Just to close this off (comments inline)
Tiphon is not expressing any position on this stuff, the meeting happened to be during the ETSI session but has nothing to do with it.
What was agreed was correctly expressed by Gur (extracted from the very bottom of previous posting) and Matt is right, we made some progress
I am suggesting that:
We acknowledge the limitation of SDP and find a solution that works, this is where people will write contributions. Whatever we choose is in any-case no longer compliant SDP.
we change the capabilities descriptors (that we choose based on the previous point...) to be "by reference".
that we clarify the internal consistency model.
The below point 1, 3, 5 were discussed and nothing was decided on how to solve the issues: actually it was not mentioned whether SDP is flawed or not, simply it was noted that MEGACO gateways need to interoperate with existing legacy H.323 gateway and endpoints and there is a need to make this working.
Capabilities By Reference vs By Value was also mentioned and a more general consensus will be searched.
Point 2 and 6: these seems more a proposal for addressing some issues; these are not an output of that conversation
From: H323MAIL H323MAIL@VOCALTEC.COM Subject: H.GCP / Megacop capabilities desctriptors issue Comments: To: ITU-SG16@mailbag.cps.intel.com, MEGACO@STANDARDS.NORTELNETWORKS.COM To: ITU-SG16@mailbag.cps.intel.com
Dear GCPers/MEGACOPers
There has been some discussion lately on the suitability of standard SDP for expressing the capabilities of MGs. At the TIPHON meeting in Bangkok (some of us <are> having fun) we held an informal meeting with participants from Telcordia, VocalTec, Siemens, Ascend, Motorola, Dialogic and Lucent (forgive me if I forgot someone).
There was general agreement (by which I do NOT mean consensus...) that the use of SDP in Megacop as it currently stands is a problem:
- SDP cannot express inartistic hardware limitations, such as mutually
exclusive sets of capabilities (e.g. "I can do 24 x GSM and 24 x 723 but not at the same time").
- This has two implications:
either the MG cannot express these limitations, which means that it will reject many commands from the MGC, as the MGC is unaware of the limitations (we called it "reject floods").
or the MG will have to be designed (with extra DSP/memory for example) to not have any limitations that cannot be expressed using SDP.
If you build hardware, this is immediately obvious.
- Interoperability between decomposed GWs and simple 323 endpoints will
be effected, as many calls will fail due to capabilities (and current resource use implications) not being correctly represented to the call signalling layer.
- That the current method of expressing capabilities (regardless of SDP)
is "by Value" and should be "by Reference", where:
a master-set of capabilites is represented at the root level, and references to it are used when issueing commands;
leaf-nodes only contain logical references: (e.g. "I am a T1 line, I can do 24 x Cap-1 OR 22 x Cap-2")
- That the discussion of "SDP Vs. H.245" is inherently flawed, as:
- SDP is only capabilities descriptors, and H.245 is also multiple sets
of procedures (master/slave, caps-exchange, OLCs, conferencing control).
The issue is whether we should be using H.245 CAPABILITIES DESCRIPTORS irrelevant of packetizarion, not the actual procedures of H.245.
that talking about H.245 does not immediately mean ASN.1 PER.
- That the internal model is not consistent (this may have been
corrected in the latest draft from Brian) - by this I mean that
The MGC knows what the state of it's MG is because it is the only entity that can change it (one-to-one relationship); and
if the state of the MG changed NOT DUE TO A COMMAND FROM THE MGC, the MG must report this to the MGC.
This handles failures (where some trunk-group went out of service) and when the resources of multiple logical MGs are an expression of on physical MG.
______________________________________________________ Massimo Lucchina TEL: +33 1 69185269 16 av. du Quebec, Villebon BP FAX: +33 1 69288326 91961 Les Ulis - France GSM: +33 6 07675242