Re: [rtcweb] Call for consensus on ICE transport parameter issue (February 15).

Justin Uberti <> Fri, 08 February 2019 19:20 UTC

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From: Justin Uberti <>
Date: Fri, 8 Feb 2019 11:20:25 -0800
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To: Roman Shpount <>
Cc: Ted Hardie <>, RTCWeb IETF <>
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Subject: Re: [rtcweb] Call for consensus on ICE transport parameter issue (February 15).
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On Fri, Feb 8, 2019 at 11:15 AM Roman Shpount <> wrote:

> I am, obviously for this change. As far as I know additional complexity is
> minimal if not completely non-existent. JSEP already requires m= and c=
> line updates based on the default candidate. I do not think there is a lot
> of extra effort in updating the same line based on the same input in two
> places vs one place.
> I would also like to note that:
> 1.  JSEP requires browsers to update the m= line more often then
> mmusic-ice-sip-sdp or RFC 5245. For offers sent during ICE nomination
> process, JSEP asks to set m= and c= line to the last used ICE candidate
> pair. RFC 5245 asks in this case to set this to the default candidate pair,
> which changes a lot less often. It is unclear what is the benefit of
> additional JSEP requirement. It looks like some sort of left over logic
> from re-nomination. This being said, it should not create any interop
> issues and will simply creates additional complexity.

I agree that this should probably be removed from JSEP and codified in
sip-sdp instead; as previously discussed, JSEP doesn't actually use this

> 2. JSEP can produce the answer where default candidate protocol does not
> match the m= line protocol. This is an old RFC 5245 issue and can be fixed
> in the future specification or mmusic-ice-sip-sdp.

This should probably also be fixed in sip-sdp.

> Regards,
> _____________
> Roman Shpount
> On Fri, Feb 8, 2019 at 1:43 PM Ted Hardie <> wrote:
>> Over the the past few weeks, the working group has discussed whether to
>> adopt a change to JSEP which would adjust how the ICE proto line transport
>> parameters are populated in certain mid-session offers where the final
>> candidate is a TCP candidate.  Outside of the extensive working group
>> discussion on the mailing list, participants may also wish to review the
>> follow issue:
>> and the conversations related to these two pull requests:
>> and
>> The chairs believe that there is technical consensus that this proposed
>> change would not materially affect JSEP-only exchanges, since this
>> parameter is ignored in those.
>> The remaining technical issues are:
>> * whether making one of these changes would improve interoperability
>> between WebRTC and non-WebRTC clients which use SIP/SDP.
>> * whether the additional complexity in tracking the use of UDP vs. TCP
>> and populating the parameter accordingly is onerous or unwarranted for
>> WebRTC implementations.
>> After reviewing the discussion to date, the chairs believe that there is
>> rough consensus for the first point, though there is also broad agreement
>> that the benefit of this change is currently theoretical, since no existing
>> WebRTC browser implementation has relevant code.
>> On the second point, the chairs believe that there is no consensus yet
>> demonstrated.  Because we believe that this is in part because the actual
>> proposal has not been entirely clear, and the complexity is therefore
>> somewhat hard to gauge, the chairs wish to make a specific call for
>> consensus.
>> Does the working group approve the change in the following PR:
>> ?
>> Working group participants who have objections to the change are asked to
>> specify whether they believe it has a technical fault, whether they object
>> on the basis of its complexity, or whether they have other issues related
>> to the change they need to raise.
>> The chairs are already aware of the objection of Eric Rescorla on the
>> basis of complexity, and will factor it into the review.
>> Please send comments by February 15th, 2019.
>> regards,
>> Ted Hardie and Sean Turner
>> _______________________________________________
>> rtcweb mailing list
> _______________________________________________
> rtcweb mailing list