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<p class="MsoNormal">Hello list,</p>
<p class="MsoNormal">I have troubles with serial forking in
kamailio 3.2.4, which is mixed with parallel forking. In the
scenario that an initial INVITE message, which is addressed to
<a href="sip:A" target="_blank">sip:A</a>, is coming in to the
server, it is doing a lookup in the DB and forking (parallel)
the request to e.g. 3 SIP user agents. I have set the timer to
20 seconds transaction timeout and after that timeout, the
server is handling the original request in the
FAILURE_ROUTE[xy]. In this failure route, the request-URI
username is overwritten to an alternative one – e.g.
<a href="sip:B" target="_blank">sip:B</a>. Then the server is
doing a DB lookup again and forking the request to the number of
registered user agents.</p>
<p class="MsoNormal">A specialiy of this scenario is that it can
be possible, that user agents have registered for username “A”
and username “B” – in other words: they are members of the
parallel forking group in serial forking step 1 and step 2. When
the CANCEL and INVITE message would be sent out (to the user
agents) in the correct order, then it would be no problem. But
in my case the server is sending the “new” INVITE message (2<sup>nd</sup>
step in the serial forking procedure) to user agents BEFORE the
CANCEL request. Therefore, these user agents are rejecting the
INVITE message with “500”.<br>
<br>
Signalisation scenario<br>
==================<br>
</p>
<p class="MsoNormal">INVITE -> SRV<br>
SRV -> INVITE (branch-1) UA1<br>
SRV -> INVITE (branch-2) UA2<br>
SRV -> INVITE (branch-3) UA3<br>
SRV <- 180 (branch-1) UA1<br>
SRV <- 180 (branch-2) UA2<br>
SRV <- 180 (branch-3) UA3<br>
..... [timeout]<br>
SRV -> CANCEL (branch-1) UA1<br>
SRV -> CANCEL (branch-2) UA2<br>
SRV -> INVITE (branch-4) UA4<br>
SRV -> INVITE (branch-5) UA5<br>
SRV -> INVITE (branch-6) UA3 (!!!)<br>
SRV -> CANCEL (branch-3) UA3<br>
SRV <- 500 (branch-6) UA3<br>
</p>
<p class="MsoNormal">It was quasi reproduceable that only the last
branch of the initial transaction had that timing problem
(INVITE <- vs -> CANCEL).<br>
My question is: why does the server send the (last) CANCEL
message only after the INVITE message for some branch(es)? Could
this behaviour be prohibited in any way?<br>
</p>
<p class="MsoNormal">Thanks in advance!</p>
<p class="MsoNormal">Klaus</p>
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