[SR-Users] tcp hangup

Juha Heinanen jh at tutpro.com
Tue Apr 5 15:10:32 CEST 2011

i turned out that the problem below was caused by a firewall that
blocked tcp session if it had been idle for a few minutes.  the problem
went away when i reduced tcp_connection_lifetime from 3610 to 120 sec.

i don't know if it possible to configure tcp_connection_lifetime on per
connection basis.  for example, tcp connection to UA could have
tcp_connection_lifetime=3610, since tcp session is kept active by UA
sending crlfs, whereas tcp connection to another proxy could have a
shorter tcp_connection_lifetime.

-- juha


> > i did some more debugging and wireshark shows that the 3.0 sr does not
> > even try to send anything to the 3.1 sr over the tcp connection although
> > netstat now tells at both hosts that the connection is established.
> > instead sr 3.0 replies immediately after receiving invite from ua:
> > 
> > SIP/2.0 477 Unfortunately error on sending to next hop occurred (477/TM)
> > 
> > there is no related messages in syslog.  perhaps tcp stack on 3.0 host
> > has not got acks for earlier packets and just waits there.
> The most likely candidates are:
> - blacklisted destination (due to some previous error).
>   You could check it with sercmd dst_blacklist.view or
>    dst_blacklist.debug.
> - some local firewall rules on the OUTPUT chain
>   running out of memory (but it's strange that you don't get any log
>   messages)

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