Re: [rtcweb] Some language on "prioritization"

[Harald Alvestrand <[e-mail]>]

On 03/31/2014 07:42 PM, Michael Tuexen wrote:
> On 31 Mar 2014, at 19:38, Martin Thomson <[e-mail]> wrote:
>
>> On 31 March 2014 10:08, Harald Alvestrand <[e-mail]> wrote:
>>> -- TODO: Specify a relative priority scheme that makes sense with SCTP,
>>> with an appropriate reference. [draft-ietf-tsvwg-sctp-prpolicies]
>>> specifies a priority policy, but it's about discarding packets, not
>>> deciding which packets to send first, and it also makes it impossible to
>>> specify time-bounded retransmission. --
>>
>> Why would SCTP need special treatment?  I can understand if there are
>> particular time-sensitive control messages that need to be given
>> higher priority, but this is all time-sensitive.
> A single transport connection (in this case an SCTP association) can
> only use a single DSCP. So it would be OK to use the same priority for
> all data channels, but things get complicated when when some data channels
> would have different priorities requiring different DSCP markings.

The SCTP protocol machine will, at some given moment in time, have
packets in its send buffers that belong to multiple data channels. Only
one of them can go on the wire first.

Which packet does it choose to send first, and why?

That's the question I'm looking for an answer to.

If the answer has an RFC number, chapter and section, I'd be very happy.
If it doesn't - perhaps we have to invent one.
Or say that it's "implementation dependent".