rfc8861v5.txt   rfc8861.txt 
Internet Engineering Task Force (IETF) J. Lennox Internet Engineering Task Force (IETF) J. Lennox
Request for Comments: 8861 8x8 / Jitsi Request for Comments: 8861 8x8 / Jitsi
Category: Standards Track M. Westerlund Category: Standards Track M. Westerlund
ISSN: 2070-1721 Ericsson ISSN: 2070-1721 Ericsson
Q. Wu Q. Wu
Huawei Huawei
C. Perkins C. Perkins
University of Glasgow University of Glasgow
September 2020 January 2021
Sending Multiple RTP Streams in a Single RTP Session: Grouping RTP Sending Multiple RTP Streams in a Single RTP Session: Grouping RTP
Control Protocol (RTCP) Reception Statistics and Other Feedback Control Protocol (RTCP) Reception Statistics and Other Feedback
Abstract Abstract
RTP allows multiple RTP streams to be sent in a single session but RTP allows multiple RTP streams to be sent in a single session but
requires each Synchronization Source (SSRC) to send RTP Control requires each Synchronization Source (SSRC) to send RTP Control
Protocol (RTCP) reception quality reports for every other SSRC Protocol (RTCP) reception quality reports for every other SSRC
visible in the session. This causes the number of RTCP reception visible in the session. This causes the number of RTCP reception
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received public review and has been approved for publication by the received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841. Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8861. https://www.rfc-editor.org/info/rfc8861.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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example, it would make no sense for an SSRC that is receiving video example, it would make no sense for an SSRC that is receiving video
to send a Voice over IP (VoIP) metric RTCP XR report block. Such to send a Voice over IP (VoIP) metric RTCP XR report block. Such
media-specific RTCP XR report blocks MUST be sent by the SSRC to media-specific RTCP XR report blocks MUST be sent by the SSRC to
which they are relevant and MUST NOT be included in the common report which they are relevant and MUST NOT be included in the common report
sent by the reporting source. This might mean that some SSRCs send sent by the reporting source. This might mean that some SSRCs send
RTCP XR packets in compound RTCP packets that contain an empty RTCP RTCP XR packets in compound RTCP packets that contain an empty RTCP
SR/RR packet and that the time period covered by the RTCP XR packet SR/RR packet and that the time period covered by the RTCP XR packet
is different from that covered by the RTCP SR/RR packet. If it is is different from that covered by the RTCP SR/RR packet. If it is
important that the RTCP XR packet and RTCP SR/RR packet cover the important that the RTCP XR packet and RTCP SR/RR packet cover the
same time period, then that source SHOULD be removed from the RTCP same time period, then that source SHOULD be removed from the RTCP
Reporting Group, and standard RTCP packets are sent instead. Reporting Group, and standard RTCP packets be sent instead.
3.5. Middlebox Considerations 3.5. Middlebox Considerations
Many different types of middleboxes are used with RTP. RTCP Many different types of middleboxes are used with RTP. RTCP
Reporting Groups are potentially relevant to those types of RTP Reporting Groups are potentially relevant to those types of RTP
middleboxes that have their own SSRCs and generate RTCP reports for middleboxes that have their own SSRCs and generate RTCP reports for
the traffic they receive. RTP middleboxes that do not have their own the traffic they receive. RTP middleboxes that do not have their own
SSRC and that do not send RTCP reports on the traffic they receive SSRC and that do not send RTCP reports on the traffic they receive
cannot use the RTCP Reporting Group extension, since they generate no cannot use the RTCP Reporting Group extension, since they generate no
RTCP reports to that group. RTCP reports to that group.
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resource exhaustion attack on a receiver implementation. resource exhaustion attack on a receiver implementation.
Modification of the "List of SSRCs for the Reporting Source(s)" field Modification of the "List of SSRCs for the Reporting Source(s)" field
would change the SSRC the receiver expects to report on behalf of would change the SSRC the receiver expects to report on behalf of
this SSRC. If that SSRC exists, this situation could potentially this SSRC. If that SSRC exists, this situation could potentially
change the Reporting Group used for this SSRC. A change to another change the Reporting Group used for this SSRC. A change to another
Reporting Group belonging to another endpoint is likely detectable, Reporting Group belonging to another endpoint is likely detectable,
as there would be a mismatch between the SSRC of the packet sender's as there would be a mismatch between the SSRC of the packet sender's
endpoint information, transport addresses, SDES CNAME, etc., and the endpoint information, transport addresses, SDES CNAME, etc., and the
corresponding information from the Reporting Group indicated. corresponding information from the Reporting Group indicated.
In general, the Reporting Group is providing limited impacts attacks In general, the Reporting Group is providing limited-impact attacks
on the endpoints. The most significant result from a deliberate on the endpoints. The most significant result from a deliberate
attack would be to cause the information to be discarded or be attack would be to cause the information to be discarded or be
inconsistent, including the discarding of all RTCP packets that are inconsistent, including the discarding of all RTCP packets that are
modified. This causes a lack of information at any receiver entity, modified. This causes a lack of information at any receiver entity,
possibly disregarding the endpoint's participation in the session. possibly disregarding the endpoint's participation in the session.
To protect against such attacks from external non-trusted entities, To protect against such attacks from external non-trusted entities,
integrity and source authentication SHOULD be applied. This can be integrity and source authentication SHOULD be applied. This can be
done, for example, by using the Secure Real-time Transport Protocol done, for example, by using the Secure Real-time Transport Protocol
(SRTP) [RFC3711] with appropriate key management; other options (SRTP) [RFC3711] with appropriate key management; other options
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"Sending Multiple RTP Streams in a Single RTP Session", "Sending Multiple RTP Streams in a Single RTP Session",
RFC 8108, DOI 10.17487/RFC8108, March 2017, RFC 8108, DOI 10.17487/RFC8108, March 2017,
<https://www.rfc-editor.org/info/rfc8108>. <https://www.rfc-editor.org/info/rfc8108>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8859] Nandakumar, S., "A Framework for Session Description [RFC8859] Nandakumar, S., "A Framework for Session Description
Protocol (SDP) Attributes When Multiplexing", RFC 8859, Protocol (SDP) Attributes When Multiplexing", RFC 8859,
DOI 10.17487/RFC8859, September 2020, DOI 10.17487/RFC8859, January 2021,
<https://www.rfc-editor.org/info/rfc8859>. <https://www.rfc-editor.org/info/rfc8859>.
7.2. Informative References 7.2. Informative References
[RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
Announcement Protocol", RFC 2974, DOI 10.17487/RFC2974, Announcement Protocol", RFC 2974, DOI 10.17487/RFC2974,
October 2000, <https://www.rfc-editor.org/info/rfc2974>. October 2000, <https://www.rfc-editor.org/info/rfc2974>.
[RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
"RTP Control Protocol Extended Reports (RTCP XR)", "RTP Control Protocol Extended Reports (RTCP XR)",
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Jonathan Lennox Jonathan Lennox
8x8, Inc. / Jitsi 8x8, Inc. / Jitsi
Jersey City, NJ 07302 Jersey City, NJ 07302
United States of America United States of America
Email: jonathan.lennox@8x8.com Email: jonathan.lennox@8x8.com
Magnus Westerlund Magnus Westerlund
Ericsson Ericsson
Farogatan 2 Torshamnsgatan 23
SE-164 80 Kista SE-164 80 Kista
Sweden Sweden
Phone: +46 10 714 82 87
Email: magnus.westerlund@ericsson.com Email: magnus.westerlund@ericsson.com
Qin Wu Qin Wu
Huawei Huawei
101 Software Avenue, Yuhua District 101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012 Nanjing, Jiangsu 210012
China China
Email: bill.wu@huawei.com Email: bill.wu@huawei.com
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