RTP Payload Format for Society of Motion Picture and Television Engineers (SMPTE) 292M Video
draft-ietf-avt-smpte292-video-08

for the record - here is the RFC Ed note

RFC Editor: please make the following changes before publishing this ID

Section 6, 1st paragraph
OLD:

RFC1889 recommends transmission of RTCP packets every 5 seconds or at a
reduced minimum in seconds of 360 divided by the session bandwidth in
kilobits/second. At 1.485 Gbps the reduced minimum interval computes to
0.2ms or 4028 packets per second.

NEW:

RTCP SHOULD be used as specified in RFC1889[3], which specifies two
limits on the RTCP packet rate: RTCP bandwidth should be limited to 5%
of the data rate, and the minimum for the average of the randomized
intervals between RTCP packets should be 5 seconds.  Considering the
high data rate of this payload format, the minimum interval is the
governing factor in this case.

Section 13, 3rd and 4th paragraphs:
OLD:

[3] H. Schulzrinne, S. Casner, R. Frederick and V. Jacobson, "RTP: A
    Transport Protocol for Real-Time Applications", IETF, Work in
    Progress (draft-ietf-avt-rtp-new-11.txt)

[4] H. Schulzrinee and S. Casner, "RTP Profile for Audio and Video   
    Conferences with Minimal Control", IETF, Work in progress,     
    (draft-ietf-avt-profile-new-12.txt).

NEW:

[3] H. Schulzrinne, S. Casner, R. Frederick and V.  Jacobson, "RTP: A
    Transport Protocol for Real-Time Applications", IETF, January 1996,
    RFC1889.

[4] H. Schulzrinne and S. Casner, "RTP Profile for Audio and
    Video Conferences with Minimal Control", IETF, January 1996, 
    RFC1890.

RFC Editor Note was requested in WG discussion at same time as approval by IESG (2002-Jan-09) [Note from Allison]: 

Section 6, 1st paragraph
OLD:

RFC1889 recommends transmission of RTCP packets every 5 seconds or at a reduced minimum in seconds of 360 divided by the session bandwidth in kilobits/second. At 1.485 Gbps the reduced minimum interval computes to 0.2ms or 4028 packets per second.

NEW:

RTCP SHOULD be used as specified in RFC1889[3], which specifies two limits on the RTCP packet rate: RTCP bandwidth should be limited to 5% of the data rate, and the minimum for the average of the randomized
intervals between RTCP packets should be 5 seconds. Considering the high data rate of this payload format, the minimum interval is the governing factor in this case.

2003-01-12 - response from chair

Glad it passed.  I would like to see the wording tweaked, and it would
be of appropriate size to handle by an RFC Editor noted.  But I don't
have an any broader input from the WG to answer your question.

I would say the answer comes primarily from whether Ladan and Colin
are willing to tweak the wording.  Folks?

2003-01-12 - allison note to chair
Steve,

We in the IESG passed this document on Thursday - would the WG
want to tweak its wording?  I asked Scott (he handled it, I recused,
as an author) to hold for a possible RFC Editor note.

Please advise,

Allison

>
> Date:    Wed, 08 Jan 2003 20:14:30 PST
> To:      AVT WG
> From:    Stephen Casner
> Subject: [AVT] Comment on draft-ietf-avt-smpte292-video-08.txt
>
>
> This comment was triggered by an email from Chuck Harrison, which was
> intern triggerd by one of my questions in the RTP spec/profile series.
> Please take these comments as arriving under the IESG Last Call.
>
> draft-ietf-avt-smpte292-video-08.txt includes the following paragraph
> in its Section 6:
>
>    RFC1889 recommends transmission of RTCP packets every 5 seconds or at a
>    reduced minimum in seconds of 360 divided by the session bandwidth in
>    kilobits/second. At 1.485 Gbps the reduced minimum interval computes to
>    0.2ms or 4028 packets per second.
>
> I have three comments on this:
>
>  - I'm not sure why I did not trip on this before, but RFC 1889 does
>    _not_ recommend transmission of RTCP packets every 5 seconds.  It
>    recommends RTCP transmission based on a scalable timer with 50%
>    randomization and a minimum _average_ interval of 5 seconds.  It
>    is way too tempting already for implementers to put in a fixed
>    5-second timer.  Let's not reinforce that error.
>
>  - RFC 1889 does _not_ include the scaling of the minimum interval.
>    That was added in draft-ietf-avt-rtp-new.  If smpte292-video gets
>    to RFC first, well...
>
>  - Maybe it would appropriate to add another sentence saying that
>    4028 is likely to be excessive for most applications and perhaps
>    suggesting another value.  The rate only needs to be fast enough
>    to track clock skew and to provide enough packets during the
>    23-second octet-count wrap interval to reliably track the wraps.
>
>                                                        -- Steve