Re: [Simple] COMEDIA vs MSRP Relays: Shared Connections

["Christer Holmberg" <christer.holmberg at ericsson.com>]

Hi, 

>>>I'm not sure I follow you - Comedia has a "connection:existing"  
>>>attribute setting to re-use the same connection (e.g., in a new 
>>>offer).  Or do you mean of two separate media m= lines?
>>
>>You are right of course. Brain fart on my part. However, the draft 
>>should probably mention how to apply this--the only reference I see to

>>connection:existing is in the ICE section.
>
>Wait, I remember why I brought this up--if a peer is behind an MSRP  
>relay, how is it to know whether a reuseable connection already exists

>downstream of that relay?

Even if it knows, how would it tell the relay whether to actually reuse
that connection? I guess that would require some new information
element.

Note, however, that according to section 4.1.3, connection re-use is not
used for initial offer/answers, only for re-negotiations.

In any case, I can add something about this to my presentation.

Regards,

Christer


>>> -----Original Message-----
>>> From: simple-bounces at ietf.org [mailto:simple-bounces at ietf.org] On  
>>> Behalf
>>> Of Ben Campbell
>>>
>>> How does the COMEDIA negotiation interact with the TCP-connection-
>>> sharing features of MSRP? We negotiate sessions in the SDP offer/
>>> answer, not connections per se. COMEDIA implicitly assumes a one-to-
>>> one correspondence between these, but MSRP explicitly allows  
>>> multiple
>>> sessions to use the same TCP connection.
>>>
>>> I can see two approaches. One would be that the COMEDIA attributes  
>>> are
>>> only relevant if you have to create a new connection. If a reusable
>>> connection already exists, you just use it. Alternatively, we could
>>> state that a connection is only reuseable if it's direction matches
>>> the COMEDIA attributes, and if devices wanted to reuse an existing
>>> connection, they would either omit COMEDIA entirely, or choose  
>>> COMEDIA
>>> attributes that match the connection.
>>>
>>> Neither of those approaches seems obviously wrong to me. I suspect
>>> there may be some traps here, though--we should analyze this pretty
>>> closely.
>>>
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