Re: [MMUSIC] SCTP question: Where does it multiplex?

Matthew Kaufman <> Tue, 11 December 2012 23:12 UTC

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Subject: Re: [MMUSIC] SCTP question: Where does it multiplex?
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On 12/11/2012 10:53 AM, Dan Wing wrote:

> Sending bulk data (SCTP) and interactive audio/video over the same port
> will break prioritization of the audio/video flow above the bulk data.

In Lyon, we made the assertion that a browser network stack MUST be able 
to maintain a common congestion state that is shared between the various 
streams (1 or more RTP, at least 1 SCTP, etc.) and which is used to 
prioritize the dispatching of packets onto the network appropriate 
across at least 3 (I recommended 4) priority levels. This is *in 
addition* to the idea that these 3 (or 4) levels are also diffserv 
marked in a way that the network can apply different treatments to them.

(I recommended at least 4 levels to cover 
data-that-is-more-important-than-anything, audio, video, and 

>> I also understand why multiple independent non-
>> HOL blocking streams within SCTP are useful for applications. But I
>> don't yet understand the additional benefit of multiple parallel SCTP
>> associations. No doubt it can be technically done, but to what purposes?
> One example:  transferring a big file while, at the same time, doing
> screen sharing or an instant message chat.

The fact that SCTP also suffers from a head-of-line blocking issue 
because its flow control is per-association not per-flow (ref: ) does 
suggest that until that is resolved one might want to use >1 SCTP 
association between peers as well.

Matthew Kaufman