[SIPForum-discussion] [Sip-implementors] [Sipping] how to response the offer

[Dushyant Dhalia]

see my response inline.

Tanu Kapoor wrote:
> Hello SunYongGuang,
>
> A should consider incoming SDP as new offer and answer appropriately, quite
> likely as you mention the offer has not changed it would send a 180 or 200
> OK response with same parameters as negotiated first time.
>
> In any case A should not ignore  the incoming re-invite as that would cause
> B to terminate the session, Section 14.1 UAC behaviour of RFC.
>
> Hope it helps.
>
> Regards,
> -Tanu.
>
> On Wed, Aug 19, 2009 at 12:58 PM, 孙永光 <sammanengineer at gmail.com> wrote:
>
>   
>>  Dear All
>>
>>    I have a question about How to respond the offer , the scenario is as
>> following
>>
>> A call B , and the offer and answer is ok , after a while , A receives a B
>> 's REINVITE which includes the same SDP as it just answered before
>> now, How does A respond it ?
>>
>> does A  must respond  the B's new offer  with   the same SDP as the offer
>> it sent previously?
>>
>> could you give some advice ?
>>     
See Section 8 of RFC 3264 (snippet attached)
At any point during the session, either participant MAY issue a new 
offer to modify characteristics of the session. It is fundamental to the 
operation of the offer/answer model that the exact same offer/answer 
procedure defined above is used for modifying parameters of an existing 
session.
The offer MAY be identical to the last SDP provided to the other party 
(which may have been provided in an offer or an answer), or it MAY be 
different. We refer to the last SDP provided as the "previous
SDP". If the offer is the same, the answer MAY be the same as the 
previous SDP from the answerer, or it MAY be different.

When issuing an offer that modifies the session, the "o=" line of the 
new SDP MUST be identical to that in the previous SDP, except that the 
version in the origin field MUST increment by one from the previous SDP. 
If the version in the origin line does not increment, the SDP MUST be 
identical to the SDP with
that version number. The answerer MUST be prepared to receive an offer 
that contains SDP with a version that has not changed; this is 
effectively a no-op. However, the answerer MUST generate a valid
answer (which MAY be the same as the previous SDP from the answerer, or 
MAY be different.

Dushyant
>> Thanks
>>
>> SunYongGuang
>>
>>
>>
>>
>>
>> --
>> msn:yongguangsun at hotmail.com <msn%3Ayongguangsun at hotmail.com>
>>
>>
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>>
>>     
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