel. The answerer may reject the offer. The means for rejecting an o ffer are dependent on data channel. The answerer may reject the offer. The means for rejecting an o ffer are dependent on
the higher layer protocol. The offer/answer exchange is atomic; if the answe the higher-layer protocol. The offer/answer exchange is atomic; if the answe
r is rejected, the session reverts to the state prior to the r is rejected, the session reverts to the state prior to the
offer <xref target="RFC3264"/>. offer <xref target="RFC3264" format="default" sectionFormat="of" derivedConte
nt="RFC3264"/>.
</t>
<section title="Closing a Data Channel" anchor="c
lose-dc">
<t>In order to close a data channel, the
endpoint that wants to close
SHALL send the SCTP SSN reset message <xref target="RFC6525"/>, following the
procedures in section 6.7 of <xref target="I-D.ietf-rtcweb-data-channel"/>.
In addition, if the closed data channel was negotiated using the offer/answer me </t>
chanism <xref target="opendc"/>, the endpoint that closed the data channel SHALL <section anchor="close-dc" numbered="true" removeInRFC="false" toc="incl
send a subsequent offer in which it either: ude" pn="section-6.6.1">
<name slugifiedName="name-closing-a-data-channel">Closing a Data Chann
el</name>
<t indent="0" pn="section-6.6.1-1">In order to close a data channel, t
he endpoint that wants to
close the data channel
<bcp14>SHALL</bcp14> send an SCTP SSN Reset message <xref target="RFC6525" fo
rmat="default" sectionFormat="of" derivedContent="RFC6525"/>, following the proc
edure in <xref target="RFC8831" sectionFormat="of" section="6.7" format="default
" derivedLink="https://rfc-editor.org/rfc/rfc8831#section-6.7" derivedContent="R
FC8831"/>.
In addition, if the closed data channel was negotiated using the offer/answer
mechanism (<xref target="opendc" format="default" sectionFormat="of" derivedCont
ent="Section 6.3"/>), the endpoint that closed the data channel
<bcp14>SHALL</bcp14> send a subsequent offer in which it does one of the followi
ng:
</t> </t>
<t> <ul spacing="normal" bare="false" empty="false" indent="3" pn="section
<list style="symbols"> -6.6.1-2">
<t> <li pn="section-6.6.1-2.1">Removes the SDP dcmap attribute and SDP d
removes the SDP dcmap attribute and SDP dcsa attributes associated with the c csa attributes
losed data channel. Once the endpoint receives a successful answer, the SCTP str associated with the closed data channel. Once the endpoint
eam identifier value can later be used for a new data channel (negotiated using receives a successful answer, the SCTP stream identifier value can
DCTP or using the offer/answer mechanism); or</t> later be used for a new data channel (negotiated using either SCTP
<t>after a reset has been or the offer/answer mechanism), or
performed re-uses the SCTP stream used for the closed data channel for a new da </li>
ta channel, using the procedures in <xref target="opendc"/>. The offerer SHALL u <li pn="section-6.6.1-2.2">After a reset has been performed, reuses
se a different SDP dcmap attribute value for the data channel using the same SCT the SCTP stream used for the closed data channel for a new data channel, followi
P stream. ng the procedure in <xref target="opendc" format="default" sectionFormat="of" de
rivedContent="Section 6.3"/>. The offerer <bcp14>SHALL</bcp14> use a different S
</t> DP dcmap attribute value for the data channel using the same SCTP stream.
</list> </li>
</t> </ul>
</section> </section>
<!-- Closing a Data Channel --> </section>
</section> <section anchor="various_SDP_OA_considerations" numbered="true" removeInRF
<section title="Various SDP Offer/Answer Considerations" C="false" toc="include" pn="section-6.7">
anchor="various_SDP_OA_considerations"> <name slugifiedName="name-various-sdp-offer-answer-co">Various SDP Offer
<t> /Answer Considerations</name>
<list> <t indent="0" pn="section-6.7-1">An SDP offer or answer has no "a=dcmap:
<t>An SDP offer or answer has no " attributes but has "a=dcsa:" attributes:
"a=dcmap:" attributes but has "a=dcsa:" attributes. </t>
<list style="symbols"> <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
<t>This is consid .7-2">
ered an error case. In this case the receiver of such an <li pn="section-6.7-2.1">This is considered an error case. In this cas
SDP offer or answer MUST discard this "a=dcsa:" attributes. e, the receiver of such an
</t> SDP offer or answer <bcp14>MUST</bcp14> discard the "a=dcsa:" attrib
</list> utes.
</t> </li>
<t>SDP offer or answer has an "a= </ul>
dcsa" attribute, whose subprotocol attribute <t indent="0" pn="section-6.7-3">An SDP offer or answer has an "a=dcsa:"
is unknown. attribute whose subprotocol attribute
<list style="symbols"> is unknown:
<t>The receiver o </t>
f such an SDP offer or answer SHOULD ignore this <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
entire "a=dcsa" attribute line. .7-4">
</t> <li pn="section-6.7-4.1">The receiver of such an SDP offer or answer <
</list> bcp14>SHOULD</bcp14> ignore this
</t> entire "a=dcsa:" attribute line.
<t>SDP offer or answer has an "a= </li>
dcsa" attribute, whose subprotocol attribute </ul>
is known, but whose subprotocol attribute semantic is not known for the <t indent="0" pn="section-6.7-5">An SDP offer or answer has an "a=dcsa:"
data channel transport case. attribute whose subprotocol attribute
<list style="symbols"> is known but whose subprotocol attribute semantic is not known for the
<t>The receiver o data channel transport case:
f such an SDP offer or answer SHOULD ignore this </t>
entire "a=dcsa" attribute line. <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-6
</t> .7-6">
</list> <li pn="section-6.7-6.1">The receiver of such an SDP offer or answer <
</t> bcp14>SHOULD</bcp14> ignore this
</list> entire "a=dcsa:" attribute line.
</t> </li>
</section> </ul>
<!-- various SDP offer/answer ... --> </section>
</section> </section>
<!-- Procedures --> <section anchor="examples" numbered="true" removeInRFC="false" toc="include"
<section title="Examples" anchor="examples"> pn="section-7">
<figure align="left" title="Example 1" anchor="example1"> <name slugifiedName="name-examples">Examples</name>
<artwork align="left"><![CDATA[ <t indent="0" pn="section-7-1"><xref target="example1" format="default" se
SDP offer: ctionFormat="of" derivedContent="Figure 1"/> shows an example of an SDP offer an
d answer
where the SDP answerer rejects the data channel
with stream id 0 either for explicit reasons or because it does not
understand the "a=dcmap:" attribute.
As a result, the offerer will close the data channel created with the
SDP offer/answer negotiation option.
The SCTP association will still be set up over DTLS.
At this point, the offerer or the answerer may use DCEP negotiation to open d
ata
channels.</t>
<figure anchor="example1" align="left" suppress-title="false" pn="figure-1
">
<name slugifiedName="name-example-1">Example 1</name>
<sourcecode name="example-1-sdp-offer" type="sdp" markers="false" pn="se
ction-7-2.1">
m=application 10001 UDP/DTLS/SCTP webrtc-datachannel m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP6 2001:db8::3 c=IN IP6 2001:db8::3
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5000 a=sctp-port:5000
a=setup:actpass a=setup:actpass
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
a=tls-id:abc3de65cddef001be82 a=tls-id:abc3de65cddef001be82
a=dcmap:0 subprotocol="bfcp";label="bfcp" a=dcmap:0 subprotocol="bfcp";label="bfcp"</sourcecode>
<sourcecode name="example-1-sdp-answer" type="sdp" markers="false" pn="s
SDP answer: ection-7-2.2">
m=application 10002 UDP/DTLS/SCTP webrtc-datachannel m=application 10002 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP6 2001:db8::1 c=IN IP6 2001:db8::1
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5002 a=sctp-port:5002
a=setup:passive a=setup:passive
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
a=tls-id:dcb3ae65cddef0532d42 a=tls-id:dcb3ae65cddef0532d42</sourcecode>
]]></artwork> </figure>
</figure> <t indent="0" pn="section-7-3"><xref target="example2" format="default" se
<t>In the example in <xref target="example1"/> the SDP an ctionFormat="of" derivedContent="Figure 2"/> shows an example of an SDP offer an
swerer rejected the data channel d answer
with stream id 0 either for explicit reasons or because it does not where the SDP offer contains data channels for BFCP and
understand the "a=dcmap:" attribute. MSRP subprotocols. The SDP answer rejects BFCP and accepts MSRP.
As a result the offerer will close the data channel created with the So, the offerer closes the data channel for BFCP, and both the offerer
SDP offer/answer negotiation option. and the answerer may start using the MSRP data channel
The SCTP association will still be setup over DTLS. (after the SCTP association is set up).
At this point the offerer or the answerer may use DCEP negotiation to open da The data channel with stream id 0 is free and can be used for future
ta DCEP or SDP offer/answer negotiation.</t>
channels.</t> <figure anchor="example2" align="left" suppress-title="false" pn="figure-2
<figure align="left" title="Example 2" anchor="example2"> ">
<artwork align="left"><![CDATA[ <name slugifiedName="name-example-2">Example 2</name>
SDP offer: <sourcecode name="example-2-sdp-offer" type="sdp" markers="false" pn="se
ction-7-4.1">
m=application 10001 UDP/DTLS/SCTP webrtc-datachannel m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5000 a=sctp-port:5000
a=setup:actpass a=setup:actpass
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
a=tls-id:abc3de65cddef001be82 a=tls-id:abc3de65cddef001be82
a=dcmap:0 subprotocol="bfcp";label="bfcp" a=dcmap:0 subprotocol="bfcp";label="bfcp"
a=dcmap:2 subprotocol="msrp";label="msrp" a=dcmap:2 subprotocol="msrp";label="msrp"
a=dcsa:2 accept-types:message/cpim text/plain a=dcsa:2 accept-types:message/cpim text/plain
a=dcsa:2 path:msrp://alice.example.com:10001/2s93i93idj;dc a=dcsa:2 path:msrp://alice.example.com:10001/2s93i93idj;dc</sourcecode>
<sourcecode name="example-2-sdp-answer" type="sdp" markers="false" pn="s
SDP answer: ection-7-4.2">
m=application 10002 UDP/DTLS/SCTP webrtc-datachannel m=application 10002 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.2 c=IN IP4 192.0.2.2
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5002 a=sctp-port:5002
a=setup:passive a=setup:passive
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
a=tls-id:dcb3ae65cddef0532d42 a=tls-id:dcb3ae65cddef0532d42
a=dcmap:2 subprotocol="msrp";label="msrp" a=dcmap:2 subprotocol="msrp";label="msrp"
a=dcsa:2 accept-types:message/cpim text/plain a=dcsa:2 accept-types:message/cpim text/plain
a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc a=dcsa:2 path:msrp://bob.example.com:10002/si438dsaodes;dc</sourcecode>
]]></artwork> </figure>
</figure> <t indent="0" pn="section-7-5">The example in <xref target="example3" form
<t>In the example in <xref target="example2"/> the SDP of at="default" sectionFormat="of" derivedContent="Figure 3"/> is a continuation of
fer contains data channels for BFCP the example in <xref target="example2" format="default" sectionFormat="of" deri
(Binary Floor Control Protocol) and vedContent="Figure 2"/>.
MSRP subprotocols. The SDP answer rejected BFCP and accepted MSRP. The SDP offerer now removes the MSRP data channel with stream id 2
So, the offerer closes the data channel for BFCP and both offerer but opens a new MSRP data channel with stream id 4.
and answerer may start using the MSRP data channel The answerer accepts the entire offer.
(after the SCTP association is set up). As a result, the offerer closes the previously negotiated MSRP-related data c
The data channel with stream id 0 is free and can be used for future hannel,
DCEP or SDP offer/answer negotiation.</t> and both the offerer and the answerer may start using the new MSRP-related da
<t>Continuing the example in <xref target="example2"/>.</ ta
t> channel.</t>
<figure align="left" title="Example 3" anchor="example3"> <figure anchor="example3" align="left" suppress-title="false" pn="figure-3
<artwork align="left"><![CDATA[ ">
Subsequent SDP offer: <name slugifiedName="name-example-3">Example 3</name>
<sourcecode name="example-3-sdp-offer" type="sdp" markers="false" pn="se
ction-7-6.1">
m=application 10001 UDP/DTLS/SCTP webrtc-datachannel m=application 10001 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5000 a=sctp-port:5000
a=setup:actpass a=setup:actpass
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
a=tls-id:abc3de65cddef001be82 a=tls-id:abc3de65cddef001be82
a=dcmap:4 subprotocol="msrp";label="msrp" a=dcmap:4 subprotocol="msrp";label="msrp"
a=dcsa:4 accept-types:message/cpim text/plain a=dcsa:4 accept-types:message/cpim text/plain
a=dcsa:4 path:msrp://alice.example.com:10001/2s93i93idj;dc a=dcsa:4 path:msrp://alice.example.com:10001/2s93i93idj;dc</sourcecode>
<sourcecode name="example-3-sdp-answer" type="sdp" markers="false" pn="s
Subsequent SDP answer: ection-7-6.2">
m=application 10002 UDP/DTLS/SCTP webrtc-datachannel m=application 10002 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.2 c=IN IP4 192.0.2.2
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5002 a=sctp-port:5002
a=setup:passive a=setup:passive
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA 5B:AD:67:B1:3E:82:AC:3B:90:02:B1:DF:12:5D:CA:6B:3F:E5:54:FA
a=tls-id:dcb3ae65cddef0532d42 a=tls-id:dcb3ae65cddef0532d42
a=dcmap:4 subprotocol="msrp";label="msrp" a=dcmap:4 subprotocol="msrp";label="msrp"
a=dcsa:4 accept-types:message/cpim text/plain a=dcsa:4 accept-types:message/cpim text/plain
a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc a=dcsa:4 path:msrp://bob.example.com:10002/si438dsaodes;dc</sourcecode>
]]></artwork> </figure>
</figure> </section>
<t>The example in <xref target="example3"/> is a continua <section anchor="sec-cons" numbered="true" removeInRFC="false" toc="include"
tion of the example in <xref target="example2"/>. pn="section-8">
The SDP offerer now removes the MSRP data channel with stream id 2, <name slugifiedName="name-security-considerations">Security Considerations
but opens a new MSRP data channel with stream id 4. </name>
The answerer accepts the entire offer. <t indent="0" pn="section-8-1">This document specifies new SDP attributes
As a result the offerer closes the earlier negotiated MSRP related data chann used in the negotiation of data channel parameters. </t>
el <t indent="0" pn="section-8-2">
and both offerer and answerer may start using new the MSRP related data chann These parameters are negotiated as part of opening an SCTP channel over DTLS as
el.</t> specified in <xref target="RFC8841" format="default" sectionFormat="of" derivedC
</section> ontent="RFC8841"/>. Each
<!-- Examples --> subprotocol may come with its own security considerations that need to be docume
<section title="Security Considerations" anchor="sec-cons"> nted as part of the subprotocol definition.
<t>This document specifies new SDP attributes used in the Otherwise, this document does not add any security considerations to those speci
negotiation of the DATA channel parameters. </t> fied in <xref target="RFC8841" format="default" sectionFormat="of" derivedConten
<t> t="RFC8841"/>.
These parameter are negotiated as part of opening a SCTP channel over DTLS as sp </t>
ecified in <xref target="I-D.ietf-mmusic-sctp-sdp"/>. Each <t indent="0" pn="section-8-3">Error cases such as the use of unknown para
subprotocol may come with it’s own security considerations that need to be docum meter values or violations
ented as part of the subprotocol definition. of the odd/even rule (<xref target="id_mgmt" format="default" sectionForma
Otherwise this document does not add any security considerations to the ones spe t="of" derivedContent="Section 6.1"/>) <bcp14>MUST</bcp14>
cified in <xref target="I-D.ietf-mmusic-sctp-sdp"/> be handled by closing the corresponding data channel.</t>
</t> </section>
<t>Error cases like the use of unknown parameter values o <section anchor="IANA" numbered="true" removeInRFC="false" toc="include" pn=
r violation the odd/even rule MUST "section-9">
be handled by closing the corresponding Data Channel.</t> <name slugifiedName="name-iana-considerations">IANA Considerations</name>
</section> <section anchor="IANA_subproto_ids" numbered="true" removeInRFC="false" to
<section title="IANA Considerations" anchor="IANA"> c="include" pn="section-9.1">
<section title="Subprotocol Identifiers" anchor="IANA_sub <name slugifiedName="name-subprotocol-identifiers">Subprotocol Identifie
proto_ids"> rs</name>
<t>Registration of new subprotocol identifiers is <t indent="0" pn="section-9.1-1">Registration of new subprotocol identif
performed using the existing IANA iers is performed using the existing IANA
"WebSocket Subprotocol Name Registry" table.</t> "WebSocket Subprotocol Name Registry" table.</t>
<t>The following text should be added following t <t indent="0" pn="section-9.1-2">The following text has been added below
he title of the table.</t> the title of the table.</t>
<t>"This table also includes subprotocol identifi <t indent="0" pn="section-9.1-3">"This table also includes subprotocol i
ers specified for usage within a dentifiers specified for usage within a
WebRTC data channel."</t> WebRTC data channel."</t>
<t>The following reference should be added to und <t indent="0" pn="section-9.1-4">This document (RFC 8864) has been added
er the heading reference: to the "Reference" list for
"RFC XXXX".</t> the registry.</t>
<t>This document assigns no new values to this ta <t indent="0" pn="section-9.1-5">This document assigns no new values to
ble.</t> this table.</t>
<t>A subprotocol may simultaneously be defined fo <t indent="0" pn="section-9.1-6">A subprotocol may simultaneously be def
r data channel transport ined for data channel transport
and for Websocket transport. and for WebSocket transport.
In such a case the "Subprotocol Definition" and "Reference" cells in the In such a case, the "Subprotocol Definition" and "Reference" cells in the
subprotocol's row of the IANA "WebSocket Subprotocol Name Registry" table sh ould subprotocol's row of the IANA "WebSocket Subprotocol Name Registry" table sh ould
contain two entries. contain two entries.
One entry in each of these cells should refer to the Websocket related One entry in each of these cells should refer to the WebSocket-related
subprotocol specification, and the other entry should refer to the data subprotocol specification, and the other entry should refer to the
channel related subprotocol specification. data-channel-related subprotocol specification.
</t> </t>
<t>NOTE to RFC Editor: Please replace "XXXX" with </section>
the number of this RFC.</t> <section numbered="true" removeInRFC="false" toc="include" pn="section-9.2
</section> ">
<section title="New SDP Attributes"> <name slugifiedName="name-new-sdp-attributes">New SDP Attributes</name>
<section title="dcmap" anchor="IANA-reg-dcmap"> <section anchor="IANA-reg-dcmap" numbered="true" removeInRFC="false" toc
<t>NOTE to RFC Editor: Please replace "XX ="include" pn="section-9.2.1">
XX" with the number of this RFC.</t> <name slugifiedName="name-dcmap">dcmap</name>
<t>This document defines a new SDP media- <t indent="0" pn="section-9.2.1-1">This document defines a new SDP med
level attribute "a=dcmap:" as follows: ia-level attribute, "a=dcmap:", as follows:
</t> </t>
<texttable title=""> <table anchor="dcmap-iana" align="center" pn="table-3">
<ttcol align="left" width="35%"/> <name slugifiedName="name-new-adcmap-attribute">New "a=dcmap:" Attri
<ttcol align="left" width="65%"/> bute</name>
<c>Contact name:</c> <thead>
<c>IESG</c> <tr>
<c>Contact email:</c> <th colspan="2" align="center" rowspan="1">"a=dcmap:"</th>
<c>iesg@ietf.org</c> </tr>
<c>Attribute name:</c> </thead>
<c>dcmap</c> <tbody>
<c>Attribute syntax:</c> <tr>
<c>As per <xref target="dcmap-att <td align="left" colspan="1" rowspan="1">Contact name</td>
r-definition"/> <td align="left" colspan="1" rowspan="1">IESG</td>
</c> </tr>
<c>Attribute semantics:</c> <tr>
<c>As per <xref target="dcmap-att <td align="left" colspan="1" rowspan="1">Contact email</td>
r-definition"/> <td align="left" colspan="1" rowspan="1">iesg@ietf.org</td>
</c> </tr>
<c>Usage level:</c> <tr>
<c>media</c> <td align="left" colspan="1" rowspan="1">Attribute name</td>
<c>Charset dependent:</c> <td align="left" colspan="1" rowspan="1">dcmap</td>
<c>No</c> </tr>
<c>Purpose:</c> <tr>
<c>Define data channel specific p <td align="left" colspan="1" rowspan="1">Attribute syntax</td>
arameters</c> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<c>Appropriate values:</c> map-attr-definition" format="default" sectionFormat="of" derivedContent="Section
<c>As per <xref target="dcmap-att 5.1.1"/>
r-definition"/> </td>
</c> </tr>
<c>O/A procedures:</c> <tr>
<c>As per <xref target="section_p <td align="left" colspan="1" rowspan="1">Attribute semantics</td
rocedures"/> >
</c> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<c>Mux category:</c> map-attr-definition" format="default" sectionFormat="of" derivedContent="Section
<c>SPECIAL. See <xref target="dcm 5.1.1"/>
ap-mux-category"/> </td>
</c> </tr>
<c>Reference:</c> <tr>
<c>RFCXXXX</c> <td align="left" colspan="1" rowspan="1">Usage level</td>
</texttable> <td align="left" colspan="1" rowspan="1">media</td>
</section> </tr>
<section title="dcsa" anchor="IANA-reg-dcsa"> <tr>
<t>NOTE to RFC Editor: Please replace "XX <td align="left" colspan="1" rowspan="1">Charset dependent</td>
XX" with the number of this RFC.</t> <td align="left" colspan="1" rowspan="1">No</td>
<t>This document defines a new SDP media- </tr>
level attribute "a=dcsa:" as follows: <tr>
</t> <td align="left" colspan="1" rowspan="1">Purpose</td>
<texttable title=""> <td align="left" colspan="1" rowspan="1">To define data-channel-
<ttcol align="left" width="35%"/> specific parameters</td>
<ttcol align="left" width="65%"/> </tr>
<c>Contact name:</c> <tr>
<c>IESG</c> <td align="left" colspan="1" rowspan="1">Appropriate values</td>
<c>Contact email:</c> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<c>iesg@ietf.org</c> map-attr-definition" format="default" sectionFormat="of" derivedContent="Section
<c>Attribute name:</c> 5.1.1"/>
<c>dcsa</c> </td>
<c>Attribute syntax:</c> </tr>
<c>As per <xref target="dcsa-attr <tr>
ibute"/> <td align="left" colspan="1" rowspan="1">O/A procedures</td>
</c> <td align="left" colspan="1" rowspan="1">SDP offer/answer proced
<c>Attribute semantics:</c> ures as per <xref target="section_procedures" format="default" sectionFormat="of
<c>As per <xref target="dcsa-attr " derivedContent="Section 6"/>
ibute"/> </td>
</c> </tr>
<c>Usage level:</c> <tr>
<c>media</c> <td align="left" colspan="1" rowspan="1">Mux category</td>
<c>Charset dependent:</c> <td align="left" colspan="1" rowspan="1">SPECIAL. See <xref targ
<c>No</c> et="dcmap-mux-category" format="default" sectionFormat="of" derivedContent="Sect
<c>Purpose:</c> ion 5.1.9"/>
<c>Define data channel subprotoco </td>
l specific attributes</c> </tr>
<c>Appropriate values:</c> <tr>
<c>As per <xref target="dcsa-attr <td align="left" colspan="1" rowspan="1">Reference</td>
ibute"/> <td align="left" colspan="1" rowspan="1">RFC 8864</td>
</c> </tr>
<c>O/A procedures:</c> </tbody>
<c>As per <xref target="section_p </table>
rocedures"/> </section>
</c> <section anchor="IANA-reg-dcsa" numbered="true" removeInRFC="false" toc=
<c>Mux category:</c> "include" pn="section-9.2.2">
<c>SPECIAL. See <xref target="dcs <name slugifiedName="name-dcsa">dcsa</name>
a-mux-category"/> <t indent="0" pn="section-9.2.2-1">This document defines a new SDP med
</c> ia-level attribute, "a=dcsa:", as follows:
<c>Reference:</c> </t>
<c>RFCXXXX</c> <table anchor="dcsa-iana" align="center" pn="table-4">
</texttable> <name slugifiedName="name-new-adcsa-attribute">New "a=dcsa:" Attribu
</section> te</name>
</section> <thead>
</section> <tr>
<section title="Contributors"> <th colspan="2" align="center" rowspan="1">"a=dcsa:"</th>
<t>Juergen Stoetzer-Bradler co-authored this document.</t </tr>
> </thead>
</section> <tbody>
<section title="Acknowledgments"> <tr>
<t>The authors wish to acknowledge the borrowing of ideas <td align="left" colspan="1" rowspan="1">Contact name</td>
from other <td align="left" colspan="1" rowspan="1">IESG</td>
internet drafts by Salvatore Loreto, Gonzalo Camarillo, Peter Dunkley </tr>
and Gavin Llewellyn, and to thank Flemming Andreasen, Christian Groves, <tr>
Gunnar Hellstrom, Paul Kyzivat, Jonathan Lennox, <td align="left" colspan="1" rowspan="1">Contact email</td>
Uwe Rauschenbach and Roman Shpount for their invaluable comments.</t> <td align="left" colspan="1" rowspan="1">iesg@ietf.org</td>
<t>Special thanks to Christer Holmberg for helping finish </tr>
the document and cleaning the SDP offer/answer section.</t> <tr>
</section> <td align="left" colspan="1" rowspan="1">Attribute name</td>
<section title="CHANGE LOG"> <td align="left" colspan="1" rowspan="1">dcsa</td>
<section title="Changes against 'draft-ietf-mmusic-data-c </tr>
hannel-sdpneg-15'"> <tr>
<t> <td align="left" colspan="1" rowspan="1">Attribute syntax</td>
<list style="symbols"> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<t>Editorial changes separate se sa-attribute" format="default" sectionFormat="of" derivedContent="Section 5.2.1"
ctions for offer/answer procedures.</t> />
<t>Update security section.</t> </td>
</list> </tr>
</t> <tr>
</section> <td align="left" colspan="1" rowspan="1">Attribute semantics</td
<section title="Changes against 'draft-ietf-mmusic-data-c >
hannel-sdpneg-14'"> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<t> sa-attribute" format="default" sectionFormat="of" derivedContent="Section 5.2.1"
<list style="symbols"> />
<t>Change "dtls-id" to "tls-id" a </td>
nd assign 20 octet long values</t> </tr>
<t>Remove of RFC4566bis draft fro <tr>
m list of normative references. <td align="left" colspan="1" rowspan="1">Usage level</td>
</t> <td align="left" colspan="1" rowspan="1">media</td>
</list> </tr>
</t> <tr>
</section> <td align="left" colspan="1" rowspan="1">Charset dependent</td>
<section title="Changes against 'draft-ietf-mmusic-data-c <td align="left" colspan="1" rowspan="1">No</td>
hannel-sdpneg-12'"> </tr>
<t> <tr>
<list style="symbols"> <td align="left" colspan="1" rowspan="1">Purpose</td>
<t>Modification of Keith's addres <td align="left" colspan="1" rowspan="1">To define attributes th
s information. at are specific to data channel subprotocols</td>
</t> </tr>
</list> <tr>
</t> <td align="left" colspan="1" rowspan="1">Appropriate values</td>
</section> <td align="left" colspan="1" rowspan="1">As per <xref target="dc
<section title="Changes against 'draft-ietf-mmusic-data-c sa-attribute" format="default" sectionFormat="of" derivedContent="Section 5.2.1"
hannel-sdpneg-11'"> />
<t> </td>
<list style="symbols"> </tr>
<t>dcmap-stream-id syntax change <tr>
to limit size to 5 digits. <td align="left" colspan="1" rowspan="1">O/A procedures</td>
</t> <td align="left" colspan="1" rowspan="1">SDP offer/answer proced
<t>Add missing 'x' prefix to quot ures as per <xref target="section_procedures" format="default" sectionFormat="of
ed-visible syntax. " derivedContent="Section 6"/>
</t> </td>
<t>Align SDP offerer and answerer </tr>
handling when both max-retr and max-time are present. <tr>
</t> <td align="left" colspan="1" rowspan="1">Mux category</td>
<t>Use of TEST-NET-1 ip addresses <td align="left" colspan="1" rowspan="1">SPECIAL. See <xref targ
in examples. et="dcsa-mux-category" format="default" sectionFormat="of" derivedContent="Secti
</t> on 5.2.2"/>
<t>Add missing a=dtls-id in one e </td>
xample. </tr>
</t> <tr>
</list> <td align="left" colspan="1" rowspan="1">Reference</td>
</t> <td align="left" colspan="1" rowspan="1">RFC 8864</td>
</section> </tr>
<section title="Changes against 'draft-ietf-mmusic-data-c </tbody>
hannel-sdpneg-10'"> </table>
<t> </section>
<list style="symbols"> </section>
<t>Removal of the "a=connection" <section anchor="IANA-reg-data-channel-attribs" numbered="true" removeInRF
attribute lines from all SDP examples. C="false" toc="include" pn="section-9.3">
</t> <name slugifiedName="name-registering-attributes-for-">Registering Attri
</list> butes for Use with Data Channels</name>
</t> <t indent="0" pn="section-9.3-1">When a subprotocol is defined for use o
</section> ver data channels with
<section title="Changes against 'draft-ietf-mmusic-data-c the SDP offer/answer mechanism, any SDP attributes that may be
hannel-sdpneg-09'"> negotiated using the "a=dcsa:" attribute <bcp14>MUST</bcp14> be added to
<t> the IANA
<list style="symbols"> "attribute-name registry (formerly "att-field")", as specified in
<t>In the introduction: <xref target="RFC8866" sectionFormat="comma" section="8.2.4" format="def
<list style="symbols"> ault" derivedLink="https://rfc-editor.org/rfc/rfc8866#section-8.2.4" derivedCont
<t>Replacement of ent="RFC8866"/>. This
the sentence "The RTCWeb working group has defined the concept of document specifies that new Usage Levels of the form "dcsa (foo)"
bi-directional data channels running on top of SCTP/DTLS (SCTP over the Dat (where "foo" is a placeholder for the subprotocol name) should be
agram registered by documents that specify negotiation of particular
Transport Layer Security protocol)" with "The RTCWeb working group has defi subprotocols.</t>
ned the <t indent="0" pn="section-9.3-2">IANA has updated the "attribute-name (f
concept of bi-directional data channels running on top of the Stream Contro ormerly "att-field")"
l registry to point to this document.</t>
Transmission Protocol (SCTP)". </section>
</t> </section>
<t>Addition of fo </middle>
llowing sentences to the second paragraph: "These procedures are <back>
based on generic SDP offer/answer negotiation rules for SCTP <references pn="section-10">
based media transport as specified in <xref target="I-D.ietf-mmusic-sctp-sd <name slugifiedName="name-references">References</name>
p"/> for <references pn="section-10.1">
the SDP "m" line proto values UDP/DTLS/SCTP and TCP/DTLS/SCTP. <name slugifiedName="name-normative-references">Normative References</na
In the future, data channels could be defined over other SCTP based protoco me>
ls, such as <reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2
SCTP over IP. However, corresponding potential other "m" line proto values 119" quoteTitle="true" derivedAnchor="RFC2119">
are not <front>
considered in this document." <title>Key words for use in RFCs to Indicate Requirement Levels</tit
</t> le>
</list> <author initials="S." surname="Bradner" fullname="S. Bradner">
</t> <organization showOnFrontPage="true"/>
<t>Replacement of "DTLS connectio </author>
n" with "DTLS association" throughout the document. <date year="1997" month="March"/>
</t> <abstract>
<t>In sections <xref target="dcma <t indent="0">In many standards track documents several words are
p-mux-category"/> and used to signify the requirements in the specification. These words are often ca
<xref target="dcsa-mux-category"/> removal of the sentences "This document al pitalized. This document defines these words as they should be interpreted in IE
so TF documents. This document specifies an Internet Best Current Practices for th
does not specify multiplexing rules for this attribute for SCTP or e Internet Community, and requests discussion and suggestions for improvements.<
SCTP/DTLS proto values". /t>
</t> </abstract>
<t>In the text related to "Subseq </front>
uent SDP answer" in section <seriesInfo name="BCP" value="14"/>
<xref target="various_SDP_OA_considerations"/> replacement of "The DTLS/SCTP <seriesInfo name="RFC" value="2119"/>
association remains open ..." with "The SCTP association remains open ...". <seriesInfo name="DOI" value="10.17487/RFC2119"/>
</t> </reference>
<t>In the text after the second S <reference anchor="RFC3264" target="https://www.rfc-editor.org/info/rfc3
DP answer in section 264" quoteTitle="true" derivedAnchor="RFC3264">
<xref target="examples"/> replacement of "... (after SCTP/DTLS association is <front>
setup)" <title>An Offer/Answer Model with Session Description Protocol (SDP)
with "... (after the SCTP association is set up)". </title>
</t> <author initials="J." surname="Rosenberg" fullname="J. Rosenberg">
<t>Addition of draft-ietf-mmusic- <organization showOnFrontPage="true"/>
dtls-sdp to the list of informative </author>
references. <author initials="H." surname="Schulzrinne" fullname="H. Schulzrinne
</t> ">
<t>Addition of "a=dtls-id" attrib <organization showOnFrontPage="true"/>
ute lines to the SDP offer/answer examples in </author>
<xref target="examples"/>. <date year="2002" month="June"/>
</t> <abstract>
</list> <t indent="0">This document defines a mechanism by which two entit
</t> ies can make use of the Session Description Protocol (SDP) to arrive at a common
</section> view of a multimedia session between them. In the model, one participant offer
<section title="Changes against 'draft-ietf-mmusic-data-c s the other a description of the desired session from their perspective, and the
hannel-sdpneg-08'"> other participant answers with the desired session from their perspective. Thi
<t> s offer/answer model is most useful in unicast sessions where information from b
<list style="symbols"> oth participants is needed for the complete view of the session. The offer/answ
<t>Addition of definition of "dat er model is used by protocols like the Session Initiation Protocol (SIP). [STAN
a channel subprotocol" to DARDS-TRACK]</t>
<xref target="terminology"/> as proposed on the MMUSIC list, </abstract>
https://www.ietf.org/mail-archive/web/mmusic/current/msg15827.html. </front>
</t> <seriesInfo name="RFC" value="3264"/>
<t>Addition of RFC4566bis draft <seriesInfo name="DOI" value="10.17487/RFC3264"/>
to list of normative references. </reference>
</t> <reference anchor="RFC3629" target="https://www.rfc-editor.org/info/rfc3
<t>Updates of tables in <xref tar 629" quoteTitle="true" derivedAnchor="RFC3629">
get="IANA-reg-dcmap"/> and <front>
<xref target="IANA-reg-dcsa"/> as per section 8.2.4 <title>UTF-8, a transformation format of ISO 10646</title>
of RFC4566bis draft. <author initials="F." surname="Yergeau" fullname="F. Yergeau">
</t> <organization showOnFrontPage="true"/>
<t>Addition of new "new-usage-lev </author>
el">. <date year="2003" month="November"/>
</t> <abstract>
</list> <t indent="0">ISO/IEC 10646-1 defines a large character set called
</t> the Universal Character Set (UCS) which encompasses most of the world's writing
</section> systems. The originally proposed encodings of the UCS, however, were not compa
<section title="Changes against 'draft-ietf-mmusic-data-c tible with many current applications and protocols, and this has led to the deve
hannel-sdpneg-07'"> lopment of UTF-8, the object of this memo. UTF-8 has the characteristic of pres
<t> erving the full US-ASCII range, providing compatibility with file systems, parse
<list style="symbols"> rs and other software that rely on US-ASCII values but are transparent to other
<t>Addition of two new paragraphs values. This memo obsoletes and replaces RFC 2279.</t>
to <xref target="dcsa-attribute"/> regarding </abstract>
subprotocol attribute relationship with transport protocol. </front>
</t> <seriesInfo name="STD" value="63"/>
<t>Addition of a note to <xref ta <seriesInfo name="RFC" value="3629"/>
rget="IANA_subproto_ids"/> regarding subprotocols <seriesInfo name="DOI" value="10.17487/RFC3629"/>
simultaneously defined for data channel and Websocket usage. </reference>
</t> <reference anchor="RFC4960" target="https://www.rfc-editor.org/info/rfc4
<t>Addition of two further SDP of 960" quoteTitle="true" derivedAnchor="RFC4960">
fer/answer considerations to <front>
<xref target="various_SDP_OA_considerations"/> regarding unknown subprotocol <title>Stream Control Transmission Protocol</title>
attributes and known subprotocol attributes with unknown data channel transp <author initials="R." surname="Stewart" fullname="R. Stewart" role="
ort editor">
related semantic. <organization showOnFrontPage="true"/>
</t> </author>
</list> <date year="2007" month="September"/>
</t> <abstract>
</section> <t indent="0">This document obsoletes RFC 2960 and RFC 3309. It d
<section title="Changes against 'draft-ietf-mmusic-data-c escribes the Stream Control Transmission Protocol (SCTP). SCTP is designed to t
hannel-sdpneg-06'"> ransport Public Switched Telephone Network (PSTN) signaling messages over IP net
<t> works, but is capable of broader applications.</t>
<list style="symbols"> <t indent="0">SCTP is a reliable transport protocol operating on t
<t>Changes addressing Christian G op of a connectionless packet network such as IP. It offers the following servi
roves's WGLC review comments raised in ces to its users:</t>
http://www.ietf.org/mail-archive/web/mmusic/current/msg15357.html and <t indent="0">-- acknowledged error-free non-duplicated transfer
http://www.ietf.org/mail-archive/web/mmusic/current/msg15359.html. of user data,</t>
</t> <t indent="0">-- data fragmentation to conform to discovered path
</list> MTU size,</t>
</t> <t indent="0">-- sequenced delivery of user messages within multi
</section> ple streams, with an option for order-of-arrival delivery of individual user mes
<section title="Changes against 'draft-ietf-mmusic-data-c sages,</t>
hannel-sdpneg-05'"> <t indent="0">-- optional bundling of multiple user messages into
<t> a single SCTP packet, and</t>
<list style="symbols"> <t indent="0">-- network-level fault tolerance through supporting
<t>In IANA registration <xref tar of multi-homing at either or both ends of an association.</t>
get="IANA-reg-dcmap"/> and <t indent="0"> The design of SCTP includes appropriate congestion
<xref target="IANA-reg-dcsa"/> replacement of contact name and e-mail address avoidance behavior and resistance to flooding and masquerade attacks. [STANDARD
with "MMUSIC Chairs" and "mmusic-chairs@ietf.org". S-TRACK]</t>
</t> </abstract>
<t>In <xref target="dcsa-attribut </front>
e"/> replacement of "Thus in the example above, the <seriesInfo name="RFC" value="4960"/>
original attribute line "a=accept- <seriesInfo name="DOI" value="10.17487/RFC4960"/>
types:text/plain" is represented by the attribute line "a=dcsa:2 </reference>
accept-types:text/plain", which specifies that this instance of MSRP <reference anchor="RFC5234" target="https://www.rfc-editor.org/info/rfc5
being transported on the SCTP association using the data channel with 234" quoteTitle="true" derivedAnchor="RFC5234">
stream id 2 accepts plain text files." with "... which specifies that this <front>
instance of the MSRP subprotocol being transported ...". <title>Augmented BNF for Syntax Specifications: ABNF</title>
</t> <author initials="D." surname="Crocker" fullname="D. Crocker" role="
<t>The last paragraph of <xref ta editor">
rget="dcsa-attribute"/> started with <organization showOnFrontPage="true"/>
"Note: This document does not provide a complete specification ...". </author>
Removal of "Note:" and move of this paragraph to the introduction in <author initials="P." surname="Overell" fullname="P. Overell">
<xref target="introduction"/> as last paragraph. <organization showOnFrontPage="true"/>
</t> </author>
<t> <date year="2008" month="January"/>
<xref target="prot_att"/> <abstract>
's headline was "Subprotocol Specific Attributes". <t indent="0">Internet technical specifications often need to defi
Change of this headline to "Other Media Level Attributes" and adaptations of ne a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF
the first ), called Augmented BNF (ABNF), has been popular among many Internet specificati
paragraph of this section and the first paragraph of <xref target="dcsa-attri ons. The current specification documents ABNF. It balances compactness and simp
bute"/> licity with reasonable representational power. The differences between standard
in order to clarify that not only those attributes may be BNF and ABNF involve naming rules, repetition, alternatives, order-independence
encapsulated in a "dcsa" attribute, which are specifically defined for the , and value ranges. This specification also supplies additional rule definition
subprotocol, but that also other attributes may be encapsulated if s and encoding for a core lexical analyzer of the type common to several Interne
they are related to the specific subprotocol instance. t specifications. [STANDARDS-TRACK]</t>
</t> </abstract>
<t>Move of the last but one parag </front>
raph of <xref target="dcsa-attribute"/> starting with <seriesInfo name="STD" value="68"/>
"The same syntax applies to ..." right in front of the formal syntax definiti <seriesInfo name="RFC" value="5234"/>
on of the <seriesInfo name="DOI" value="10.17487/RFC5234"/>
"dcsa" attribute. </reference>
</t> <reference anchor="RFC6525" target="https://www.rfc-editor.org/info/rfc6
<t>Modifications of the text in < 525" quoteTitle="true" derivedAnchor="RFC6525">
xref target="dcmap-mux-category"/> and <front>
<xref target="dcsa-mux-category"/> in order not to explicitly restrict usage <title>Stream Control Transmission Protocol (SCTP) Stream Reconfigur
of the ation</title>
"a=dcmap:" and "a=dcsa:" attributes to "m" lines with proto values "UDP/DTLS/ <author initials="R." surname="Stewart" fullname="R. Stewart">
SCTP" <organization showOnFrontPage="true"/>
or "TCP/DTLS/SCTP". </author>
</t> <author initials="M." surname="Tuexen" fullname="M. Tuexen">
</list> <organization showOnFrontPage="true"/>
</t> </author>
</section> <author initials="P." surname="Lei" fullname="P. Lei">
<section title="Changes against 'draft-ietf-mmusic-data-c <organization showOnFrontPage="true"/>
hannel-sdpneg-04'"> </author>
<t> <date year="2012" month="February"/>
<list style="symbols"> <abstract>
<t>In <xref target="subprotocol-p <t indent="0">Many applications that use the Stream Control Transm
arameter"/> the first (and only) paragraph was ission Protocol (SCTP) want the ability to "reset" a stream. The intention of r
"The 'subprotocol' parameter indicates which protocol the esetting a stream is to set the numbering sequence of the stream back to 'zero'
client expects to exchange via the channel. with a corresponding notification to the application layer that the reset has be
'subprotocol' is an optional parameter. en performed. Applications requiring this feature want it so that they can "reu
If the 'subprotocol' parameter is not present, then its value se" streams for different purposes but still utilize the stream sequence number
defaults to the empty string." so that the application can track the message flows. Thus, without this feature
Replacement of this paragraph with following two paragraphs: , a new use of an old stream would result in message numbers greater than expect
<list style="symbols"> ed, unless there is a protocol mechanism to "reset the streams back to zero". T
<t> The 'subproto his document also includes methods for resetting the transmission sequence numbe
col' parameter indicates which protocol the rs, adding additional streams, and resetting all stream sequence numbers. [STAN
client expects to exchange via the channel. DARDS-TRACK]</t>
This parameter maps to the 'Protocol' parameter defined in </abstract>
<xref target="I-D.ietf-rtcweb-data-protocol"/>. </front>
<xref target="IANA_subproto_ids"/> specifies how new subprotocol parameter <seriesInfo name="RFC" value="6525"/>
values are registered. <seriesInfo name="DOI" value="10.17487/RFC6525"/>
'subprotocol' is an optional parameter. </reference>
If the 'subprotocol' parameter is not present, then its value <reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
defaults to the empty string. 174" quoteTitle="true" derivedAnchor="RFC8174">
</t> <front>
<t>Note: The empt <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
y string MAY also be explicitly used as 'subprotocol' value, tle>
such that 'subprotocol=""' is equivalent to the 'subprotocol' parameter no <author initials="B." surname="Leiba" fullname="B. Leiba">
t being <organization showOnFrontPage="true"/>
present at all. <xref target="I-D.ietf-rtcweb-data-protocol"/> allows the </author>
DATA_CHANNEL_OPEN message's 'subprotocol' value to be an empty string. <date year="2017" month="May"/>
</t> <abstract>
</list> <t indent="0">RFC 2119 specifies common key words that may be used
</t> in protocol specifications. This document aims to reduce the ambiguity by cla
<t>Addition of <xref target="I-D. rifying that only UPPERCASE usage of the key words have the defined special mea
ietf-mmusic-sdp-mux-attributes"/> nings.</t>
to list the of normative references. </abstract>
</t> </front>
<t>Addition of dcmap attribute sp <seriesInfo name="BCP" value="14"/>
ecific IANA registration <seriesInfo name="RFC" value="8174"/>
<xref target="IANA-reg-dcmap"/>. <seriesInfo name="DOI" value="10.17487/RFC8174"/>
</t> </reference>
<t>Addition of dcsa attribute spe <reference anchor="RFC8831" target="https://www.rfc-editor.org/info/rfc8
cific IANA registration 831" quoteTitle="true" derivedAnchor="RFC8831">
<xref target="IANA-reg-dcsa"/>. <front>
</t> <title>WebRTC Data Channels</title>
<t>Addition of new <xref target=" <author initials="R" surname="Jesup" fullname="Randell Jesup">
dcmap-mux-category"/> describing the mux category <organization showOnFrontPage="true"/>
of the dcmap SDP attribute. This section and the new "a=dcsa:" attribute rel </author>
ated <author initials="S" surname="Loreto" fullname="Salvatore Loreto">
mux category section are similar to the "Mux Category" sections of <organization showOnFrontPage="true"/>
the "a=sctp-port:" and "a=max-message-size:" attributes in </author>
<xref target="I-D.ietf-mmusic-sctp-sdp"/>. <author initials="M" surname="Tüxen" fullname="Michael Tüxen">
</t> <organization showOnFrontPage="true"/>
<t>Addition of new <xref target=" </author>
dcsa-mux-category"/> describing the mux category <date month="January" year="2021"/>
of the dcsa SDP attribute. </front>
</t> <seriesInfo name="RFC" value="8831"/>
</list> <seriesInfo name="DOI" value="10.17487/RFC8831"/>
</t> </reference>
</section> <reference anchor="RFC8832" target="https://www.rfc-editor.org/info/rfc8
<section title="Changes against 'draft-ietf-mmusic-data-c 832" quoteTitle="true" derivedAnchor="RFC8832">
hannel-sdpneg-03'"> <front>
<t> <title>WebRTC Data Channel Establishment Protocol</title>
<list style="symbols"> <author initials="R." surname="Jesup" fullname="Randell Jesup">
<t>In <xref target="introduction" <organization showOnFrontPage="true"/>
/> replacement of </author>
"RTCWeb leaves it open for other applications to use data channels and its in <author initials="S." surname="Loreto" fullname="Salvatore Loreto">
-band <organization showOnFrontPage="true"/>
DCEP or out-of-band non-DCEP protocols for creating them" with </author>
"... to use data channels and its in-band DCEP or other in-band or out-of-ban <author initials="M" surname="Tüxen" fullname="Michael Tüxen">
d <organization showOnFrontPage="true"/>
protocols for creating them". </author>
Additionally replacement of <date month="January" year="2021"/>
"In particular, the SDP offer generated by the application </front>
includes no channel-specific information" with <seriesInfo name="RFC" value="8832"/>
"... generated by the RTCweb data channel stack includes <seriesInfo name="DOI" value="10.17487/RFC8832"/>
no channel-specific information". </reference>
</t> <reference anchor="RFC8841" target="https://www.rfc-editor.org/info/rfc8
<t>Move of former section 5 ("Dat 841" quoteTitle="true" derivedAnchor="RFC8841">
a Channels") to new <front>
<xref target="generic-out-of-band-aspects"/> and removal of JavaScript API sp <title>Session Description Protocol (SDP) Offer/Answer Procedures fo
ecific r Stream Control Transmission Protocol (SCTP) over Datagram Transport Layer Secu
discussions from this moved text (like mentioning of data channel stack speci rity (DTLS) Transport</title>
fic <author initials="C." surname="Holmberg" fullname="Christer Holmberg
states). Therefore former section 6 ("SDP Offer/Answer Negotiation") is now ">
<xref target="sdp_synt"/>. <organization showOnFrontPage="true"/>
</t> </author>
<t>In <xref target="sdp_synt"/>: <author initials="R." surname="Shpount" fullname="Roman Shpount">
<list style="symbols"> <organization showOnFrontPage="true"/>
<t>Relacement of </author>
<xref target="sdp_synt"/>'s <author initials="S." surname="Loreto" fullname="Salvatore Loreto">
first paragraph <organization showOnFrontPage="true"/>
"This section defines a method of non-DCEP negotiation by which two </author>
clients can negotiate data channel-specific and subprotocol-specific <author initials="G." surname="Camarillo" fullname="Gonzalo Camarill
parameters, using the out-of-band SDP offer/answer exchange. This o">
SDP extension can only be used with the SDP offer/answer model." with <organization showOnFrontPage="true"/>
"This section defines an SDP extension by which </author>
two clients can negotiate data channel-specific and subprotocol-specific <date month="January" year="2021"/>
parameters without using DCEP <xref target="I-D.ietf-rtcweb-data-protocol"/ </front>
>. <seriesInfo name="RFC" value="8841"/>
This SDP extension only defines usage in the context of SDP offer/answer." <seriesInfo name="DOI" value="10.17487/RFC8841"/>
</t> </reference>
<t>Addition of ne <reference anchor="RFC8859" target="https://www.rfc-editor.org/info/rfc8
w paragraph: 859" quoteTitle="true" derivedAnchor="RFC8859">
"<xref target="generic-out-of-band-aspects"/> provides information how data <front>
channels <title>A Framework for Session Description Protocol (SDP) Attributes
work in general and especially summarizes some key aspects, which should be When Multiplexing</title>
considered for the negotiation of data channels if DCEP is not used." <author initials="S" surname="Nandakumar" fullname="Suhas Nandakumar
</t> ">
</list> <organization showOnFrontPage="true"/>
</t> </author>
<t>In <xref target="subsec-sdp-at <date month="January" year="2021"/>
tr-for-dc-par-neg"/> replacement of "The intention of </front>
exchanging these attributes is to create data channels on both the peers with <seriesInfo name="RFC" value="8859"/>
the same <seriesInfo name="DOI" value="10.17487/RFC8859"/>
set of attributes without actually using the DCEP </reference>
<xref target="I-D.ietf-rtcweb-data-protocol"/>" with "The intention in exchan <reference anchor="RFC8866" target="https://www.rfc-editor.org/info/rfc8
ging 866" quoteTitle="true" derivedAnchor="RFC8866">
these attributes is to create, on two peers, without use of DCEP <front>
<xref target="I-D.ietf-rtcweb-data-protocol"/>, <title>SDP: Session Description Protocol</title>
matched pairs of oppositely directed data channels having the same set of att <author initials="A" surname="Begen" fullname="Ali Begen">
ributes". <organization showOnFrontPage="true"/>
</t> </author>
<t>In <xref target="max-retr-para <author initials="P" surname="Kyzivat" fullname="Paul Kyzivat">
m-definition"/> replacement of "The 'max-retr' <organization showOnFrontPage="true"/>
parameter indicates the maximal number a user message will be retransmitted" </author>
with "The <author initials="C" surname="Perkins" fullname="Colin Perkins">
'max-retr' parameter indicates the maximal number of times a user message wil <organization showOnFrontPage="true"/>
l </author>
be retransmitted". <author initials="M" surname="Handley" fullname="Mark Handley">
</t> <organization showOnFrontPage="true"/>
<t>In <xref target="id_mngt"/> re </author>
placement of "However, an SDP offer/answer exchange <date month="January" year="2021"/>
MUST NOT be initiated if the associated SCTP stream is already negotiated via </front>
DCEP" <seriesInfo name="RFC" value="8866"/>
with "However, an SCTP stream MUST NOT be referenced in a dcmap or dcsa <seriesInfo name="DOI" value="10.17487/RFC8866"/>
attribute of an SDP offer/answer exchange if the associated SCTP stream has a </reference>
lready </references>
been negotiated via DCEP". <references pn="section-10.2">
</t> <name slugifiedName="name-informative-references">Informative References
<t>In the examples in <xref targe </name>
t="examples"/> addition of the previously missing <reference anchor="RFC4975" target="https://www.rfc-editor.org/info/rfc4
colons to the "a=sctp-port" attribute lines. 975" quoteTitle="true" derivedAnchor="RFC4975">
</t> <front>
</list> <title>The Message Session Relay Protocol (MSRP)</title>
</t> <author initials="B." surname="Campbell" fullname="B. Campbell" role
</section> ="editor">
<section title="Changes against 'draft-ietf-mmusic-data-c <organization showOnFrontPage="true"/>
hannel-sdpneg-02'"> </author>
<t> <author initials="R." surname="Mahy" fullname="R. Mahy" role="editor
<list style="symbols"> ">
<t>Move of reference draft-ietf-r <organization showOnFrontPage="true"/>
tcweb-jsep from the list of normative </author>
references to the list of informative references. Remover in -07 since not ref <author initials="C." surname="Jennings" fullname="C. Jennings" role
erenced</t> ="editor">
<t>Addition of IANA SDP parameter <organization showOnFrontPage="true"/>
s to the list of informative </author>
references <date year="2007" month="September"/>
and addition of following two sentences to the first paragraph after the ABNF <abstract>
definition: "Note however that not all SDP attributes are suitable <t indent="0">This document describes the Message Session Relay Pr
as "a=dcsa:" parameter. IANA SDP parameters contains otocol, a protocol for transmitting a series of related instant messages in the
the lists of IANA registered session and media level or context of a session. Message sessions are treated like any other media stream
media level only SDP attributes."</t> when set up via a rendezvous or session creation protocol such as the Session In
<t>In the introduction replacemen itiation Protocol. [STANDARDS-TRACK]</t>
t of last sentence </abstract>
"This document defines SDP-based out-of-band negotiation procedures </front>
to establish data channels for transport of well-defined subprotocols" <seriesInfo name="RFC" value="4975"/>
with <seriesInfo name="DOI" value="10.17487/RFC4975"/>
"This document defines SDP offer/answer negotiation procedures </reference>
to establish data channels for transport of well-defined subprotocols, <reference anchor="RFC6455" target="https://www.rfc-editor.org/info/rfc6
to enable out-of-band negotiation". 455" quoteTitle="true" derivedAnchor="RFC6455">
</t> <front>
<t>Throughout the document replac <title>The WebSocket Protocol</title>
ement of "external negotiation" with <author initials="I." surname="Fette" fullname="I. Fette">
"SDP offer/answer negotiation" and removal of term "external negotiation" from <organization showOnFrontPage="true"/>
the </author>
terminology list in <xref target="terminology"/>.</t> <author initials="A." surname="Melnikov" fullname="A. Melnikov">
<t> Throughout the document repla <organization showOnFrontPage="true"/>
cement of "internal negotiation" with </author>
"DCEP" and removal of terms "internal negotiation" and "in-band negotiation" <date year="2011" month="December"/>
from the terminology list in <xref target="terminology"/>.</t> <abstract>
<t>Addition of "SCTP Stream Seque <t indent="0">The WebSocket Protocol enables two-way communication
nce Number (SSN)" to the list of terms.</t> between a client running untrusted code in a controlled environment to a remote
<t>In <xref target="id_mngt"/> re host that has opted-in to communications from that code. The security model us
placement of sentence ed for this is the origin-based security model commonly used by web browsers. T
"However, a single stream is managed using one method at a time." with he protocol consists of an opening handshake followed by basic message framing,
"However, an SDP offer/answer exchange MUST NOT be initiated layered over TCP. The goal of this technology is to provide a mechanism for bro
if the associated SCTP stream is already negotiated via DCEP".</t> wser-based applications that need two-way communication with servers that does n
<t>In <xref target="param_negotia ot rely on opening multiple HTTP connections (e.g., using XMLHttpRequest or &lt;
tion"/> replacement of sentence iframe&gt;s and long polling). [STANDARDS-TRACK]</t>
"By definition max-retr and max-time are mutually exclusive, so only one of </abstract>
them can be present in a=dcmap" with </front>
"By definition max-retr and max-time are mutually exclusive, <seriesInfo name="RFC" value="6455"/>
so aBoth MUST NOT be present in a=dcmap".</t> <seriesInfo name="DOI" value="10.17487/RFC6455"/>
<t>Move of reference <xref target </reference>
="WebRtcAPI"/> from list of normative references <reference anchor="RFC8850" target="https://www.rfc-editor.org/info/rfc8
to list of informative references.</t> 850" quoteTitle="true" derivedAnchor="RFC8850">
<t>Removal of almost all text par <front>
ts, which discussed JavaScript or other API specific <title>Controlling Multiple Streams for Telepresence (CLUE) Protocol
aspects. Such API specific aspects were mainly discussed in sub-sections of Se Data Channel</title>
ction 5 <author initials="C." surname="Holmberg" fullname="Christer Holmberg
and <xref target="sdp_synt"/> ">
of draft-ietf-mmusic-data-channel-sdpneg-02.</t> <organization showOnFrontPage="true"/>
</list> </author>
</t> <date month="January" year="2021"/>
</section> </front>
<section title="Changes against 'draft-ietf-mmusic-data-c <seriesInfo name="RFC" value="8850"/>
hannel-sdpneg-01'"> <seriesInfo name="DOI" value="10.17487/RFC8850"/>
<t> </reference>
<list style="symbols"> <reference anchor="RFC8855" target="https://www.rfc-editor.org/info/rfc8
<t>New <xref target="appl_stateme 855" quoteTitle="true" derivedAnchor="RFC8855">
nt"/> regarding applicability to <front>
SDP offer/answer only.</t> <title>The Binary Floor Control Protocol (BFCP)</title>
<t>Addition of new <xref target=" <author initials="G." surname="Camarillo" fullname="Gonzalo Camarill
IANA_subproto_ids"/> "Subprotocol identifiers" as o">
subsection of the "IANA Considerations" related <xref target="IANA"/>. <organization showOnFrontPage="true"/>
Also removal of the temporary note </author>
"To be completed. As [I-D.ietf-rtcweb-data-protocol] this document should re <author initials="K." surname="Drage" fullname="Keith Drage">
fer to <organization showOnFrontPage="true"/>
IANA's WebSocket Subprotocol Name Registry defined in <xref target="RFC6455"/ </author>
>"</t> <author initials="T." surname="Kristensen" fullname="Tom Kristensen"
<t> In <xref target="param_negoti >
ation"/>: <organization showOnFrontPage="true"/>
<list style="symbols"> </author>
<t>In the first p <author initials="J." surname="Ott" fullname="Jörg Ott">
aragraph <organization showOnFrontPage="true"/>
replacement of the sentence "If an SDP offer </author>
contains both of these parameters then such an SDP offer will be rejected." <author initials="C." surname="Eckel" fullname="Charles Eckel">
with "If <organization showOnFrontPage="true"/>
an SDP offer contains both of these parameters then the receiver of such an </author>
SDP <date month="January" year="2021"/>
offer MUST reject the SDP offer." </t> </front>
<t>In the second <seriesInfo name="RFC" value="8855"/>
paragraph <seriesInfo name="DOI" value="10.17487/RFC8855"/>
capitalization of "shall" and "may" such that both sentences now read: </reference>
"The SDP answer SHALL echo the same subprotocol, max-retr, max-time, <reference anchor="RFC8873" target="https://www.rfc-editor.org/info/rfc8
ordered parameters, if those were present in the offer, and MAY include 873" quoteTitle="true" derivedAnchor="RFC8873">
a label parameter. They MAY appear in any order, which could be <front>
different from the SDP offer, in the SDP answer."</t> <title>Message Session Relay Protocol (MSRP) over Data Channels</tit
<t>In the third p le>
aragraph <author initials="JM." surname="Recio" fullname="Jose Recio" role="e
replacement of the sentence ditor">
"The same information MUST be replicated without changes in any subsequent <organization showOnFrontPage="true"/>
offer or </author>
answer, as long as the data channel is still opened at the time of offer or <author initials="C" surname="Holmberg" fullname="Christer Holmberg"
answer >
generation." with <organization showOnFrontPage="true"/>
"When sending a subsequent offer or an answer, and for as long as the data </author>
channel <date month="January" year="2021"/>
is still open, the sender MUST replicate the same information.".</t> </front>
</list> <seriesInfo name="RFC" value="8873"/>
</t> <seriesInfo name="DOI" value="10.17487/RFC8873"/>
<t>In <xref target="param_negotia </reference>
tion"/> the mapping of data channel types defined in <reference anchor="T38" target="https://www.itu.int/rec/T-REC-T.38-20151
<xref target="I-D.ietf-rtcweb-data-protocol"/> to the SDP "a=dcmap" attribute 1-I/en" quoteTitle="true" derivedAnchor="T38">
parameters were illustrated using example "a=dcmap" attribute lines. <front>
Replacement of these example "a=dcmap" attribute lines with just the "a=dcmap <title>Procedures for real-time Group 3 facsimile communication over
" IP networks</title>
attribute parameters being relevant for the channel type.</t> <author>
<t>In <xref target="various_SDP_O <organization showOnFrontPage="true">International Telecommunicati
A_considerations"/> the description of bullet on Union</organization>
point "SDP offer has no a=dcmap attributes - Initial SDP offer:" was </author>
"Initial SDP offer: No data channel negotiated yet." <date month="November" year="2015"/>
Replacement of this description with </front>
"Initial SDP offer: No data channel is negotiated yet. <seriesInfo name="ITU-T Recommendation" value="T.38"/>
The DTLS connection and SCTP association is </reference>
negotiated and, if agreed, established as per <reference anchor="WebRtcAPI" target="https://www.w3.org/TR/webrtc/" quo
<xref target="I-D.ietf-mmusic-sctp-sdp"/>."</t> teTitle="true" derivedAnchor="WebRtcAPI">
<t>In <xref target="various_SDP_O <front>
A_considerations"/> in both bullet points related to <title>WebRTC 1.0: Real-time Communication Between Browsers</title>
"Subsequent SDP offer" and "Subsequent SDP answer" replacement of <author initials="C." surname="Jennings" fullname="Cullen Jennings">
"All the externally negotiated data channels must be closed now." with <organization showOnFrontPage="true"/>
"All the externally negotiated data channels are expected to be closed now.". </author>
</t> <author initials="H." surname="Boström" fullname="Henrik Boström">
<t>In <xref target="ext_open"/>'s <organization showOnFrontPage="true"/>
sixth paragraph </author>
replacement of the two occurrences of "must" with "MUST".</t> <author initials="J-I." surname="Bruaroey" fullname="Jan-Ivar Bruaro
<t>In <xref target="dcmap-attr-de ey">
finition"/> in the definition of the ABNF rule <organization showOnFrontPage="true"/>
"dcmap-opt" there was a comment saying that </author>
"Only maxretr-opt or maxtime-opt is present. Both MUST NOT be present." <date/>
Removal of the second normative sentence and instead addition of following ne </front>
w <refcontent>W3C Proposed Recommendation</refcontent>
paragraph to the end of this section: </reference>
"Within an 'a=dcmap' attribute line's 'dcmap-opt' value only one </references>
'maxretr-opt' parameter or one 'maxtime-opt' parameter is present. </references>
Both MUST NOT be present."</t> <section anchor="generic-out-of-band-aspects" numbered="true" removeInRFC="f
<t>In <xref target="ordered-param alse" toc="include" pn="section-appendix.a">
-description"/> replacement of the first sentence <name slugifiedName="name-generic-data-channel-negoti">Generic Data Channe
"The 'ordered' parameter with value "true" indicates that DATA chunks in the l Negotiation Aspects when Not Using DCEP</name>
channel <t indent="0" pn="section-appendix.a-1">This appendix summarizes how data
MUST be dispatched to the upper layer by the receiver while preserving the or channels work in general and discusses
der." some key aspects that should be considered for the out-of-band negotiation of
with data
"The 'ordered' parameter with value "true" indicates that the receiver MUST d
ispatch
DATA chunks in the data channel to the upper layer while preserving the order
.".</t>
<t>In <xref target="opendc"/>'s f
irst paragraph replacement of the one occurrence of
"must" with "..., it MUST wait until ...".</t>
<t>In <xref target="close-dc"/>:
<list style="symbols">
<t>In the second
paragraph replacement of "must" with "... whether this closing MUST
in addition ..."</t>
<t>In the third p
aragraph replacement of the sentence
"The port value for the "m" line SHOULD NOT be changed (e.g., to zero)
when closing a data channel ..." with
"The offerer SHOULD NOT change the port value for the "m" line (e.g., to ze
ro) when
closing a data channel ...".</t>
<t>In the last bu
t two paragraph replacement of the sentence
"... then an SDP offer which excludes this closed data channel SHOULD be ge
nerated."
with
"... then the client SHOULD generate an SDP offer which excludes this close
d data
channel.".</t>
<t>In the last bu
t one paragraph replacement of "must" with
"The application MUST also close...".</t>
</list>
</t>
<t>In <xref target="prot_att"/> a
ddition of following note after the formal definition
of the 'a=dcsa' attribute:
"Note that the above reference to RFC 4566 defines were the
attribute definition can be found;
it does not provide any limitation on support of attributes
defined in other documents in accordance with this attribute
definition."</t>
</list>
</t>
</section>
<section title="Changes against 'draft-ietf-mmusic-data-c
hannel-sdpneg-00'">
<t>
<list style="symbols">
<t>In <xref target="terminology"/
> "WebRTC data channel" was defined as
"A bidirectional channel consisting of paired
SCTP outbound and inbound streams."
Replacement of this definition with
"Data channel: A WebRTC data channel as specified in
<xref target="I-D.ietf-rtcweb-data-channel"/>", and consistent usage
of "data channel" in the remainder of the document including the
document's headline."</t>
<t>In Section 5 removal of follow
ing note:
'OPEN ISSUE: The syntax in <xref target="I-D.ietf-mmusic-sctp-sdp"/> may
change as that document progresses. In particular we expect
"webrtc-datachannel" to become a more general term.'</t>
<t>Consistent usage of '"m" line'
in whole document as per RFC4566.</t>
<t>In <xref target="subsec-sdp-at
tr-for-dc-par-neg"/>
removal of the example dcmap attribute line
'a=dcmap:2 subprotocol="bfcp";label="channel 2' as there are already
four examples right after the ABNF rules in
<xref target="dcmap-attr-definition"/>.
Corresponding removal of following related note:
"Note: This document does not provide a complete specification
of how to negotiate the use of a WebRTC data channel to transport BFCP.
Procedures specific to each subprotocol such as BFCP will be
documented elsewhere. The use of BFCP is only an example of how
the generic procedures described herein might apply to a specific
subprotocol."</t>
<t>In <xref target="subsec-sdp-at
tr-for-dc-par-neg"/>
removal of following note:
"Note: This attribute is derived from attribute "webrtc-DataChannel",
which was defined in old version 03 of the
following draft, but which was removed along with any support for SDP
external negotiation in subsequent versions:
<xref target="I-D.ietf-mmusic-sctp-sdp"/>."</t>
<t>Insertion of following new sen
tence to the beginning of
<xref target="dcmap-attr-definition"/>:
"dcmap is a media level attribute having following ABNF syntax:"</t>
<t>Insertion of new <xref target=
"dcmap-stream-id-param-definition"/>
containing the dcmap-stream-id specifying sentence, which previously
was placed right before the formal ABNF rules.
Removal of the sentence 'Stream is a mandatory
parameter and is noted directly after the "a=dcmap:" attribute's
colon' as this information is part of the ABNF specification.</t>
<t>In <xref target="dcmap-attr-de
finition"/> modification of the
'ordering-value' values from "0" or "1" to "true" or "false".
Corresponding text modifications in <xref target="ordered-param-description"/
>.</t>
<t>In <xref target="dcmap-attr-de
finition"/> the ABNF definition of "quoted-string"
referred to rule name "escaped-char", which was not defined.
Instead a rule with name "escaped" was defined. Renamed that rule's name
to "escaped-char".</t>
<t>Insertion of a dedicated note
right after the "a=dcmap:4" attribute example
in <xref target="dcmap-attr-definition"/> regarding the non-printable
"escaped-char" character within the "label" value.</t>
<t>In <xref target="prot_att"/>'s
second paragraph replacement of
"sctp stream identifier" with "SCTP stream identifier".</t>
<t>In first paragraph of <xref ta
rget="id_mngt"/> replacement of first two sentences
'For the SDP-based external negotiation described in this document,
the initial offerer based "SCTP over DTLS" owns by convention the
even stream identifiers whereas the initial answerer owns the odd stream
identifiers. This ownership is invariant for the whole
lifetime of the signaling session, e.g. it does not change if the
initial answerer sends a new offer to the initial offerer.'
with
'If an SDP offer/answer exchange
(could be the initial or a subsequent one)
results in a UDP/DTLS/SCTP or TCP/DTLS/SCTP based media description being
accepted, and if this SDP offer/answer exchange results in the
establishment of a new SCTP association, then the SDP offerer owns the
even SCTP stream ids of this new SCTP association and the answerer owns
the odd SCTP stream identifiers.
If this "m" line is removed from the signaling session (its port number
set to zero), and if usage of this or of a new UDP/DTLS/SCTP or
TCP/DTLS/SCTP based "m" line is renegotiated later on,
then the even and odd SCTP stream identifier
ownership is redetermined as well as described above.'</t>
<t>In <xref target="opendc"/> the
first action of an SDP answerer,
when receiving an SDP offer, was described as
"Applies the SDP offer. Note that the browser ignores data channel
specific attributes in the SDP."
Replacement of these two sentences with
"Parses and applies the SDP offer. Note that the typical parser
normally ignores unknown SDP attributes, which includes data
channel related attributes."</t>
<t>In <xref target="opendc"/> the
second sentence of the third
SDP answerer action was
"Note that the browser is asked to create data
channels with stream identifiers not "owned" by the agent.".
Replacement of this sentence with
"Note that the agent is asked to
create data channels with SCTP stream identifiers
contained in the SDP offer if the SDP offer is accepted."</t>
<t>In <xref target="close-dc"/> t
he third paragraph began with
"A data channel can be closed by sending a new SDP offer which
excludes the dcmap and dcsa attribute lines for the data channel.
The port value for the m line SHOULD NOT be changed (e.g., to zero)
when closing a data channel (unless all data channels are being
closed and the SCTP association is no longer needed), since this
would close the SCTP association and impact all of the data channels.
If the answerer accepts the SDP offer then it MUST also exclude the
corresponding attribute lines in the answer. ..."
Replacement of this part with
"The intention to close a data channel can be signaled
by sending a new SDP offer which
excludes the "a=dcmap:" and "a=dcsa:" attribute lines for the data channel.
The port value for the "m" line SHOULD NOT be changed (e.g., to zero)
when closing a data channel (unless all data channels are being
closed and the SCTP association is no longer needed), since this
would close the SCTP association and impact all of the data channels.
If the answerer accepts the SDP offer then it MUST close those data channels
whose "a=dcmap:" and "a=dcsa:" attribute lines were excluded from the receive
d
SDP offer, unless those data channels were already closed,
and it MUST also exclude the
corresponding attribute lines in the answer."</t>
<t>In <xref target="close-dc"/> t
he hanging text after the third paragraph was
"This delayed close is to handle cases where a successful SDP
answer is not received, in which case the state of session should
be kept per the last successful SDP offer/answer."
Replacement of this sentence with
"This delayed closure is RECOMMENDED in order
to handle cases where a successful SDP answer is not received, in
which case the state of the session SHOULD be kept per the last
successful SDP offer/answer."</t>
<t>Although dedicated to "a=dcmap
" and "a=dcsa" SDP syntax aspects
<xref target="subsec-sdp-attr-for-dc-par-neg"/> contained already
procedural descriptions related to data channel reliability negotiation.
Creation of new <xref target="param_negotiation"/> and moval of
reliability negotiation related text to this new section.</t>
</list>
</t>
</section>
<section title="Changes against 'draft-ejzak-mmusic-data-
channel-sdpneg-02'">
<t>
<list style="symbols">
<t>Removal of note "ACTION ITEM"
from section "subprotocol parameter".
As <xref target="I-D.ietf-rtcweb-data-protocol"/> this document should refer
to IANA's
WebSocket Subprotocol Name Registry defined in <xref target="RFC6455"/>
</t>
<t>In whole document, replacement
of "unreliable" with "partially reliable",
which is used in <xref target="I-D.ietf-rtcweb-data-channel"/> and in
<xref target="I-D.ietf-rtcweb-data-protocol"/> in most places.</t>
<t>Clarification of the semantic
if the "max-retr" parameter is not present in
an "a=dcmap" attribute line. In section "max-retr parameter" the sentence
"The max-retr parameter is optional with default value unbounded"
was replaced with "The max-retr parameter is optional. If
the max-retr parameter is not present, then the maximal number of
retransmissions is determined as per the generic SCTP retransmission
rules as specified in <xref target="RFC4960"/>".</t>
<t>Clarification of the semantic
if the "max-time" parameter is not present in
an "a=dcmap" attribute line. In section "max-time parameter" the sentence
"The max-time parameter is optional with default value unbounded"
was replaced with "The max-time parameter is optional. If
the max-time parameter is not present, then the generic SCTP
retransmission timing rules apply as specified in <xref target="RFC4960"/>".<
/t>
<t>In section "label parameter" t
he sentence "Label is a mandatory parameter."
was removed and following new sentences (including the note) were added:
"The 'label' parameter is optional. If it is not
present, then its value defaults to the empty string.
Note: The empty string may also be explicitly used as 'label' value,
such that 'label=""' is equivalent to the 'label' parameter not being
present at all.
<xref target="I-D.ietf-rtcweb-data-protocol"/> allows the DATA_CHANNEL_OPEN
message's 'Label' value to be an empty string."</t>
<t>In section "subprotocol parame
ter" the sentence
"subprotocol is a mandatory parameter." was replaced with
"'subprotocol' is an optional
parameter. If the 'subprotocol' parameter is not present, then its
value defaults to the empty string."</t>
<t>In the "Examples" section, in
the first two SDP offer examples in
the "a=dcmap" attribute lines 'label="BGCP"' was replaced with 'label="bfcp"'
.</t>
<t>In all examples, the "m" line
proto value "DTLS/SCTP" was replaced with
"UDP/DTLS/SCTP" and the "a=fmtp" attribute lines were replaced with
"a=max-message-size" attribute lines, as per draft-ietf-mmusic-sctp-sdp-12.</
t>
</list>
</t>
</section>
<section title="Changes against '-01'">
<t>
<list style="symbols">
<t>Formal syntax for dcmap and dc
sa attribute lines. </t>
<t>Making subprotocol as an optio
nal parameter in dcmap. </t>
<t>Specifying disallowed paramete
r combinations for max-time and max-retr. </t>
<t>Clarifications on WebRTC data
channel close procedures. </t>
</list>
</t>
</section>
<section title="Changes against '-00'">
<t>
<list style="symbols">
<t> Revisions to identify differe
nce between internal and external
negotiation and their usage.</t>
<t>Introduction of more generic t
erminology, e.g. "application" instead of
"browser".</t>
<t>Clarification of how "max-retr
and max-time affect the usage of
unreliable and reliable WebRTC data channels.</t>
<t>Updates of examples to take in
to account the SDP syntax changes
introduced with draft-ietf-mmusic-sctp-sdp-07.</t>
<t>Removal of the SCTP port numbe
r from the "a=dcmap" and "a=dcsa" attributes
as this is now contained in the a=sctp-port attribute,
and as draft-ietf-mmusic-sctp-sdp-07 supports only one SCTP association
on top of the DTLS connection.</t>
</list>
</t>
</section>
</section>
</middle>
<back>
<references title="Normative References">
&RFC2119;
&RFC4960;
&RFC8174;
&RFC3264;
&RFC5234;
&RFC6525;
&RFC3629;
&DATAREQ;
&SDPBIS;
&SDPSCTP;
&SDPMUXATTR;
&DATAPROTO;
</references>
<references title="Informative References">
&RFC4582;
&RFC4975;
&RFC6455;
&CLUEDATA;
&MSRPDATA;
<reference anchor="WebRtcAPI" target="https://www.w3.org/
TR/2018/CR-webrtc-20180927/">
<front>
<title>
WebRTC 1.0: Real-time Communication Between Browsers
</title>
<author initials="A." surname="Bergkvist"
fullname="Adam Bergkvist">
<organization/>
</author>
<author initials="D." surname="Burnett" f
ullname="Daniel Burnett">
<organization/>
</author>
<author initials="C." surname="Jennings"
fullname="Cullen Jennings">
<organization/>
</author>
<author initials="A." surname="Narayanan"
fullname="Anant Narayanan">
<organization/>
</author>
<author initials="B." surname="Aboba" ful
lname="Bernard Aboba">
<organization/>
</author>
<author initials="T." surname="Brandstett
er" fullname="Taylor Brandstetter">
<organization/>
</author>
<author initials="J." surname="Bruaroey"
fullname="Jan-Ivar Bruaroey">
<organization/>
</author>
<date month="September" day="27" year="20
18"/>
</front>
<seriesInfo name="World Wide Web Consortium CR" v
alue="CR-webrtc-20180927"/>
<format type="HTML" target="https://www.w3.org/TR
/2018/CR-webrtc-20180927"/>
</reference>
</references>
<section title="Generic Data Channel Negotiation Aspects When Not
Using DCEP" anchor="generic-out-of-band-aspects">
<t>This appendix summarizes how data channels work in gen
eral and discusses
some key aspects, which should be considered for the out-of-band negotiation
of data
channels if DCEP is not used.</t> channels if DCEP is not used.</t>
<t>A WebRTC application creates a data channel <t indent="0" pn="section-appendix.a-2">A WebRTC application creates a dat a channel
by providing a number of setup parameters (subprotocol, label, by providing a number of setup parameters (subprotocol, label,
maximal number of retransmissions, maximal retransmission time, order of deli very, maximal number of retransmissions, maximal retransmission time, order of deli very,
priority). The application also specifies priority). The application also specifies whether
if it wants to make use of the negotiation using the DCEP it wants to make use of the negotiation using DCEP
<xref target="I-D.ietf-rtcweb-data-protocol"/>, or if the application <xref target="RFC8832" format="default" sectionFormat="of" derivedContent="RF
C8832"/> or
intends to negotiate data channels using the SDP offer/answer protocol.</t> intends to negotiate data channels using the SDP offer/answer protocol.</t>
<t>In any case, the SDP offer generated by the applicatio <t indent="0" pn="section-appendix.a-3">In any case, the SDP offer generat
n is per ed by the application is per
<xref target="I-D.ietf-mmusic-sctp-sdp"/>. In brief, it contains one <xref target="RFC8841" format="default" sectionFormat="of" derivedContent="RF
"m" line for the SCTP association on top of which data channels will run:</t> C8841"/>. In brief, it contains one
<figure align="left" title=""> "m=" line for the SCTP association on top of which the data channels will run
<artwork align="left"><![CDATA[ :
</t>
<sourcecode name="app-a-sdp-example" type="sdp" markers="false" pn="sectio
n-appendix.a-4">
m=application 54111 UDP/DTLS/SCTP webrtc-datachannel m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
a=max-message-size:100000 a=max-message-size:100000
a=sctp-port:5000 a=sctp-port:5000
a=tls-id:abc3de65cddef001be82 a=tls-id:abc3de65cddef001be82
a=setup:actpass a=setup:actpass
a=fingerprint:SHA-1 \ a=fingerprint:SHA-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB</sourcecode>
]]></artwork> <aside pn="section-appendix.a-5">
</figure> <t indent="0" pn="section-appendix.a-5.1">Note: A WebRTC application wil
<t>Note: A WebRTC application will only use "m" line form l only use the "m=" line format "webrtc-datachannel"
at "webrtc-datachannel", and will not use other formats in the "m=" line for other protocols
and will not use other formats in the "m" line for other protocols such as T.38 <xref target="T38" format="default" sectionFormat="of" derivedCo
such as t38. ntent="T38"/>.
<xref target="I-D.ietf-mmusic-sctp-sdp"/> supports only one SCTP <xref target="RFC8841" format="default" sectionFormat="of" derivedContent="RF
C8841"/> supports only one SCTP
association to be established on top of a DTLS association. association to be established on top of a DTLS association.
</t> </t>
<t>Note: The above SDP media description does not contain </aside>
any channel-specific <aside pn="section-appendix.a-6">
<t indent="0" pn="section-appendix.a-6.1">Note: The above SDP media desc
ription does not contain any channel-specific
information.</t> information.</t>
<section title="Stream Identifier Numbering" anchor="si_n </aside>
um"> <section anchor="si_num" numbered="true" removeInRFC="false" toc="include"
<t>Independently from the requested type of negot pn="section-a.1">
iation, the application <name slugifiedName="name-stream-identifier-numbering">Stream Identifier
creating a data channel can either pass the stream identifier to the data ch Numbering</name>
annel stack to assign <t indent="0" pn="section-a.1-1">Independently from the requested type o
to the data channel or else let the data channel stack pick f negotiation, the application
creating a data channel can either (1) pass the stream identifier to the dat
a channel stack to assign
to the data channel or (2) let the data channel stack pick
one identifier from the unused ones.</t> one identifier from the unused ones.</t>
<t>To avoid glare situations <xref target="RFC326 4"/>, each endpoint can moreover own an <t indent="0" pn="section-a.1-2">Moreover, to avoid glare situations <xr ef target="RFC3264" format="default" sectionFormat="of" derivedContent="RFC3264" />, each endpoint can own an
exclusive set of stream identifiers, in which case an endpoint can exclusive set of stream identifiers, in which case an endpoint can
only create a data channel with a stream identifier it owns.</t> only create a data channel with a stream identifier it owns.</t>
<t>Which set of stream identifiers is owned by wh ich endpoint is <t indent="0" pn="section-a.1-3">Which set of stream identifiers is owne d by which endpoint is
determined by convention or other means. determined by convention or other means.
<list style="hanging"> </t>
<t>Note:For data channels negotia <aside pn="section-a.1-4">
ted with the DCEP, one endpoint owns by <t indent="0" pn="section-a.1-4.1">Note: For data channels negotiated
with DCEP, one endpoint owns by
convention the even stream identifiers, whereas the other owns the convention the even stream identifiers, whereas the other owns the
odd stream identifiers, as defined in odd stream identifiers, as defined in
<xref target="I-D.ietf-rtcweb-data-protocol"/>.</t> <xref target="RFC8832" format="default" sectionFormat="of" derivedContent=
<t>Note:For data channels negotia "RFC8832"/>.</t>
ted via different protocol from DCEP, </aside>
<aside pn="section-a.1-5">
<t indent="0" pn="section-a.1-5.1">Note: For data channels negotiated
via a protocol other than DCEP,
no convention is defined by default.</t> no convention is defined by default.</t>
</list> </aside>
</t> </section>
</section> <section anchor="sec-gen-ext-neg" numbered="true" removeInRFC="false" toc=
<section title="Generic Data Channel Negotiation Not Usin "include" pn="section-a.2">
g DCEP" anchor="sec-gen-ext-neg"> <name slugifiedName="name-generic-data-channel-negotia">Generic Data Cha
<section title="Overview"> nnel Negotiation Not Using DCEP</name>
<t>DCEP negotiation only provides for neg <section numbered="true" removeInRFC="false" toc="include" pn="section-a
otiation of data channel .2.1">
transport parameters and does not provide for negotiation of subprotocol <name slugifiedName="name-overview">Overview</name>
specific parameters. DCEP-less data channel negotiation can be defined to <t indent="0" pn="section-a.2.1-1">DCEP negotiation only provides for
negotiation of data channel
transport parameters and does not provide for negotiation of
subprotocol-specific parameters. Non-DCEP data channel negotiation can be d
efined to
allow negotiation of parameters beyond those handled by DCEP, allow negotiation of parameters beyond those handled by DCEP,
e.g., parameters specific to the subprotocol instantiated on a e.g., parameters specific to the subprotocol instantiated on a
particular data channel.</t> particular data channel.</t>
<t>The following procedures are common to all methods of data channel <t indent="0" pn="section-a.2.1-2">The following procedures are common to all methods of data channel
negotiation not using DCEP, whether in-band (communicated using proprietary means on negotiation not using DCEP, whether in-band (communicated using proprietary means on
an already established data channel) or out-of-band (using SDP offer/answer an already-established data channel) or out-of-band (using the SDP
or offer/answer mechanism or
some other protocol associated with the signaling channel).</t> some other protocol associated with the signaling channel).</t>
</section> </section>
<section title="Opening a Data Channel" anchor="e <section anchor="ext_open" numbered="true" removeInRFC="false" toc="incl
xt_open"> ude" pn="section-a.2.2">
<t>In the case of DCEP-less negotiation, <name slugifiedName="name-opening-a-data-channel">Opening a Data Chann
the endpoint application has the el</name>
option to fully control the stream identifier assignments. However <t indent="0" pn="section-a.2.2-1">In the case of non-DCEP negotiation
, the endpoint application has the
option to fully control the stream identifier assignments. However,
these assignments have to coexist with the assignments controlled by these assignments have to coexist with the assignments controlled by
the data channel stack for the DCEP negotiated data channels (if the data channel stack for data channels negotiated using DCEP (if
any). It is the responsibility of the application to ensure consistent any). It is the responsibility of the application to ensure consistent
assignment of stream identifiers.</t> assignment of stream identifiers.</t>
<t>When the application requests the crea <t indent="0" pn="section-a.2.2-2">When the application requests that
tion of a new data channel to the creation of a new data channel
be set up via DCEP-less negotiation, the data channel stack creates be set up via non-DCEP negotiation, the data channel stack creates
the data channel locally without sending any DATA_CHANNEL_OPEN message the data channel locally without sending any DATA_CHANNEL_OPEN messages
in-band. in-band.
However, even if the ICE (Interactive Connectivity Establishment), However, even if the ICE (Interactive Connectivity Establishment),
DTLS and SCTP procedures were already successfully DTLS, and SCTP procedures were already successfully
completed, the application can't send data on this data channel until the completed, the application can't send data on this data channel until the
negotiation is complete with the peer. This is because the peer needs negotiation with the peer is complete. This is because the peer needs
to be aware of and accept the usage of this data channel. The to be aware of and accept the usage of this data channel. The
peer, after accepting the data channel offer, can start sending data peer, after accepting the data channel offer, can start sending data
immediately. This implies that the offerer may receive data channel immediately. This implies that the offerer may receive data channel
subprotocol messages subprotocol messages
before the negotiation is complete and the application should be before the negotiation is complete, and the application should be
ready to handle it.</t> ready to handle it.</t>
<t>If the peer rejects the data channel p <t indent="0" pn="section-a.2.2-3">If the peer rejects the data channe
art of the offer then it l part of the offer, then it
doesn't have to do anything as the data channel was not created using doesn't have to do anything, as the data channel was not created using
the stack. The offerer on the other hand needs to close the data the stack. The offerer, on the other hand, needs to close the data
channel that was opened by invoking relevant data channel stack API channel that was opened by invoking relevant data channel stack API
procedures.</t> procedures.</t>
<t>It is also worth noting that a data ch <t indent="0" pn="section-a.2.2-4">It is also worth noting that a data
annel stack implementation may channel stack implementation may
not provide any API to create and close data channels; instead the not provide any APIs to create and close data channels; instead, the
data channels may be used on the fly as needed just by communicating data channels may be used on the fly as needed, just by communicating
via non-DCEP means or by even having some local configuration/assumptions via non-DCEP means or even by having some local configuration/assumptions
on both the peers.</t> on both of the peers.</t>
<t>The application then negotiates the da <t indent="0" pn="section-a.2.2-5">The application then negotiates the
ta channel data channel
properties and subprotocol properties with the peer's application properties and subprotocol properties with the peer's application
using a mechanism different from DCEP.</t> using a mechanism different from DCEP.</t>
<t>The peer then symmetrically creates a data channel <t indent="0" pn="section-a.2.2-6">The peer then symmetrically creates a data channel
with these negotiated data channel properties. This is the only way with these negotiated data channel properties. This is the only way
for the peer's data channel stack to know which properties to apply for the peer's data channel stack to know which properties to apply
when transmitting data on this channel. when transmitting data on this channel.
The data channel stack must The data channel stack must
allow data channel creation with any non-conflicting stream identifier allow data channel creation with any nonconflicting stream identifier
so that both peers can create the data channel with the same so that both peers can create the data channel with the same
stream identifier. stream identifier.
</t> </t>
</section> </section>
<section title="Closing a Data Channel"> <section numbered="true" removeInRFC="false" toc="include" pn="section-a
<t>When the application requests the clos .2.3">
ing of a <name slugifiedName="name-closing-a-data-channel-2">Closing a Data Cha
nnel</name>
<t indent="0" pn="section-a.2.3-1">When the application requests the c
losing of a
data channel negotiated without DCEP, data channel negotiated without DCEP,
the data channel stack always performs an SCTP SSN the data channel stack always performs an SCTP SSN
reset for this channel.</t> Reset for this channel.</t>
<t>Depending upon the method used for DCE <t indent="0" pn="section-a.2.3-2">Depending upon the method used for
P-less negotiation and the non-DCEP negotiation and the
subprotocol associated with the data channel, the closing might in subprotocol associated with the data channel, the closing of the data chann
addition be signaled to the peer via SDP offer/answer negotiation.</t> el might also be signaled to the peer via SDP offer/answer negotiation.</t>
</section> </section>
</section> </section>
<!-- sec-gen-ext-neg --> </section>
</section> <section anchor="acknowledgements" numbered="false" removeInRFC="false" toc=
<!-- generic-out-of-band-aspects --> "include" pn="section-appendix.b">
</back> <name slugifiedName="name-acknowledgements">Acknowledgements</name>
<t indent="0" pn="section-appendix.b-1">The authors wish to acknowledge th
e borrowing of ideas from other
draft documents by <contact fullname="Salvatore Loreto"/>, <contact fullname=
"Gonzalo Camarillo"/>, <contact fullname="Peter Dunkley"/>, and
<contact fullname="Gavin Llewellyn"/>. The authors also wish to thank <contac
t fullname="Flemming Andreasen"/>, <contact fullname="Christian Groves"/>,
<contact fullname="Gunnar Hellström"/>, <contact fullname="Paul Kyzivat"/>
, <contact fullname="Jonathan Lennox"/>,
<contact fullname="Uwe Rauschenbach"/>, and <contact fullname="Roman Shpount"
/> for their invaluable comments.</t>
<t indent="0" pn="section-appendix.b-2">Special thanks to <contact fullnam
e="Christer Holmberg"/> for helping
finish the document and cleaning up <xref target="section_procedures" form
at="default" sectionFormat="of" derivedContent="Section 6"/>.
</t>
</section>
<section anchor="contributors" numbered="false" removeInRFC="false" toc="inc
lude" pn="section-appendix.c">
<name slugifiedName="name-contributors">Contributors</name>
<t indent="0" pn="section-appendix.c-1"><contact fullname="Juergen Stoetze
r-Bradler"/> made significant
contributions to this document and should be considered a coauthor.</t>
</section>
<section anchor="authors-addresses" numbered="false" removeInRFC="false" toc
="include" pn="section-appendix.d">
<name slugifiedName="name-authors-addresses">Authors' Addresses</name>
<author initials="K." surname="Drage" fullname="Keith Drage">
<organization showOnFrontPage="true">Unaffiliated</organization>
<address>
<email>drageke@ntlworld.com</email>
</address>
</author>
<author initials="M." surname="Makaraju" fullname="Maridi R. Makaraju (Raj
u)">
<organization showOnFrontPage="true">Unaffiliated</organization>
<address>
<email>mmraju@gmail.com</email>
</address>
</author>
<author fullname="Richard Ejzak" initials="R." surname="Ejzak">
<organization showOnFrontPage="true">Unaffiliated</organization>
<address>
<email>richard.ejzak@gmail.com</email>
</address>
</author>
<author fullname="Jerome Marcon" initials="J." surname="Marcon">
<organization showOnFrontPage="true">Unaffiliated</organization>
<address>
<email>jeromee.marcon@free.fr</email>
</address>
</author>
<author initials="R." surname="Even" fullname="Roni Even" role="editor">
<organization showOnFrontPage="true"/>
<address>
<email>ron.even.tlv@gmail.com</email>
</address>
</author>
</section>
</back>
</rfc> </rfc>
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