I agree that this is not the right forum for discussing middlebox buffer management algorithms. I would add that even if the network elements do creep into scope, the host-based congestion control algorithms still have to work with the existing systems found in the wild. In other words, we could suggest that the middleboxes implement [insert your favorite AQM algorithm here]and [insert your pick of ECN, PCN, or maybe even Conex, etc] but the hosts still need to deal with [tail drop, RED, WRED, etc]. Stated another way, the algorithm is going to get a variety of congestion signals. When running on networks with primitive buffer management algorithms, one of those signals is going to be delay. On more modern systems, we can hope that the middleboxes' buffer management algorithms do not introduce persistent delay. So, the RMCAT work will have to consider delay, packet loss and explicit packet markings. In a perfect world, the network will never give us persistent delay - but the world is rarely perfect. Bill VerSteeg -----Original Message----- From: rtp-congestion-bounces@alvestrand.no [mailto:rtp-congestion-bounces@alvestrand.no] On Behalf Of John Leslie Sent: Friday, July 06, 2012 11:38 AM To: Bob Briscoe Cc: rtp-congestion@alvestrand.no; Michael Welzl Subject: Re: [R-C] BoF approved Bob Briscoe <bob.briscoe@bt.com> wrote:
At 11:41 06/07/2012, Michael Welzl wrote:
On 6/26/12 4:05 PM, Wesley Eddy wrote:
The RMCAT BoF was approved to meet at IETF 84 in Vancouver.
From http://trac.tools.ietf.org/bof/trac/ : ] ] Transport ] ] RTP Media Congestion Avoidance Techniques (RMCAT) ] ] Description: WG-forming BoF on RTP congestion control ] Responsible AD: Wesley Eddy ] BoF Chairs: Michael Welzl and Colin Perkins ] Number of people expected to attend: 100 ] Length of session: 2 hours ] Conflicts to avoid: RTCWEB, AVTCORE, MMUSIC, ICCRG, CODEC, TSVWG, TCPM, ] CONEX, PCN, MPTCP, IPPM, CORE ] Webex: not sure ] Meetecho: not sure ] Mailing list: rtp-congestion@alvestrand.no ] I-Ds: http://datatracker.ietf.org/doc/draft-alvestrand-rtcweb-congestion/ ] http://datatracker.ietf.org/doc/draft-jesup-rtp-congestion-reqs/ ] Draft charter: ] http://www.alvestrand.no/pipermail/rtp-congestion/2012-May/000381.html ] Status: APPROVED
When it was discussed by the IESG and IAB, one topic that really needs to be clarified by/within the group is the scope of the mechanisms being developed. For instance, it needs to be more clear what stack the group wants to be chartered to operate on. Whether the group would be doing a mechanism that works for RTP itself, or a new SCTP mechanism will need to be very clear.
I would like to get a grip on exactly *what* really *is* decided regarding the way the stack looks. Which protocol over which protocol(s) for which type of data. ...
Michael,
Recall at the Paris ICCRG I asked the wider question of whether changes to the network are in scope.
This is Transport area, with Wes the expected Responsible AD. That means Network-Layer isn't expected to be in-scope for the WG. I would hope, however, that discussion of potential Network-Layer work which would be helpful would be in-scope for the BoF.
I know those proposing this believe the scope is v definitely e2e protocols only (at least, if not specified down to a specific e2e protocol), but the scope determines very greatly how much of the problem we're going to solve:
* If RTP-only, we don't solve TCP harming RTP, only the other way round (which is fine if that's the scope we want) * If SCTP-only, I'm not sure what we solve? * If we allow network to be in scope, we might be able to address bufferbloat-style issues, or perhaps good policer designs to protect apps from each other.
I expect to do a rant at the Workshop on Congestion Control for Interactive Real-Time Communication July 28th, to the effect that this can't be solved at the Transport Layer only. It looks as if enough of us will be there to discuss Bob's question.
My personal opinion is that this w-g should be trying to solve the problem. And the problem has three halves: * RTP harming elastic * elastic harming RTP * network arbitrating between the two
Clearly the first needs to be in-scope for the WG. IMHO the other two halves need to be discussed at the BoF. ;^) -- John Leslie <john@jlc.net> _______________________________________________ Rtp-congestion mailing list Rtp-congestion@alvestrand.no http://www.alvestrand.no/mailman/listinfo/rtp-congestion