P Vinod wrote:
> Hi,
>
> In RFC 3262, the following snippet is found:
>
> <Quote>
> The PRACK request plays the same role as ACK, but for provisional responses.
> There is an important difference, however. PRACK is a normal SIP message,
> like BYE. As such, its own reliability is ensured hop-by-hop through each
> stateful proxy. Also like BYE, but unlike ACK, PRACK has its own response.
> If this were not the case, the PRACK message could not traverse proxy
> servers compliant to RFC 2543 [4].
> </Quote>
>
> Could any of the members explain about the last statement:
> If this were not the case, the PRACK message could not traverse proxy
> servers compliant to RFC 2543 [4].
>
> thanks
> PV
PV,
In both 2543 and 3261 the only message that doesn't get a response is
ACK. In both, an unknown message is treated as a normal message and the
beginning of a non-invite transaction. A proxy that doesn't understand
PRACK treats it as a standard non-invite transaction, and this works
because it gets a response.
Paul
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