[asterisk-users] Outgoing SIP calls dropped after 30 seconds.

[Doug]

At 14:15 11/7/2008, SIP wrote:
 >Kurt Knudsen wrote:
 >> Specs: Asterisk 1.4.22 running behind a SonicWall (transparent mode)
 >> with a public IP address. We have our phone system setup as 172.16.2.x
 >> that connect through the SonicWall to Asterisk. Incoming calls work
 >> flawlessly and we no longer get one-way audio. We are only using SIP
 >> (3 trunks now, instead of 2) and having all 3 in use is not an issue.



 >> Question: Why does it sometimes work and sometimes not? This makes no
 >> sense and it happens on all phones. Any suggestions?
 >>
 >>
 >>
 >
 >
 >We see this on occasion. It sounds a lot like Asterisk doing its usual
 >routine of deciding that you can't POSSIBLY have a call going through
 >because it can't receive an ACK response properly.  Asterisk tries
 >several times to send an ACK and get a response. If the remote system
 >routes ACKs differently than it routes everything else, often times
 >those ACKs get lost, and Asterisk assumes that the call can't be
 >working, so it destroys it.
 >
 >ACK handling is a bit tricky in the real world, and we've run across
 >countless incorrectly-configured SIP servers that don't handle it
 >properly, so calls to them last just about exactly 30 seconds and then
 >drop.
 >
 >There is, unfortunately, no way to turn off Asterisk's 'intelligent'
 >behaviour in this scenario short of possibly patching the code.

http://lists.digium.com/pipermail/asterisk-users/2007-May/187951.html