Subject: [AVTCORE] [Technical Errata Reported] RFC4585 (3313)

From: RFC Errata System <[email-masked]>
Date: Sat, 11 Aug 2012 13:57:08 -0700 (PDT)

The following errata report has been submitted for RFC4585,
"Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=4585&eid=3313

--------------------------------------
Type: Technical
Reported by: Mo Zanaty <[email-masked]>

Section: 4.2

Original Text
-------------
      rtcp-fb-ack-param  = SP "rpsi"
                         / SP "app" [SP byte-string]
                         / SP token [SP byte-string]
                         / ; empty

Corrected Text
--------------
      rtcp-fb-ack-param  = SP "rpsi"
                         / SP "app" [SP byte-string]
                         / SP token [SP byte-string]

Notes
-----
RFC 4585 defines and allows generic NACK (with no further parameters) but not generic ACK (which always requires further parameters). Section 4.2 says:
...
      Parameters MUST be provided to further distinguish different types
      of positive acknowledgement feedback.
...
      The feedback type "nack", without parameters, indicates use of the
      Generic NACK feedback format as defined in Section 6.2.1.
...
The ABNF incorrectly allows nothing after "ack", implying that generic ACK is valid. Even the approved errata, which replaces the invalid empty alternate with optional [], still allows nothing after "ack". Note that recent interest in RTP congestion control (e.g. RMCAT BOF) may lead to defining a standard ACK.

Instructions:
-------------
This errata is currently posted as "Reported". If necessary, please
use "Reply All" to discuss whether it should be verified or
rejected. When a decision is reached, the verifying party (IESG)
can log in to change the status and edit the report, if necessary. 

--------------------------------------
RFC4585 (draft-ietf-avt-rtcp-feedback-11)
--------------------------------------
Title               : Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)
Publication Date    : July 2006
Author(s)           : J. Ott, S. Wenger, N. Sato, C. Burmeister, J. Rey
Category            : PROPOSED STANDARD
Source              : Audio/Video Transport
Area                : Real-time Applications and Infrastructure
Stream              : IETF
Verifying Party     : IESG