rfc8839v5.txt		rfc8839.txt
	Internet Engineering Task Force (IETF) M. Petit-Huguenin		Internet Engineering Task Force (IETF) M. Petit-Huguenin
	Request for Comments: 8839 Impedance Mismatch		Request for Comments: 8839 Impedance Mismatch
	Obsoletes: 5245, 6336 S. Nandakumar		Obsoletes: 5245, 6336 S. Nandakumar
	Category: Standards Track Cisco Systems		Category: Standards Track Cisco Systems
	ISSN: 2070-1721 C. Holmberg		ISSN: 2070-1721 C. Holmberg
	A. Keränen		A. Keränen
	Ericsson		Ericsson
	R. Shpount		R. Shpount
	TurboBridge		TurboBridge
	June 2020		January 2021
	Session Description Protocol (SDP) Offer/Answer Procedures for		Session Description Protocol (SDP) Offer/Answer Procedures for
	Interactive Connectivity Establishment (ICE)		Interactive Connectivity Establishment (ICE)
	Abstract		Abstract
	This document describes Session Description Protocol (SDP) Offer/		This document describes Session Description Protocol (SDP) Offer/
	Answer procedures for carrying out Interactive Connectivity		Answer procedures for carrying out Interactive Connectivity
	Establishment (ICE) between the agents.		Establishment (ICE) between the agents.
	skipping to change at line 40 ¶		skipping to change at line 40 ¶
	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/rfc8839.		https://www.rfc-editor.org/info/rfc8839.
	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
	skipping to change at line 313 ¶		skipping to change at line 313 ¶
	This specification provides no guidance on how an agent should		This specification provides no guidance on how an agent should
	proceed in the cases where the above condition is not met with the		proceed in the cases where the above condition is not met with the
	few exceptions noted below:		few exceptions noted below:
	1. The presence of certain Application Layer Gateways might modify		1. The presence of certain Application Layer Gateways might modify
	the transport address information as described in Section 8. The		the transport address information as described in Section 8. The
	behavior of the responding agent in such a situation is		behavior of the responding agent in such a situation is
	implementation dependent. Informally, the responding agent might		implementation dependent. Informally, the responding agent might
	consider the mismatched transport address information as a		consider the mismatched transport address information as a
	plausible new candidate learnt from the peer and continue its ICE		plausible new candidate learned from the peer and continue its
	processing with that transport address included. Alternatively,		ICE processing with that transport address included.
	the responding agent MAY include an "ice-mismatch" attribute in		Alternatively, the responding agent MAY include an "ice-mismatch"
	its answer for such data streams. If an agent chooses to include		attribute in its answer for such data streams. If an agent
	an "ice-mismatch" attribute in its answer for a data stream, then		chooses to include an "ice-mismatch" attribute in its answer for
	it MUST also omit "candidate" attributes, MUST terminate the		a data stream, then it MUST also omit "candidate" attributes,
	usage of ICE procedures, and [RFC3264] procedures MUST be used		MUST terminate the usage of ICE procedures, and [RFC3264]
	instead for this data stream.		procedures MUST be used instead for this data stream.
	2. The transport address from the peer for the default destination		2. The transport address from the peer for the default destination
	is set to IPv4/IPv6 address values "0.0.0.0"/"::" and port value		is set to IPv4/IPv6 address values "0.0.0.0"/"::" and port value
	of "9". This MUST NOT be considered as a ICE failure by the peer		of "9". This MUST NOT be considered as an ICE failure by the
	agent, and the ICE processing MUST continue as usual.		peer agent, and the ICE processing MUST continue as usual.
	3. In some cases, the controlling/initiator agent may receive an SDP		3. In some cases, the controlling/initiator agent may receive an SDP
	answer that may omit "candidate" attributes for the data stream,		answer that may omit "candidate" attributes for the data stream,
	and instead include a media-level "ice-mismatch" attribute. This		and instead include a media-level "ice-mismatch" attribute. This
	signals to the offerer that the answerer supports ICE, but that		signals to the offerer that the answerer supports ICE, but that
	ICE processing was not used for this data stream. In this case,		ICE processing was not used for this data stream. In this case,
	ICE processing MUST be terminated for this data stream, and		ICE processing MUST be terminated for this data stream, and
	[RFC3264] procedures MUST be followed instead.		[RFC3264] procedures MUST be followed instead.
	4. The transport address from the peer for the default destination		4. The transport address from the peer for the default destination
	is an FQDN. Regardless of the procedures used to resolve FQDN or		is an FQDN. Regardless of the procedures used to resolve FQDN or
	the resolution result, this MUST NOT be considered as a ICE		the resolution result, this MUST NOT be considered as an ICE
	failure by the peer agent, and the ICE processing MUST continue		failure by the peer agent, and the ICE processing MUST continue
	as usual.		as usual.
	4.2.6. SDP Example		4.2.6. SDP Example
	The following is an example SDP message that includes ICE attributes		The following is an example SDP message that includes ICE attributes
	(lines folded for readability):		(lines folded for readability):
	v=0		v=0
	o=jdoe 2890844526 2890842807 IN IP4 203.0.113.141		o=jdoe 2890844526 2890842807 IN IP4 203.0.113.141
	skipping to change at line 491 ¶		skipping to change at line 491 ¶
	streams to zero (Section 4.4.1.1.2), even if the peer did indicate		streams to zero (Section 4.4.1.1.2), even if the peer did indicate
	support for the 'ice2' ice-option. If needed, such offer is used to		support for the 'ice2' ice-option. If needed, such offer is used to
	align the connection address, port, and transport protocol, as		align the connection address, port, and transport protocol, as
	described above.		described above.
	As described in [RFC8445], once the controlling agent has nominated a		As described in [RFC8445], once the controlling agent has nominated a
	candidate pair for a checklist, the agent MUST NOT nominate another		candidate pair for a checklist, the agent MUST NOT nominate another
	pair for that checklist during the lifetime of the ICE session (i.e.,		pair for that checklist during the lifetime of the ICE session (i.e.,
	until ICE is restarted).		until ICE is restarted).
	[ICE-PAC] provides a mechanism for allowing the ICE process to run		[RFC8863] provides a mechanism for allowing the ICE process to run
	long enough in order to find working candidate pairs, by waiting for		long enough in order to find working candidate pairs, by waiting for
	potential peer-reflexive candidates, even though no candidate pairs		potential peer-reflexive candidates, even though no candidate pairs
	were received from the peer or all current candidate pairs associated		were received from the peer or all current candidate pairs associated
	with a checklist have either failed or been discarded.		with a checklist have either failed or been discarded.
	4.4. Subsequent Offer/Answer Exchanges		4.4. Subsequent Offer/Answer Exchanges
	Either agent MAY generate a subsequent offer at any time allowed by		Either agent MAY generate a subsequent offer at any time allowed by
	[RFC3264]. This section defines rules for construction of subsequent		[RFC3264]. This section defines rules for construction of subsequent
	offers and answers.		offers and answers.
	skipping to change at line 1707 ¶		skipping to change at line 1707 ¶
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive		[RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
	Connectivity Establishment (ICE): A Protocol for Network		Connectivity Establishment (ICE): A Protocol for Network
	Address Translator (NAT) Traversal", RFC 8445,		Address Translator (NAT) Traversal", RFC 8445,
	DOI 10.17487/RFC8445, July 2018,		DOI 10.17487/RFC8445, July 2018,
	<https://www.rfc-editor.org/info/rfc8445>.		<https://www.rfc-editor.org/info/rfc8445>.
	12.2. Informative References		12.2. Informative References
	[ICE-PAC] Holmberg, C. and J. Uberti, "Interactive Connectivity
	Establishment Patiently Awaiting Connectivity (ICE PAC)",
	Work in Progress, Internet-Draft, draft-ietf-ice-pac-06,
	29 April 2020,
	<https://tools.ietf.org/html/draft-ietf-ice-pac-06>.
	[RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.		[RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.
	Camarillo, "Best Current Practices for Third Party Call		Camarillo, "Best Current Practices for Third Party Call
	Control (3pcc) in the Session Initiation Protocol (SIP)",		Control (3pcc) in the Session Initiation Protocol (SIP)",
	BCP 85, RFC 3725, DOI 10.17487/RFC3725, April 2004,		BCP 85, RFC 3725, DOI 10.17487/RFC3725, April 2004,
	<https://www.rfc-editor.org/info/rfc3725>.		<https://www.rfc-editor.org/info/rfc3725>.
	[RFC3960] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing		[RFC3960] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing
	Tone Generation in the Session Initiation Protocol (SIP)",		Tone Generation in the Session Initiation Protocol (SIP)",
	RFC 3960, DOI 10.17487/RFC3960, December 2004,		RFC 3960, DOI 10.17487/RFC3960, December 2004,
	<https://www.rfc-editor.org/info/rfc3960>.		<https://www.rfc-editor.org/info/rfc3960>.
	skipping to change at line 1759 ¶		skipping to change at line 1753 ¶
	for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675,		for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675,
	October 2015, <https://www.rfc-editor.org/info/rfc7675>.		October 2015, <https://www.rfc-editor.org/info/rfc7675>.
	[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for		[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
	Writing an IANA Considerations Section in RFCs", BCP 26,		Writing an IANA Considerations Section in RFCs", BCP 26,
	RFC 8126, DOI 10.17487/RFC8126, June 2017,		RFC 8126, DOI 10.17487/RFC8126, June 2017,
	<https://www.rfc-editor.org/info/rfc8126>.		<https://www.rfc-editor.org/info/rfc8126>.
	[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, June 2020,		DOI 10.17487/RFC8859, January 2021,
	<https://www.rfc-editor.org/info/rfc8859>.		<https://www.rfc-editor.org/info/rfc8859>.
			[RFC8863] Holmberg, C. and J. Uberti, "Interactive Connectivity
			Establishment Patiently Awaiting Connectivity (ICE PAC)",
			RFC 8863, DOI 10.17487/RFC8863, January 2021,
			<https://www.rfc-editor.org/info/rfc8863>.
	Appendix A. Examples		Appendix A. Examples
	For the example shown in Section 15 of [RFC8445], the resulting offer		For the example shown in Section 15 of [RFC8445], the resulting offer
	(message 5) encoded in SDP looks like (lines folded for clarity):		(message 5) encoded in SDP looks like (lines folded for clarity):
	v=0		v=0
	o=jdoe 2890844526 2890842807 IN IP6 $L-PRIV-1.IP		o=jdoe 2890844526 2890842807 IN IP6 $L-PRIV-1.IP
	s=		s=
	c=IN IP6 $NAT-PUB-1.IP		c=IN IP6 $NAT-PUB-1.IP
	t=0 0		t=0 0
	skipping to change at line 1800 ¶		skipping to change at line 1799 ¶
	c=IN IP6 2001:db8:8101:3a55:4858:a2a9:22ff:99b9		c=IN IP6 2001:db8:8101:3a55:4858:a2a9:22ff:99b9
	t=0 0		t=0 0
	a=ice-options:ice2		a=ice-options:ice2
	a=ice-pacing:50		a=ice-pacing:50
	a=ice-pwd:asd88fgpdd777uzjYhagZg		a=ice-pwd:asd88fgpdd777uzjYhagZg
	a=ice-ufrag:8hhY		a=ice-ufrag:8hhY
	m=audio 45664 RTP/AVP 0		m=audio 45664 RTP/AVP 0
	b=RS:0		b=RS:0
	b=RR:0		b=RR:0
	a=rtpmap:0 PCMU/8000		a=rtpmap:0 PCMU/8000
	a=candidate:1 1 UDP 2130706431 fe80::6676:baff:fe9c:ee4a 8998 typ host		a=candidate:1 1 UDP 2130706431 fe80::6676:baff:fe9c:ee4a 8998
			typ host
	a=candidate:2 1 UDP 1694498815 2001:db8:8101:3a55:4858:a2a9:22ff:99b9		a=candidate:2 1 UDP 1694498815 2001:db8:8101:3a55:4858:a2a9:22ff:99b9
	45664 typ srflx raddr fe80::6676:baff:fe9c:ee4a rport 8998		45664 typ srflx raddr fe80::6676:baff:fe9c:ee4a rport 8998
	The resulting answer looks like:		The resulting answer looks like:
	v=0		v=0
	o=bob 2808844564 2808844564 IN IP4 $R-PUB-1.IP		o=bob 2808844564 2808844564 IN IP4 $R-PUB-1.IP
	s=		s=
	c=IN IP4 $R-PUB-1.IP		c=IN IP4 $R-PUB-1.IP
	t=0 0		t=0 0
End of changes. 10 change blocks.
	22 lines changed or deleted		22 lines changed or added
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