Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sdp-mux-attributes vs draft-ietf-avtcore-rfc5764-mux-fixes
Alan Johnston <alan.b.johnston@gmail.com> Wed, 25 May 2016 20:36 UTC
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References: <CD90C355-FAFD-44F9-8CB0-E40045E31046@nostrum.com> <5745E2F4.8040206@petit-huguenin.org> <9759123A-B014-41AC-95B8-720C50BC9E57@nostrum.com>
Date: Wed, 25 May 2016 13:35:06 -0700
Message-ID: <CAKhHsXG96C141ujTNtKP8D1QEHB2seYnCR67mRYzSqac5fijJg@mail.gmail.com>
From: Alan Johnston <alan.b.johnston@gmail.com>
To: Ben Campbell <ben@nostrum.com>
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Cc: Marc Petit-Huguenin <marc@petit-huguenin.org>, draft-ietf-avtcore-rfc5764-mux-fixes.all@ietf.org, mmusic WG <mmusic@ietf.org>, draft-ietf-mmusic-sdp-mux-attributes.all@ietf.org, "avt@ietf.org WG" <avt@ietf.org>
Subject: Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sdp-mux-attributes vs draft-ietf-avtcore-rfc5764-mux-fixes
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Hi Marc, Changing the packet format for ZRTP is a pretty major change to the protocol... I think the only case where this is an issue would be if both ZRTP and DTLS-SRTP are offered opportunistically (OSRTP), and either ZRTP or DTLS-SRTP arrives before the answer is received. During this window of time, a slightly more complicated algorithm could be used to distinguish ZRTP from DTLS-SRTP, such as checking the 32-bit magic cookie that is present in every ZRTP message. Otherwise, only one of these protocols will be used at a time, so it is not the same as distinguishing either from STUN and RTP, which happens throughout a session. We could put this guidance in a RFC6189bis draft, and the other documents could just defer to that guidance if they support ZRTP in addition to DTLS-SRTP opportunistically. - Alan - On Wed, May 25, 2016 at 10:56 AM, Ben Campbell <ben@nostrum.com> wrote: > Hi Marc, > > That's along the lines that I expected, if the working group chooses this > path. What do others think? > > Thanks! > > Ben. > > On 25 May 2016, at 12:37, Marc Petit-Huguenin wrote: > > As you mention, there are several ways to handle this issue. We leave it >> to the community to decide whether to include zrtp in bundle or not. If we >> were to update the 5764-mux-fix draft, we felt that the cleanest way to >> handle it is in two steps. >> >> One thing to note is that there is no clash/overlap with STUN, so using >> magic cookie to distinguish from STUN is a moot point. The overlap with the >> DTLS range is what we need to avoid. The right thing to do seems to be to >> work on a rfc6189bis draft that would set bit 4 and 5 of the first byte of >> the zrtp message to 0. This way zrtp cannot clash with DTLS. >> >> On the rfc5764-mux-fixes draft, we just change the algorithm to: >> >> +----------------+ >> | [0..3] -+--> forward to STUN >> | | >> | [16..19] -+--> forward to ZRTP >> | | >> packet --> | [20..63] -+--> forward to DTLS >> | | >> | [64..79] -+--> forward to TURN Channel >> | | >> | [128..191] -+--> forward to RTP/RTCP >> +----------------+ >> >> >> Does this seem like a reasonable approach? >> >> >> On 05/24/2016 04:21 PM, Ben Campbell wrote: >> >>> Hi, >>> >>> There appears to be a discrepancy between >>> draft-ietf-mmusic-sdp-mux-attributes and >>> draft-ietf-avtcore-rfc5764-mux-fixes concerning whether zrtp can be used >>> with bundle. >>> >>> mux-attributes puts the zrtp-hash attribute [RFC6189] in the "transport" >>> category, meaning, among other things, that it can be used in a bundle >>> group. However, as the demux rules are currently defined 5764-mux-fixes, >>> zrtp messages cannot actually be demuxed. (If I read things correctly, the >>> first byte of a zrtp message will be 16, which is not in any of the "known >>> ranges" described in 5765 or 5764-mux-fixes, and therefore the message MUST >>> be dropped. >>> >>> That seems to leave the choice of adding zrtp messages to the demux >>> rules in 5764-mux-fixes, or removing the implication that zrtp can be >>> bundled from mux-attributes. >>> >>> Adding rules for demuxing zrtp to 5765-mux-fixes would probably not be >>> hard, but would be non-trivial. RFC 6189 calls for using the magic cookie >>> to distinguish zrtp messages from stun messages. >>> >>> Do people have opinions how to move forward with this? Am I interpreting >>> the conflict correctly?Keep in mind that ZRTP is not a standards-track >>> spec. But at the same time, I'm not sure we want to exclude it from the >>> bundle mechanism. >>> >>> Thanks! >>> >>> Ben. >>> >>> >>> _______________________________________________ >>> Audio/Video Transport Core Maintenance >>> avt@ietf.org >>> https://www.ietf.org/mailman/listinfo/avt >>> >>> > _______________________________________________ > mmusic mailing list > mmusic@ietf.org > https://www.ietf.org/mailman/listinfo/mmusic >
- [AVTCORE] Fwd: [MMUSIC] zrtp: draft-ietf-mmusic-s… Gonzalo Salgueiro (gsalguei)
- [AVTCORE] zrtp: draft-ietf-mmusic-sdp-mux-attribu… Ben Campbell
- Re: [AVTCORE] zrtp: draft-ietf-mmusic-sdp-mux-att… Marc Petit-Huguenin
- Re: [AVTCORE] zrtp: draft-ietf-mmusic-sdp-mux-att… Ben Campbell
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Alan Johnston
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Ben Campbell
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Gonzalo Salgueiro (gsalguei)
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Alan Johnston
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Gonzalo Salgueiro (gsalguei)
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Suhas Nandakumar
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Ben Campbell
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Gonzalo Salgueiro (gsalguei)
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Alan Johnston
- Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sd… Gonzalo Salgueiro (gsalguei)