[R-C] [Iccrg] Re: Timely reaction time (Re: Comments on draft-alvestrand-rtcweb-congestion-01)

Stefan Holmer stefan at webrtc.org
Mon Apr 2 14:04:12 CEST 2012


I think what you are requesting should be possible with the requirement
that the REMB feedback messages should be sent periodically. If none is
received within some threshold the sender have to start backing off. REMB
are typically sent periodically anyway to be able to probe the channel.

/Stefan

On Mon, Apr 2, 2012 at 7:44 AM, Michael Welzl <michawe at ifi.uio.no> wrote:

> Argh, yes, I guess this one letter was the cause of a misunderstanding...
> Thanks!
>
> Sent from my iPod
>
> On Apr 1, 2012, at 23:56, Lachlan Andrew <lachlan.andrew at gmail.com> wrote:
>
>  Greetings Michael,
>>
>> Are you saying you need an emergency "brake" (i.e., slowing down)
>> rather than emergency "break" (i.e., termination, with or without a
>> restart later)?
>>
>> Cheers,
>> Lachlan
>>
>>
>> On 30 March 2012 21:17, Michael Welzl <michawe at ifi.uio.no> wrote:
>>
>>>
>>> On Mar 30, 2012, at 10:33 AM, Harald Alvestrand wrote:
>>>
>>>  On 03/29/2012 01:55 PM, Michael Welzl wrote:
>>>>
>>>>>
>>>>>
>>>>>
>>>>>  Section 4: par 3, "This algorithm is run every time a receive report
>>>>>> arrives..." => so in case of severe congestion, when nothing else
>>>>>> arrives,
>>>>>> this algorithm waits for 2 * t_max_fb_interval... so can we rely on
>>>>>> the
>>>>>> mechanism to react to this congestion after roughly an RTO or not?
>>>>>> (sounds
>>>>>> like not)  Is that bad?  (I guess)
>>>>>>
>>>>>> There is a need for some emergency break mechanism if no feedback gets
>>>>>> through.
>>>>>>
>>>>>
>>>>>
>>>>> I totally agree - what I meant is, it isn't clear to me if that
>>>>> emergency
>>>>> break is activated in time or too late. It should be in time (i.e.
>>>>> after
>>>>> roughly an RTO).
>>>>>
>>>>
>>>> This seems to be a subject that should be discussed in the context of
>>>> the
>>>> circuit-breakers draft: What kind of response time is appropriate for
>>>> such a
>>>> mechanism, and why?
>>>>
>>>
>>>
>>> I think not: we're talking about two kinds of situations here. The
>>> context
>>> here is: there was congestion, we should react to it within an RTO (and
>>> have
>>> an "emergency break" to always do that - but maybe that term was
>>> misleading). The circuit-breakers draft is about a much more serious
>>> condition (such as persistent congestion), warranting a much more serious
>>> reaction (terminating the connection).
>>>
>>> Cheers,
>>> Michael
>>>
>>
>>
>>
>> --
>> Lachlan Andrew  Centre for Advanced Internet Architectures (CAIA)
>> Swinburne University of Technology, Melbourne, Australia
>> <http://caia.swin.edu.au/cv/**landrew<http://caia.swin.edu.au/cv/landrew>
>> >
>> Ph +61 3 9214 4837
>>
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