Re: [AVTCORE] Spencer Dawkins' Yes on draft-ietf-avtcore-rtp-multi-stream-10: (with COMMENT)

[Magnus Westerlund <[e-mail]>]

Den 2015-12-03 kl. 15:04, skrev Spencer Dawkins at IETF:
> Hi, Magnus,
>
> On Thu, Dec 3, 2015 at 7:02 AM, Magnus Westerlund
> <[e-mail] <mailto:[e-mail]>>
> wrote:
>
>     Hi Spencer,
>
>     Thanks for your comments. See inline
>
>
>     Den 2015-12-03 kl. 04:41, skrev Spencer Dawkins:
>
>         Spencer Dawkins has entered the following ballot position for
>         draft-ietf-avtcore-rtp-multi-stream-10: Yes
>
>         When responding, please keep the subject line intact and reply
>         to all
>         email addresses included in the To and CC lines. (Feel free to
>         cut this
>         introductory paragraph, however.)
>
>
>         Please refer to
>         https://www.ietf.org/iesg/statement/discuss-criteria.html
>         for more information about IESG DISCUSS and COMMENT positions.
>
>
>         The document, along with other ballot positions, can be found here:
>         https://datatracker.ietf.org/doc/draft-ietf-avtcore-rtp-multi-stream/
>
>
>
>         ----------------------------------------------------------------------
>         COMMENT:
>         ----------------------------------------------------------------------
>
>         Thank you for doing this work.
>
>         I have a small number of comments you might consider.
>
>         In this text:
>
>                 Note: The above is chosen to match the TCP initial
>         window of 4
>                 packets, not the larger TCP initial windows for which
>         there is an
>                 ongoing experiment.  The reason for this is a desire to be
>                 conservative, since an RTP endpoint will also in many
>         cases start
>                 sending RTP data packets at the same time as these
>         initial RTCP
>                 packets are sent.
>
>         Not to be pedantic, but it would be more correct to say "TCP maximum
>         initial window of 4 packets". RFC 3390 describes this in
>         TCP-speak as
>
>              Equivalently, the upper bound for the initial window size
>         is based on
>              the MSS, as follows:
>
>                  If (MSS <= 1095 bytes)
>                      then win <= 4 * MSS;
>                  If (1095 bytes < MSS < 2190 bytes)
>                      then win <= 4380;
>                  If (2190 bytes <= MSS)
>                      then win <= 2 * MSS;
>
>         If you end up making changes to this text, providing RFC 3390 as the
>         reference for 4 and RFC 6928 for the experiment would make the
>         reader's
>         job easier.
>
>
>     Yes, we should include the references. So, there are no hard limits
>     on how big the RTCP compound packets can be, but they do need to be
>     within MTU. So for IPv6's 1280 and the Ethernet standard MTU I don't
>     see any issues that this would result in slightly more data than
>     what TCP would send. The difference would be significant when we get
>     to 4k or 9K MTUs. However, I would expect environments where you get
>     this to work, they will not have an issue with sending 4*MTU in data
>     amount.
>
>     Do any on IESG foresee an issue, such that we should redefine the
>     limitation to be in total bytes the initial packets may use, similar
>     to how the initial window is calculated?
>
>
> Oh, heavens, don't do that!

I was simply asking, I tried to convey that I don't see any real issue 
here.

>
> My point was only that that the standard TCP initial window isn't always
> 4 segments, and I was hoping to make that clearer by saying "maximum
> initial window".
>
> People spilled enough blood on the 2, or 3, or 4 discussion leading up
> to RFC 3390, that I'd like to avoid confusing new transport folk now.

Sure, I have no problem adding "maximum" and the references to this note.


Cheers

Magnus Westerlund

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