Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00
Justin Uberti <juberti@google.com> Tue, 01 November 2011 19:39 UTC
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From: Justin Uberti <juberti@google.com>
Date: Tue, 01 Nov 2011 15:37:05 -0400
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To: Michael Tüxen <Michael.Tuexen@lurchi.franken.de>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>, Randall Stewart <rrs@lakerest.net>
Subject: Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00
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I think we want one DTLS session for each transport. If we have independent RTP sessions, we have N transports, and N DTLS sessions. If we multiplex RTP/SCTP sessions, we have a single transport, and the same DTLS session is used to protect SCTP traffic, as well as to get keys for SRTP traffic. On Tue, Nov 1, 2011 at 11:19 AM, Michael Tüxen < Michael.Tuexen@lurchi.franken.de> wrote: > On Nov 1, 2011, at 3:10 PM, Magnus Westerlund wrote: > > > On 2011-10-26 22:45, Michael Tüxen wrote: > >> > >> On Oct 26, 2011, at 10:28 PM, Hadriel Kaplan wrote: > > > >>> But rather this: > >>> > >>> +------+ +------+ > >>> |WEBAPP| |WEBAPP| > >>> +------+------+------+ +------+------+------+ > >>> | DTLS | Audio| Video| | SCTP | Audio| Video| > >>> +---------------------------+ +---------------------------+ > >>> | STUN | SCTP |S/RTP |S/RTP | | STUN | DTLS |S/RTP |S/RTP | > >>> +---------------------------+ +---------------------------+ > >>> | Mux/Demux | | Mux/Demux | > >>> +---------------------------+ +---------------------------+ > >>> | UDP | | UDP | > >>> +---------------------------+ +---------------------------+ > >>> > >>> [Note: "S/RTP" = SRTP/SRTCP or RTP/RTCP, "Mux/Demux" = tiny logic to > mux/demux] > >>> > >>> Because the audio/video streams may be using the same UDP port, right? > >>> > >>> And the two "S/RTP" boxes may be just one box depending on how the > MMUSIC multiplexing decision turns out. > >>> > >>> So if we want to choose the left one, because we expect/want that > someday the Operating System provides a SCTP/UDP stack in the kernel, and I > think we do, could it do so while demuxing and letting STUN, RTP, and DTLS > go up to the app layer? (i.e., given a socket/BIO/FD model) I have no > idea about such things... just asking. > >> This is not possible today. The demultiplexing seems to be specific to > this scenario. > >> Not sure it fits. For demuxing you use the first byte to distinguish > STUN from DTLS and SRTP. > >> The first byte us the high order byte of the source port. Once could > require > >> SCTP to use source ports with the high order byte > 192. That might > work. > >> However, you would need to get the Mux/Demux into the kernel. Could be > done > >> using a socket option. But I'm not sure it really fits. Maybe Randy has > an > >> opinion. > >> > > > > Michael, > > > > I think one of the reasons there is discussion of use land > > implementations of SCTP is so that you can do the above stack diagrams > > with SCTP above UDP that is being shared for several purposes. > > > > I would also like to correct Hadriel's picture slightly: > > > >>> +------+ +------+ > >>> |WEBAPP| |WEBAPP| > >>> +------+------+------+ +------+------+------+ > >>> | DTLS |Audio & Video| | SCTP |Audio & Video| > >>> +---------------------------+ +---------------------------+ > >>> | STUN | SCTP | DTLS-SRTP | | STUN | DTLS | DTLS-SRTP | > >>> +---------------------------+ +---------------------------+ > >>> | Mux/Demux | | Mux/Demux | > >>> +---------------------------+ +---------------------------+ > >>> | UDP | | UDP | > >>> +---------------------------+ +---------------------------+ > > > > I think the above indicating that the common RTP session, potentially > > being a DTLS-SRTP keyed RTP session that can co-exist on the same UDP > flow. > > > > To make the left one work, I think one has to have a source port where > > the first byte value is 192-255 as the de-multiplexing table from > > section 5.1.2 of RFC 5764 shows these to be the only available. > > > > Thus I think the options are: > > > > A. Left figure above. (source port must be in 49152-65535) > > > > B. Right figure above > > > > C. SCTP in its own UDP flow plus one UDP flow for each RTP session. > > > > If we would pick SCTP then I think we must have either A+C or B+C > working. > And you want one DTLS connection for key derivation of SRTP and a > separate one for SCTP? Or must they be the same? > > Best regards > Michael > > > > cheers > > > > Magnus Westerlund > > > > ---------------------------------------------------------------------- > > Multimedia Technologies, Ericsson Research EAB/TVM > > ---------------------------------------------------------------------- > > Ericsson AB | Phone +46 10 7148287 > > Färögatan 6 | Mobile +46 73 0949079 > > SE-164 80 Stockholm, Sweden| mailto: magnus.westerlund@ericsson.com > > ---------------------------------------------------------------------- > > > > > > _______________________________________________ > rtcweb mailing list > rtcweb@ietf.org > https://www.ietf.org/mailman/listinfo/rtcweb >
- [rtcweb] Layers in draft-jesup-rtcweb-data-00 Hadriel Kaplan
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Christer Holmberg
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Michael Tüxen
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Magnus Westerlund
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Michael Tüxen
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Justin Uberti
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Michael Tüxen
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Magnus Westerlund
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Eric Rescorla
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Wolfgang Beck
- Re: [rtcweb] Layers in draft-jesup-rtcweb-data-00 Magnus Westerlund