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Re: I made a PR for changing RtpEncodingParameters.priority to an enum.

From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
Date: Tue, 11 Aug 2015 08:58:13 +0000
To: Harald Alvestrand <harald@alvestrand.no>, "public-webrtc@w3.org" <public-webrtc@w3.org>
Message-ID: <1447FA0C20ED5147A1AA0EF02890A64B342108D0@ESESSMB209.ericsson.se>
On 10/08/15 13:09, Harald Alvestrand wrote:
> Den 24. juli 2015 15:00, skrev Stefan Håkansson LK:
>> On 24/07/15 14:44, Peter Thatcher wrote:
>>> Following the PR from https://github.com/w3c/webrtc-pc/pull/228, I have
>>> changed RtpEncodingParameters.priority to an enum with very-low, low,
>>> medium, and high.
>>>
>>> This is kind of what we decided a long ago about priorities.  But I
>>> forgot about it when I wrote the PR for RtpEncodingParameters.priority
>>> and made it a double.  This is an update to that.
>>>
>>>
>>> Do we still have consensus for using an enum for priority?  Look at the
>>> PR to see how it looks.
>>
>> Which PR is it? Priority seems to be part of #234 and #241.
>>
>> Anyway, I have concerns with the part
>>
>>             <dt>double priority</dt>
>> +          <dd>
>> +            <p>
>> +              Indicates the relative priority of this encoding, across
>> +              all RtpSenders of a given PeerConnection.  When there is
>> +              limited bandwidth available to a PeerConnection, higher
>> +              prioirty encodings will be sent with more bandwidth, and
>> +              lower priority encodings will be sent with less
>> +              bandwidth.
>>
>> in combination with the upcoming "min" and "max" bitrate attributes. How
>> should he UA act if they conflict (e.g. a very high "min" and a low
>> priority)?
>>
>> #228 only points at RTCWEB-TRANSPORT and I think that document only
>> talks about DSCP marking.
>
> Wearing my hat as editor of rtcweb-transport:
>
> Section 4 talks about prioritization.
> Section 4.1 talks about mapping priority to DSCP. This points to
> draft-ietf-dart-dscp-rtp for codepoint assignments.
> Section 4.2 talks about mapping piority to local prioritization. This
> talks about stuff that's congestion-controlled under a single congestion
> controller.
>
> Both chapters assume the 4-level classification of priority at the API -
> section 4 starts with:
>
>     The WebRTC prioritization model is that the application tells the
>     WebRTC implementation about the priority of media and data flows
>     through an API.
>
>     The priority associated with a media or data flow is classified as
>     "normal", "below normal", "high" or "very high".  There are only four
>     priority levels at the API.
>
>     The priority settings affect two pieces of behavior: Packet markings
>     and packet send sequence decisions.  Each is described in its own
>     section below.

This seems well aligned with PR #259 
(https://github.com/w3c/webrtc-pc/pull/259).
Received on Tuesday, 11 August 2015 08:58:42 UTC

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