First Invite in this figure is really a re-Invite. Pl. refer to the text
accompanying this figure:
Let's assume, that in the middle of the session, A wishes to change
the IP address where it is receiving media. Figure 3 shows this
scenario.
SDP1: A includes an offer in a re-INVITE (1)
>-----Original Message-----
>From: Sarkar, Uttam [mailto:[EMAIL PROTECTED]
>Sent: Tuesday, October 31, 2006 3:56 PM
>To: Sanjay Sinha (sanjsinh); [EMAIL PROTECTED];
>[email protected]
>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>
>Here is that figure. I don't see any re-INVITE at all.
>Here INVITE (1) had 200 OK (7) and ACK (8).
>No further re-INVITE.
>
>
>
> A B
>
> | |
> |-------------(1) INVITE SDP1--------------->|
> | |
> |<------(2) 183 Session Progress SDP2--------|
> | *** *** |
> |--*R*-----------(3) PRACK-------------*R*-->|
> | *E* *E* |
> |<-*S*-------(4) 200 OK (PRACK)--------*S*---|
> | *E* *E* |
> | *R* *R* |
> | *V* *V* |
> | *A* *A* |
> | *T* *T* |
> | *I* *I* |
> | *O* *O* |
> | *N* *N* |
> | *** *** |
> | *** |
> | *** |
> |-------------(5) UPDATE SDP3--------------->|
> | |
> |<--------(6) 200 OK (UPDATE) SDP4-----------|
> | |
> |<-----------(7) 200 OK (INVITE)-------------|
> | |
> |------------------(8) ACK------------------>|
> | |
> | |
>
>
>-----Original Message-----
>From: Sanjay Sinha (sanjsinh) [mailto:[EMAIL PROTECTED]
>Sent: Tuesday, October 31, 2006 3:48 PM
>To: Sarkar, Uttam; [EMAIL PROTECTED];
>[email protected]
>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>
>
>
>>-----Original Message-----
>>From: Sarkar, Uttam [mailto:[EMAIL PROTECTED]
>>Sent: Tuesday, October 31, 2006 3:17 PM
>>To: Sanjay Sinha (sanjsinh); [EMAIL PROTECTED];
>>[email protected]
>>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>>
>>I see UPDATE is used before sending 200 OK (for INVITE). I don't see
>>any re-INVITE scenario here. Am I missing something here?
>
>Yes. Pl. see sec. 13.1, Figure 3.
>
>
>>
>>-----Original Message-----
>>From: Sanjay Sinha (sanjsinh) [mailto:[EMAIL PROTECTED]
>>Sent: Tuesday, October 31, 2006 2:56 PM
>>To: Sarkar, Uttam; [EMAIL PROTECTED];
>>[email protected]
>>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>>
>>I think RFC 3312 has some examples where 18x is needed for
>>preconditions in a mid-call session.
>>
>>Sanjay.
>>
>>>-----Original Message-----
>>>From: Sarkar, Uttam [mailto:[EMAIL PROTECTED]
>>>Sent: Tuesday, October 31, 2006 2:05 PM
>>>To: Sanjay Sinha (sanjsinh); [EMAIL PROTECTED];
>>>[email protected]
>>>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>>>
>>>Whole idea of 100rel is to make sure 18X message is received by the
>>>other party so that they can be sure of exchnage any media before
>>>session is established.
>>>Re-INVITE is for established session.
>>>Please correct me if I am wrong.
>>>
>>>-----Original Message-----
>>>From: Sanjay Sinha (sanjsinh) [mailto:[EMAIL PROTECTED]
>>>Sent: Tuesday, October 31, 2006 1:09 PM
>>>To: Sarkar, Uttam; [EMAIL PROTECTED];
>>>[email protected]
>>>Subject: RE: [Sip-implementors] Query 100rel in re-INVITE
>>>
>>>It might be useful for QoS cases.
>>>
>>>>-----Original Message-----
>>>>From: [EMAIL PROTECTED]
>>>>[mailto:[EMAIL PROTECTED] On Behalf
>>>Of Sarkar,
>>>>Uttam
>>>>Sent: Tuesday, October 31, 2006 11:28 AM
>>>>To: [EMAIL PROTECTED]; [email protected]
>>>>Subject: Re: [Sip-implementors] Query 100rel in re-INVITE
>>>>
>>>>I still can't understand why 100rel is requiring to a
>>>re-INVITE (change
>>>>media from audio to audio and video).
>>>>In the re-INVITE it will carry the new media. Other endpoint will
>>>>respond back with final response (like 200 OK or 488 Not Acceptable
>>>>Here).
>>>>I can't imagine other end will send 18X with media and send
>>>PRACK for a
>>>>session that is already established.
>>>>
>>>>Thanks,
>>>>
>>>>-----Original Message-----
>>>>From: [EMAIL PROTECTED]
>>>>[mailto:[EMAIL PROTECTED] On Behalf Of
>>>>[EMAIL PROTECTED]
>>>>Sent: Tuesday, October 31, 2006 10:57 AM
>>>>To: [email protected]
>>>>Subject: Re: [Sip-implementors] Query 100rel in re-INVITE
>>>>
>>>> From: "Sarkar, Uttam" <[EMAIL PROTECTED]>
>>>>
>>>> 100rel does not make sense in re-INVITE as session is already
>>>> established. UAS is expected to send final response
>>>(2XX/4XX/5XX etc
>>>>).
>>>> It can send 100 trying to stop retransmission of INVITE
>while it's
>>>> preparing the final response.
>>>> It's not recommended for UAS to send 1XX response for the
>>>re-INVITE.
>>>>
>>>>One can imagine scenarios where a re-INVITE might not be
>>>instantaneous,
>>>>and so 100rel might be a useful mechanism. For instance, if one
>>>>endpoint wishes to upgrade an audio call to an
>audio-and-video call,
>>>>the other endpoint might want to ask its user before activating the
>>>>video camera.
>>>>
>>>>Dale
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>>>>
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>>>>
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>>>
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