Re: [rtcweb] [MMUSIC] Default proto transport in JSEP

Justin Uberti <> Mon, 19 November 2018 18:35 UTC

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From: Justin Uberti <>
Date: Mon, 19 Nov 2018 10:34:51 -0800
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To: Roman Shpount <>
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Subject: Re: [rtcweb] [MMUSIC] Default proto transport in JSEP
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IIRC, one reason JSEP chose the behavior described is because
5245-compliant implementations would declare an ICE mismatch if we used a
bogus address/port in the c=/m= lines. Is this not a problem?

On Mon, Nov 19, 2018 at 10:28 AM Roman Shpount <> wrote:

> Hi All,
> The current language in JSEP makes it incompatible with any ICE
> implementation, either existing or the future ones compliant with
> ice-sip-sdp draft. You can, of course, overwrite ice-sip-sdp, but this will
> mean JSEP will be a completely incompatible system..
> The problem is that JSEP proposes to use UDP protocol in the m= line and
> at the same time update address and port to the currently selected
> candidate. Based on ice-sip-sdp, if protocol of the current selected
> candidate does not match protocol in the m= line, this will mean either ICE
> mismatch or additional candidate with protocol, address, and port form m=
> and c= line.
> Second, ice-sip-sdp treats SDP during ICE restart, when multiple
> candidates are present different from SDP when ICE is not restarted (single
> candidate). According to ice-sip-sdp, when only a single candidate is
> present, this candidate protocol, address and port are set in m= and c=
> line. JSEP proposes to put original UDP protocol and address and port from
> the single candidate.
> To be specific, it is not the fact that protocol in m= line is not updated
> is an issue. It is that protocol in not updated but address and port in m=
> and c= line are updated. In the ice-sip-sdp draft there is a solution for
> this issue -- set address to IN IP4 and port to 9. This is
> specifically supposed to be ignored and not cause the ICE mismatch or extra
> candidates. If JSEP wants to overwrite ice-sip-sdp, it can specify that m-
> line protocol should always be set to UDP based protocol, c= line address
> should be set to   IN IP4 and m= line port set to 9. In case of an
> ICE only system where c= and m= line address information is irrelevant,
> this makes implementation simpler since m= and c= line address information
> can stay constant for the duration of the session.
> Regards,
> _____________
> Roman Shpount
> _______________________________________________
> mmusic mailing list