Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP

Roman Shpount <roman@telurix.com> Thu, 10 May 2012 22:40 UTC

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References: <387F9047F55E8C42850AD6B3A7A03C6C0E23B102@inba-mail01.sonusnet.com> <6F428EFD2B8C2F49A2FB1317291A76C1136029362A@USNAVSXCHMBSA1.ndc.alcatel-lucent.com> <4FA13816.6050003@alvestrand.no> <CAD5OKxsOAeTRdCgj2g4BY8maeG1n9nzCv29g8kaFPVZ4tf8C5w@mail.gmail.com> <4FA15898.1040204@alvestrand.no> <7F2072F1E0DE894DA4B517B93C6A05852C44001329@ESESSCMS0356.eemea.ericsson.se> <CAD5OKxsbTSpMPg30P4DSN6UasCx6na43tpZ5yT2ct6SLMpd9xQ@mail.gmail.com> <7F2072F1E0DE894DA4B517B93C6A05852C4400132C@ESESSCMS0356.eemea.ericsson.se> <6F428EFD2B8C2F49A2FB1317291A76C1136047B753@USNAVSXCHMBSA1.ndc.alcatel-lucent.com> <7F2072F1E0DE894DA4B517B93C6A05852C4400132F@ESESSCMS0356.eemea.ericsson.se> <CAD5OKxuy8_Ras3X-8tcY1qaLRTVJ-z-JuXQaf0NKaRwN_dU18Q@mail.gmail.com> <7F2072F1E0DE894DA4B517B93C6A05852C442AC0DA@ESESSCMS0356.eemea.ericsson.se> <CAD5OKxuv7T6YrEXEeVECKbGtRg4feoRYTgvC57yqWXTBK43ypg@mail.gmail.com> <4FA2B447.7010504@jesup.org> <4FA2E264.4040207@jesup.org> <CAD5OKxuq14_DfSJuFEHq_ZEubbOYt7NFTcXWpLND8ggAr37QhA@mail.gmail.com> <7F2072F1E0DE894DA4B517B93C6A05852C44001339@ESESSCMS0356.eemea.ericsson.se> <CAD5OKxvFYy-9XAE5GG0n58xX2HKRX3o5qkTZ2o6rugakaM77Ew@mail.gmail.com> <7F2072F1E0DE894DA4B517B93C6A05852C4400133A@ESESSCMS0356.eemea.ericsson.se> <CAOJ7v-1Ue=q4MAh0csiDLvRFfMGaJ4vWrDxhir-S-OjSTsymaw@mail.gmail.com> <90DEBA9A-E8D2-4662-9A41-95B361FDAF05@iii.ca> <CAD5OKxvXstf7GOcZc7qdFB6GPvZyzBP8cv+JQcDK6rzbsmA6-Q@mail.gmail.com> <F6B988EE-8847-4AC6-806C-A9B96A075BDB@iii.ca> <CAD5OKxsw+mJ5Ou7_p+nJU55iwuh1xnNrF0YEeST_sBUFWLwLHA@mail.gmail.com> <865D30F8-A632-4D2C-97B4-693854F03210@iii.ca>
Date: Thu, 10 May 2012 18:40:39 -0400
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From: Roman Shpount <roman@telurix.com>
To: Cullen Jennings <fluffy@iii.ca>
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Cc: Randell Jesup <randell-ietf@jesup.org>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
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On Thu, May 10, 2012 at 6:29 PM, Cullen Jennings <fluffy@iii.ca> wrote:

>
> On May 10, 2012, at 3:23 PM, Roman Shpount wrote:
>
> >
> > On Thu, May 10, 2012 at 4:55 PM, Cullen Jennings <fluffy@iii.ca> wrote:
> > > One use case is interop with SIP with parallel forking, reliable
> provisioning responses, UPDATE, and ICE. The big question regarding this
> use case is availability of anything that supports parallel forking,
> reliable provisioning and UPDATE. I actually think ICE makes implementation
> of this use case easier, not harder.
> >
> > So let me try and make sure I understand this uses case. The web browser
> sends some signaling to a server that convert it to a sip call to the
> fork@example.com address. This sends it to theexample.com sip server that
> parallel forks it to two SIP UASs  that are so two phones ring at the same
> time. Now both theses phones are going to negotiate ICE by using reliably
> provisional responses.
> >
> > What products actually do parallel forking like this and return
> provisional reliable responses with ICE. I'm sort of questioning this is a
> common use case. The Nortel, Cisco, Avaya, Siemens etc enterprises PBX
> systems I have seen that support ringing multiple phones at the same time
> don't seem to do this way. They manage to hide the parallel forking with a
> B2BUA model and make it look like sequential forking.
> >
> >
> > Let's say a standard SIP proxy (call it opensips for specificity)
> placing a forked call to two ICE enabled IP phones. Both phones answer with
> 200 OK.
>
> With a standard SIP proxy, only one of the 200 would be sent back to the
> web browser.


AFAIK a standard proxy will forward multiple 200 OK responses (see section
16.7 of RFC 3261). We have the same problem with 183 responses from two
phones anyway.
_____________
Roman Shpount