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

[Spencer Dawkins at IETF <[e-mail]>]

Hi, Magnus,

On Thu, Dec 3, 2015 at 8:22 AM, Magnus Westerlund <
[e-mail]> wrote:

> 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.


You were doing the right thing. I wasn't clear enough in my point.


>
>
>
>> 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.


Thanks!

Spencer


>
>
>
> Cheers
>
> Magnus Westerlund
>
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