Re: [rtcweb] Prioritization

Martin Thomson <martin.thomson@gmail.com> Wed, 30 April 2014 21:23 UTC

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Date: Wed, 30 Apr 2014 14:23:26 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: "Cullen Jennings (fluffy)" <fluffy@cisco.com>
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Subject: Re: [rtcweb] Prioritization
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On 30 April 2014 14:09, Cullen Jennings (fluffy) <fluffy@cisco.com> wrote:
> On Apr 25, 2014, at 11:03 AM, Matthew Kaufman (SKYPE) <matthew.kaufman@skype.net> wrote:
>
>> If a "lower priority" packet is dispatched before a "higher priority" packet in order to "prevent starvation", then what does "higher priority" mean?
>
> I think the labels reflect what "might" happen on average and not for any particular packet.

I think that Matthew was referring to the part where the browser is
involved.  That is, the bit where, when presented with the option to
send just one packet from buckets A through D, how does it choose from
those buckets.

The implication was that if A is more important than B, then if A
wants to send, it gets to send.  Period.  The "prevents starvation"
view of the world says that work is shared between A-D, with
increasingly large proportions of the available capacity given to
higher priority streams.  The problem with both these models is that
they are crap in various ways.  In one, you get cases where lower
priority stuff never happens, even if that isn't what you wanted; in
another, lower priority stuff can get resources, and that wasn't what
you wanted.

The DSCP markings and how they might interact with this are just an
additional layer of uncertainty, primarily.