[asterisk-users] Calls hang up after 20 seconds

[SIP]

Gianni Fioretta wrote:
> Hello.
>
> I have a problem with Asterisk, sometimes it hangs up an external call after 20 seconds, apparently without any reason.
> The call comes from a SIP server hosted from EuteliaVoIP, many peers rangs and one of them answer, the call ends itself after 20 seconds from the answer.
> I've tried many configuration in sip.conf, but no one solved the problem.
>
> Log from /var/log/asterisk/messages:
> [Oct  8 15:49:05] WARNING[10659] chan_sip.c: Hanging up call E3F0204B-B35811DE-BBA58889-6D53C3C3 at 83.211.2.220 - no reply to our critical packet.
>
> and from CLI:
> [Oct  8 15:52:26] WARNING[10659]: chan_sip.c:1950 retrans_pkt: Maximum retries exceeded on transmission 59E62874-B35911DE-9A598915-C5A6B3AA at 195.62.226.16 for seqno 101 (Critical Response)
> [Oct  8 15:52:26] WARNING[10659]: chan_sip.c:1972 retrans_pkt: Hanging up call 59E62874-B35911DE-9A598915-C5A6B3AA at 195.62.226.16 - no reply to our critical packet.
>   == Spawn extension (incoming, 03411885583, 4) exited non-zero on 'SIP/03411885583-081e0d78'
>
> (peer 101 was not connected at this time, but Asterisk also hags up with all the peers connected)
>
> Any idea?
>
> Thanks in advance.
>
>   
This is a very weird Asteriskism that we see from time to time. Some SIP
servers don't route ACK packets properly (or there will be an ACK loop).
The nature of ACK packets is.... tenuous at best in the SIP world. Many
clients don't even send them. Asterisk relies heavily on ACK packets to
determine if a call is currently connected. If it doesn't receive one,
it hangs up the call, even if the rest of the packets have been routed
properly and the call is working fine.

There's no configuration to turn this off, but there is a way to remove
the check in the code. I can't recall the appropriate line to comment
out, though. Perhaps someone else knows?

In an ideal world, when Asterisk sent an ACK, whatever server/client it
was connected to would respond accordingly. It is, however, not an ideal
world, so this doesn't always happen.

N.