[SIPForum-discussion] SIP reliable response ..

[Bharat Sarvan]

There is no extra information in the content except for the Supported Header
containing 100rel extension in the response.

The reliability mechanism works by mirroring the current reliability
mechanisms for 2xx final responses to INVITE.  Those requests are
transmitted periodically by
the Transaction User (TU) until a separate transaction, ACK, is
received that indicates reception of the 2xx by the UAC.  The
reliability for the 2xx responses to
INVITE and ACK messages are end-to-end.  In order to achieve
reliability for provisional responses, we do nearly the same thing.
Reliable provisional responses
are retransmitted by the TU with an exponential backoff. Those
retransmissions cease when a PRACK message is received. The PRACK
request plays the same
role as ACK, but for provisional responses.

-Bharat



On Mon, Apr 26, 2010 at 12:39 PM, Murali Vuppandla <mvuppand at cisco.com>wrote:

>  When there is a Required/Supported header contains 100rel tag  in INVITE
> then UAS will send a reliable response, after which it has to be
> acknowledged with PRACK. But when it comes to the actual content of the
> message, what makes Reliable responses different from normal SIP provisional
> responses.
>
>
>
> Means to say what other extra information does it carry ???  Please clarify
> me.
>
>
>
> Regards,
>
> Murali.
>
>
>
>
>
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