RTP Payload Format for Generic Forward Error Correction
Draft of message to be sent after approval:
From: The IESG <email@example.com> To: IETF-Announce <firstname.lastname@example.org> Cc: Internet Architecture Board <email@example.com>, RFC Editor <firstname.lastname@example.org>, avt mailing list <email@example.com>, avt chair <firstname.lastname@example.org> Subject: Protocol Action: 'RTP Payload Format for Generic Forward Error Correction' to Proposed Standard The IESG has approved the following document: - 'RTP Payload Format for Generic Forward Error Correction ' <draft-ietf-avt-ulp-24.txt> as a Proposed Standard This document is the product of the Audio/Video Transport Working Group. The IESG contact persons are Cullen Jennings and Jon Peterson. A URL of this Internet-Draft is: http://www.ietf.org/internet-drafts/draft-ietf-avt-ulp-24.txt
Technical Summary This document specifies a payload format for generic Forward Error Correction (FEC) for media data encapsulated in RTP. It is based on the exclusive-or (parity) operation. The payload format described in this draft allows end systems to apply protection using various protection lengths and levels, in addition to using various protection group sizes to adapt to different media and channel characteristic. It enables complete recovery of the protected packets or partial recovery of the critical parts of the payload depending on the packet loss situation. This scheme is completely compatible with non-FEC capable hosts, so the receivers in a multicast group that do not implement FEC can still work by simply ignoring the protection data. This specification obsoletes RFC 2733 and RFC 3009. The FEC specified in this document is not backward compatible with RFC 2733 and RFC 3009. Working Group Summary This document has been under discussion in the AVT working group since the 48th IETF meeting, having been brought to AVT along with a competing draft (draft-lnt-avt-uxp-00.txt) from the ITU-T SG16. Considering their relative merits, AVT eventually decided to adopt both drafts, this draft being simpler and conceptually backwards compatible with RFC 2733, the UXP work being more complex (based on Reed Solomon coding, rather than simple parity coding) but with potentially better performance in some scenarios. Work on the UXP draft was abandoned in 2004, and the ULP draft progressed to completion. More recently, there has been some discussion of the merits of the ULP work, compared to the schemes employed by 3GPP, and the ongoing work in FECFRAME. We believe the FECFRAME proposals will likely form the basis of future FEC work for RTP. Despite this, we believe it necessary to publish the ULP draft all the same, since it contains an important bug fix to RFC 2733, and since the layered extensions can potentially offer improved performance in a manner that is conceptually compatible with to RFC 2733. Document Quality Media type review on the -14 took place starting in December 2005, with no objection (there have been no changes in the draft that would change that consensus since then). Jonathan Rosenberg and Mark Watson provided extensive last call comments and review. Personnel Colin Perkins is the document shepherd. Cullen Jennings is the responsible AD. David McGrew and Eric Rescorla review the interaction of SRTP encryption and FEC.