Re: PRACK: Does non-200 response cease re-transmission ofreliable 18x?

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Hi, 

>>>Is the flows below valid according to recent arguments? 
>>> 
>>>   UAC                  UAS 
>>>    |----invite(SDP)--->| 
>>>    |<--- 183(SDP)------| 
>>>    |-----prack(SDP)--->| 
>>>    |<--- 200(SDP)------|
>>>
>>>       flow 1
>>>  
>>Assuming the 200 is the PRACK response, yes.
>>>  
>>>   UAC                  UAS 
>>>    |----invite-------->| 
>>>    |<--- 183-----------| 
>>>    |-----prack(SDP)--->| 
>>>    |<--- 200(SDP)------|
>>>   
>>>       flow 2
>>>  
>>Not valid. If the INVITE does not contain SDP, a reliable answer must 
>>contain SDP. We are currently discussing whether the FIRST reliable 
>>response must contain SDP, or whether that rule can be related. But, 
>>that is a separate thread.
>
>Hmm. That flow is a consequence of changing that rule that I had not
previously considered.
>
>Allowing flow 2 would cause all sorts of trouble. If the restriction on
offer in first reliable provisional is to be 
>relaxed it must be sure to state that the first offer must then be in
*some* reliable provisional, and until that is sent 
>there can be no offer sent another way (PRACK or UPDATE).
>
>Just opening that question is enough to make me more concerned about
relaxing the constraint.

I am not proposing to allow flow 2, and I don't think relaxing the rule
would allow it either. The rule would say that if the INVITE does not
contain an SDP offer the SDP offer must be carried in a reliable
response. The PRACK can only contain an SDP offer if the UAC has receied
an SDP answer.

Regards,

Christer

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