[Serusers] ACK message Via field branch=0 problem

[Andrei Pelinescu-Onciul]

On Jul 16, 2004 at 19:09, ks lf <ksabc at lycos.com> wrote:
> Use SER 0.8.12 stable release, enabled nathelper+rtpproxy for NAT traversal, forward 1(xxx)xxx-xxxx to SIp termiantion gateway, when the call was connected, PSTN gateway send 200 OK back, sip client ( behind NAT ) response with ACK ( which has branch value in Via head ), but when SER forward the ACK back to PSTN gateway, in Via header it includes branch=0, PSTN gateway refuse this ACk because it think the branch id is invalid, so call was dropped after 30- 60 seconds, what's wrong with that? I really appreciate if you met such problems before, thanks, and have a nice day.
> 

What kind of gateway do you use? Seems really too picky (an ACK to a 200
Ok is not part of the transaction anyway, and checking for branch
magic numbers and rejecting the message if not present is really 
exagerated). Does it work with ACK without branch in Via (e.g. you can
tests this by connecting directly the Cisco ATA to the gateway, without
going through the proxy).

To workarround this try to add to ser.cfg
syn_branch=0

(this would force full branch computation even for stateless forwards,
like the ACK to 200 Ok case).


Andrei