Re: [MMUSIC] SDPCapNeg : 2nd o/a via UPDATE?

[Bob Gilman <bob_gilman at comcast.net>]

Zhengrong-
The media capabilities extensions can't be used to avoid a second
exchange in the case where a media stream is reconfigured, e.g., from
inactive to sendrecv, or when confirmation of requested conditions
is required in both directions.
I apologize for not qualifying my earlier statement.
-Bob
-------------------------------------------------------------
Bob Gilman        bob_gilman at comcast.net      +1 303 898 9780

Zhengrong Yao wrote:
> Hi Bob:
> 
> That's a new interesting point for me, but I'm not sure I follow it:
> How could you avoid second O/A exchang when precondition is needed.
> 
> Alice need to signal to you (Bob) the "a=inactive" to "a=sendrecv"
> change isn't it? could this really be fixed by media capabilities
> extention without second O/A?  
> 
> pls treat this only as one question instead of a counterexample.
> 
> BR
> Zhengrong
> 
>  
> 
> -----Original Message-----
> From: Bob Gilman [mailto:bob_gilman at comcast.net] 
> Sent: den 10 april 2008 22:10
> To: Flemming Andreasen
> Cc: Zhengrong Yao; mmusic at ietf.org
> Subject: Re: [MMUSIC] SDPCapNeg : 2nd o/a via UPDATE?
> 
> Flemming-
> Thanks for reminding me of the problem of old middleboxes.
> I was thinking of the 1 of N codec selection problem in section
> 10.2 of RFC 3264.
> -Bob
> -------------------------------------------------------------
> Bob Gilman        bob_gilman at comcast.net      +1 303 898 9780
> 
> 
> 
> Flemming Andreasen wrote:
>> The second O/A exchange is technically speaking never needed; it's 
>> done as a courtesy to any potential middle-boxes that may not 
>> understand the SDP capability negotiations.
>>
>> -- Flemming
>>
>> Bob Gilman wrote:
>>> I think it's always possible, using media capabilities, to frame an 
>>> offer such that there is no need for a second O/A exchange.
>>> I'd be interested in seeing counterexamples.
>>> -Bob
>>> -------------------------------------------------------------
>>> Bob Gilman        bob_gilman at comcast.net      +1 303 898 9780
> 
> 


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