>>i)             why a proxy cannot generate reliable provisional responses to
>>requests sent within the context of a dialog. ...and

I think this is because once the dialog is up, the call is now end-to-end.
So, reliable provisional responses would be sent end-to-end.


>>ii)             why UAS MUST NOT attempt to send a 100 (Trying) response
>>reliably ..

The 100 Trying does not need to be acknowledged because it doesn't
contain any important information (it is only an acknowledgement).
If the 100 is not successful, then the INVITE will be re-transmitted,
and this will cause the 100 Trying to be re-transmitted.

In other words, the retransmission of the INVITE 
encourages reliability of 100 Trying anyway.


Regards,
Attila



-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of
Nithyakumar.R
Sent: 01 February 2007 07:44
To: [email protected]
Subject: [Sip-implementors] PRACK doubt....


 

 

Hi ,

 

I have doubt in PRACK message..

 

i)  Proxy  MUST NOT attempt to sent reliable provisional responses.for any
request that contains tag in the To field. That is, a proxy cannot generate
reliable provisional responses to requests sent within the context of a
dialog. 

 As per RFC 3262.. (section 3 .. UAS Behavior)

 

 

ii) A UAS MUST NOT attempt to send a 100 (Trying) response reliably.

 

Can Anyone help me to understand these statement...

 

i)             why a proxy cannot generate reliable provisional responses to
requests sent within the context of a dialog. ...and

ii)             why UAS MUST NOT attempt to send a 100 (Trying) response
reliably ..

 

 

 

Thanks in advance..

 

Regards,

Nithyakumar.R

Huawei Technologies India Ltd.,

 

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