Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sdp-mux-attributes vs draft-ietf-avtcore-rfc5764-mux-fixes
"Ben Campbell" <ben@nostrum.com> Thu, 26 May 2016 03:50 UTC
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From: Ben Campbell <ben@nostrum.com>
To: Suhas Nandakumar <suhasietf@gmail.com>
Date: Wed, 25 May 2016 22:50:15 -0500
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References: <CD90C355-FAFD-44F9-8CB0-E40045E31046@nostrum.com> <5745E2F4.8040206@petit-huguenin.org> <9759123A-B014-41AC-95B8-720C50BC9E57@nostrum.com> <CAKhHsXG96C141ujTNtKP8D1QEHB2seYnCR67mRYzSqac5fijJg@mail.gmail.com> <80563BED-ADDE-4C2B-8B4E-DF1C8F3E3FA5@cisco.com> <CAKhHsXGDneqTTaZ0tkw3WxsCPStLuMWGBSDHnarc+4YA-t-tyA@mail.gmail.com> <CCF13C88-3C10-4E73-88A5-B70BA1C15A20@cisco.com> <CAMRcRGTRkM8wksX8jHBwa1+kT_JSN9x=HtpV81+LcwdvsdcWNg@mail.gmail.com>
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Cc: mmusic WG <mmusic@ietf.org>, Marc Petit-Huguenin <marc@petit-huguenin.org>, "avt@ietf.org WG" <avt@ietf.org>, "draft-ietf-mmusic-sdp-mux-attributes.all@ietf.org" <draft-ietf-mmusic-sdp-mux-attributes.all@ietf.org>, "draft-ietf-avtcore-rfc5764-mux-fixes.all@ietf.org" <draft-ietf-avtcore-rfc5764-mux-fixes.all@ietf.org>
Subject: Re: [AVTCORE] [MMUSIC] zrtp: draft-ietf-mmusic-sdp-mux-attributes vs draft-ietf-avtcore-rfc5764-mux-fixes
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Since I'm the one who originally complained about TRANSPORT I should probably respond :-) I agree TRANSPORT makes sense if people agree to the changes in mux-fixes. Ben. On 25 May 2016, at 22:09, Suhas Nandakumar wrote: > Thanks Ben, Alan , Gonzalo & Marc for driving these discussions. > > > Just getting back to the original question that Ben had on the > mux-cateory > for ZRTP - Do we all agree that with the changes to rfc5764-mux-fixes > the > category TRANSPORT makes sense ? Since that helps clarify demuxing ... > > Thanks > Suhas > > On Wed, May 25, 2016 at 8:05 PM, Gonzalo Salgueiro (gsalguei) < > gsalguei@cisco.com> wrote: > >> OK, cool Thanks, Alan. Once we get consensus from the WG(s) that >> this is >> the best way forward we will make this change to >> draft-ietf-avtcore-rfc5764-mux-fixes. >> >> Cheers, >> >> Gonzalo >> >>> On May 25, 2016, at 8:01 PM, Alan Johnston >>> <alan.b.johnston@gmail.com> >> wrote: >>> >>> Hi Gonzalo, >>> >>> Thanks for the clarification - I had it backwards in my head. >>> Existing >> ZRTP implementations will be compliant to the proposal, and we can >> constrain those bits to 0 in the 6189bis draft to lock it down. >>> >>> So I am OK with this proposal. >>> >>> - Alan - >>> >>> On Wed, May 25, 2016 at 1:56 PM, Gonzalo Salgueiro (gsalguei) < >> gsalguei@cisco.com> wrote: >>> Hi Alan - >>> >>> One of the reasons we made the suggestion was because (in our >> estimation) it did not have a major impact to the ZRTP packet format. >> Currently the packet format is: >>> >>> >>> 0 1 2 3 >>> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> |0 0 0 1|Not Used (set to zero) | Sequence Number | >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> | Magic Cookie 'ZRTP' (0x5a525450) | >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> | Source Identifier | >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> | | >>> | ZRTP Message (length depends on Message Type) | >>> | . . . | >>> | | >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> | CRC (1 word) | >>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >>> >>> >>> Our proposal was to set bits 4 and 5 to zero, which is currently >>> what >> the protocol calls for and should implicitly make all existing >> implementations compliant. All we are proposing is is to take bits 4 >> and 5 >> out of the “Not Used” range and leave them fixed to the value >> that current >> implementations use. Does this make sense? >>> >>> In any case, I’d like to try and understand what impact this has >>> to the >> current rfc5764-mux-fix text. Is it as simple as explicitly >> reserving >> values 16 - 19 for ZRTP? Or did you have something else in mind? If >> you >> can make specific text suggestions that will simplify things. >>> >>> Thanks, >>> >>> Gonzalo >>> >>> >>> >>> >>> >>>> On May 25, 2016, at 1:35 PM, Alan Johnston >>>> <alan.b.johnston@gmail.com> >> wrote: >>>> >>>> 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 >>>> >>> >>> >> >> _______________________________________________ >> 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)