[SR-Users] Does Kamailio support PRACK ?

[Alex Balashov]

PRACK is an in-dialog/sequential request, which will be relayed like 
other.  So, Kamailio relays it in the same way that it supports any 
sequential request.  Is it not necessary for a SIP proxy to do anything 
specific to support PRACK.

The UAC should not be increasing the CSeq when sending a PRACK.  My 
guess is that it is the UAS which doesn't like it, rather than 
Kamailiio.  From RFC 3262 Section 3 ("UAS Behavior"):

    A matching PRACK is defined as one within the same
    dialog as the response, and whose method, CSeq-num, and
    response-num in the RAck header field match, respectively,
    the method from the CSeq, the sequence number from the CSeq,
    and the sequence number from the RSeq of the reliable
    provisional response.

-- Alex

On 05/13/2013 11:37 AM, Alex Solt wrote:

> Hi,
>
> Does kamailio support PRACK method ? Any configuration change is needed?
> It appears Kamailio does not like the PRAK when increasing Cseq.
> Here is the call flow:
>
> A send INVITE --> Kamailio --> proxy the packet to B
> B send 180 Ringing --> Kamailio -> proxy the packet to A
> A send PRAK  (increase Cseq) --> Kamailio --> proxy the packet to B
> B send 200 OK --> Kamailio -> proxy the packet to A
> Kamailio re-send 180 Ringing to A
>
>
> Thanks,
> AS
>
>
>
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-- 
Alex Balashov - Principal
Evariste Systems LLC
235 E Ponce de Leon Ave
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Web: http://www.evaristesys.com/, http://www.alexbalashov.com/