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

[Flemming Andreasen <fandreas at cisco.com>]

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
>
>
>
> Flemming Andreasen wrote:
>> The normal SIP and offer/answer rules apply here and hence use of 
>> UPDATE for the second O/A exchange is indeed an option. Note however, 
>> that the initial O/A exchange must always complete first, and hence 
>> you either need to receive a 200 OK, or use reliable provisional 
>> responses.
>>
>> -- Flemming
>>
>> Zhengrong Yao wrote:
>>> Hi:
>>>  
>>> Maybe an obsolete question but I did not manage to find hint in the 
>>> MMUSIC email threads...
>>>  
>>> Although nothing preventing this but is it good to suggest in 
>>> application to send 2nd round o/a exchange within UPDATE message, 
>>> meaning that Alice and Bob can start session already after 1st round 
>>> o/a exchange, and dont need to wait until the 2nd round (unless it 
>>> has to be done in another INVITE SIP message). Of course issues in 
>>> 3.12 remains the same.
>>>  
>>> In draft now the text for 2nd round read as:  "Alice’s updated 
>>> offer..." Is this an indication for usiing UPDATE to do 2nd o/a 
>>> exchage or?  it makes "2nd delay" less scary.
>>>  
>>>  
>>> Thanks a lot for tips
>>>  
>>> BR
>>>  
>>> Zhengrong Yao
>>>
>>>
>>>
>>> *Zhengrong Yao*  Ph.D.
>>> Standardization Manager
>>> *Ericsson AB*
>>> Business Unit Multimedia                          Office: +46 46 194584
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>>> _Zhengrong.Yao at ericsson.com_ <mailto:Zhengrong.Yao at ericsson.com>
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