Hi Sergey,

Second INVITE is because of retransmission. Probably that why there is 1 at the end for second INVITE. That makes sense, cause when call is answered Kamailio cancel transaction with ID z9hG4bK5398.d5b303bd66f82a3f5cf66672ff787b76.1.

Branch parameter is identifying transaction. Bye is separate transaction and that why it has different branch parameter. ACK is separate transaction too, that why it has different branch parameter too.

Check image below for detailed info about transaction and dialog.

http://www.kamailio.org/pub/ser/ser-releases/0.8.12/doc/html/figures/transaction.png

With kind regards,

Jurijs

On Fri, Sep 23, 2016 at 2:09 PM, Sergey Safarov <s.safarov@gmail.com> wrote:

Hello gys
Could you please help me resolve issue with Kamailio.
In attached file call from freeswitch to endpoint via Kamailio proxy.
In packets 3 and 4 kamailio sends two INVITES with different branches in "VIA" header for IP 10.21.19.10 ("SIP/2.0/UDP 217.12.247.212;branch=z9hG4bK5398.d5b303bd66f82a3f5cf66672ff787b76.0" and "SIP/2.0/UDP 217.12.247.212;branch=z9hG4bK5398.d5b303bd66f82a3f5cf66672ff787b76.1").

Then from endpoint Kamailio gets 100, 180 and 200 messages (packets 5, 6, 8, 9) with appropriate branches in "VIA" header.

Then Kamailio in packet 11 send CANCEL for branch "z9hG4bK5398.d5b303bd66f82a3f5cf66672ff787b76.1"
And in packet 13 send "ACK" with new branch "SIP/2.0/UDP 217.12.247.212;branch=z9hG4bK5398.8ba6e3c3c63533fae1ceff3074f476fb.0"
In packet 14 endpoint confirms CANCEL of call with branch "z9hG4bK5398.d5b303bd66f82a3f5cf66672ff787b76.1".

And then in packet 16 strange message from Kamailio with branch "SIP/2.0/UDP 217.12.247.212;branch=z9hG4bK6398.f0bbae920c6f81401d10d39f23335696.0".

Could you suggest correct answer for following questions:
are is kamailio incorrectly changes branch values in VIA header;
what is RFC numbers where is described proxy behavior for branch value in "VIA" header.

Sergey Safarov

Interest page https://andrewjprokop.wordpress.com/2014/03/06/understanding-the-sip-via-header/

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