[Bloat] [e2e] [aqm] What is a good burst? -- AQM evaluation guidelines

Naeem Khademi naeem.khademi at gmail.com
Mon Dec 16 09:05:56 EST 2013

and to clarify more about what else was discussed, it seems to me some of
us tend to correspond and relate the notion of "good queue" vs. "bad queue"
used by KN+VJ ACM queue paper to my question on "good bursts". While they
likely to be correlated (I have no argument on this now), the notion of
"good burst" goes beyond the "good queue" defined in that paper. Based on
their definition a good queue is a queue that minimizes the standing queue
(or gets rid of it entirely) while allowing a certain amount of (sub-RTT?
typical 100 ms) bursts while avoiding the link to get under-utilized. That
notion (again, I have no argument on its correctness for now) is different
from my question on "good bursts" which means that: once we manage to get
rid of the standing queue, what types/sizes of bursts I should let the AQM
X to protect/handle?


On Mon, Dec 16, 2013 at 2:47 PM, Naeem Khademi <naeem.khademi at gmail.com>wrote:

> Bob, Fred and all
> I'll copy/paste the question here again: "what is a good burst (size)
> that AQMs should allow?" and/or "how an AQM can have a notion of the right
> burst size?"
> So, obviously, as Bob mentioned, I'm concerned about what AQMs should or
> shouldn't do. The mission of dealing with packet bursts in addition to the
> task of keeping the standing queue very low or minimal is part of an "AQM
> evaluation criteria" I envision. While I do agree with all Fred's remarks,
> I'm more concerned to have an answer for this, for where AQMs might get
> deployed.
> An example: when designing my AQM X should I care about 64K TSO-generated
> bursts to safely pass without dropping or not?  Does the answer (whatever
> it is) also apply to the burst sizes typical of multimedia traffic, etc.?
> if the answer is "yes", should an AQM design be actively aware of what
> application layer does in terms of sending bursty traffic or not? and to
> what extent if yes?
> Regards,
> Naeem
> On Mon, Dec 16, 2013 at 8:34 AM, Fred Baker (fred) <fred at cisco.com> wrote:
>> On Dec 15, 2013, at 2:57 PM, Bob Briscoe <bob.briscoe at bt.com>
>>  wrote:
>> > Fred,
>> >
>> > Jonathan Morton, Michael Scharf & I took Naeem's question to mean "What
>> should an AQM assume the size of a good burst is?" whereas I think you and
>> David C-B took the question to mean "What should an end-system take the
>> size of a good burst to be?".
>> I can't comment on what he means. I took the question as "what should a
>> system that is in receipt of what it might consider a 'burst', and more
>> especially a 'good burst', to be?"
>> I don't know that a sending transport (which is to be distinguished from
>> the queueing arrangement in that same system) or a receiving system *has* a
>> definition of a "good" or "bad" burst. The one is sending data, which in
>> the context of y two examples might be a good or bad idea, and the other is
>> receiving it. From the receiver's perspective, the data either arrived or
>> it didn't; if it arrived, there is no real argument for not delivering it
>> to its application...
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