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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) ** Obsolete normative reference: RFC 5285 (Obsoleted by RFC 8285) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Thatcher 3 Internet-Draft Google 4 Intended status: Standards Track March 9, 2015 5 Expires: September 10, 2015 7 Encoded Stream ID Header Extension 8 draft-pthatcher-avtext-esid-00 10 Abstract 12 This document defines a new RTP Header Extension and SDES item for an 13 Encoded Stream ID or "ESID" which can be used for either identifying 14 Encoded Streams or for extending RTP Payload Types. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on September 10, 2015. 33 Copyright Notice 35 Copyright (c) 2015 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 52 3. RTP/RTCP extensions for ESID value transport . . . . . . . . 2 53 3.1. RTP ESID Header Extension . . . . . . . . . . . . . . . . 3 54 3.2. RTP ESID SDES Item . . . . . . . . . . . . . . . . . . . 3 55 4. Representation as a fmt value . . . . . . . . . . . . . . . . 4 56 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4 57 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 58 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 59 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 60 9. Normative References . . . . . . . . . . . . . . . . . . . . 5 61 Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 5 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 64 1. Introduction 66 SDP Offerers and Answerers [RFC3264] can assign fmt values to SDP 67 Media Descriptions (m= lines) within SDP Offers and Answers, using 68 the procedures in [RFC4566]. Each fmt uniquely identifies a media 69 format, which is typically an RTP payload type. 71 fmt values are also used to identity an Encoded Stream, where each 72 combination of (Media Format, Encoded Stream) is represented as a 73 unique fmt value. For large numbers of Media Formats and Encoded 74 Streams, the number of fmts then can exceed what can typically fit in 75 an RTP payload type. 77 This specification defines a new RTP Header Extension and SDES item 78 for an Encoded Stream ID or "ESID" which can be used for either 79 identifying Encoded Streams or extending RTP Payload Types. It also 80 defines how these map to fmt values. 82 2. Terminology 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in [RFC2119]. 88 3. RTP/RTCP extensions for ESID value transport 90 This section defines a new RTP SDES item [RFC3264], 'ESID', which is 91 used to carry IDs for Encoded Streams values within RTCP SDES 92 packets. This section also defines a new RTP header extension 93 [RFC5285], which can be used to carry the ESID value in RTP packets. 95 The SDES item and RTP header extension makes is possible for a 96 receiver to associate received RTCP- and RTP packets with a specific 97 Encoded Stream. 99 The RTP MID SDES item SHOULD be sent in the first few RTCP packets 100 sent on joining the session, and SHOULD be sent regularly thereafter. 101 The exact number of RTCP packets in which this SDES item is sent is 102 intentionally not specified here, as it will depend on the expected 103 packet loss rate, the RTCP reporting interval, and the allowable 104 overhead. 106 The RTP ESID header extension SHOULD be included in some RTP packets 107 at the start of the session and whenever the SSRC changes. It might 108 also be useful to include the header extension in RTP packets that 109 comprise random access points in the media (e.g., with video 110 I-frames). The exact number of RTP packets in which this header 111 extension is sent is intentionally not specified here, as it will 112 depend on expected packet loss rate and loss patterns, the overhead 113 the application can tolerate, and the importance of immediate receipt 114 of the ESID value. 116 For robustness purpose, endpoints need to be prepared for situations 117 where the ESID value is delayed, and SHOULD NOT terminate sessions in 118 such cases, as the ESID value is likely to arrive soon. 120 3.1. RTP ESID Header Extension 122 The payload, containing the ESID value, of the RTP ESID header 123 extension element can be encoded using either the one-byte or two- 124 byte header [RFC5285]. 126 3.2. RTP ESID SDES Item 128 0 1 2 3 129 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 | ESID=TBD | length | ESID value ... 132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 [RFC EDITOR NOTE: Please replace TBD with the assigned SDES 135 identifier value.] 137 4. Representation as a fmt value 139 NOTE: The usage of other signalling protocols for carrying the ESID 140 value is not prevented, but the usage of such protocols is outside 141 the scope of this document. 143 fmt values typically do not exceed 127, the limit of the value that 144 can be reprsented by an RTP payload type. The ESID allows for values 145 for fmt larger than 127, calculated from the ESID and the RTP payload 146 type in the following way. 148 The value of the ESID is treated as a big-endian integer, which is 149 then shifted left 7 bits and added to the value of the RTP payload 150 type. This integer value is then used as the fmt value in the SDP. 152 5. Examples 154 For an ESID value of 1 and 2 and a Payload Type of 97, the fmt values 155 of (1 << 7) + 97 = 225 and (2 << 7) + 97 = 353 would be used: 157 v=0 158 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 159 s= 160 c=IN IP4 atlanta.example.com 161 t=0 0 162 m=video 10002 RTP/AVP 225 353 163 a=rtpmap:225 VP8/90000 164 a=rtpmap:353 VP8/90000 166 6. Security Considerations 168 TODO 170 7. IANA Considerations 172 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 173 document.] 175 [RFC EDITOR NOTE: Please replace TBD with the assigned SDES 176 identifier value.] 178 This document adds the MID SDES item to the IANA "RTP SDES item 179 types" registry as follows: 181 Value: TBD 182 Abbrev.: ESID 183 Name: Encoded Stream Identification 184 Reference: RFCXXXX 186 8. Acknowledgements 188 9. Normative References 190 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 191 Requirement Levels", BCP 14, RFC 2119, March 1997. 193 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 194 with Session Description Protocol (SDP)", RFC 3264, June 195 2002. 197 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 198 Description Protocol", RFC 4566, July 2006. 200 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 201 Header Extensions", RFC 5285, July 2008. 203 Appendix A. Change log 205 Author's Address 207 Peter Thatcher 208 Google 209 747 6th Ave S 210 Kirkland, WA 98033 211 USA 213 Email: pthatcher@webrtc.org