asterisk users - Oct 2007 - maximum retries exceeded on transmission Warnings

Hello All,
I've got the following warning messages a couple of days back:
/chan_sip.c: Maximum retries exceeded on transmission <SIPcallId> for 
seqno 1 (Critical Response).

/Have got the warnings repeatedly for one Callid. If maximum retries 
have exceeded why should it give me those warnings again n again for the 
same callid, with a gap 4 seconds between each warning.
The callids mentioned in the warnings are of the inbound leg.

I've scoured the net, but haven't got anything conclusive. Have found 
responses ranging from firewall issues, no reception of ACKs, to bugs in 
some versions of Asterisk.

I am using Asterisk 1.4.4, all SIP calls, with PSTN termination provided 
by my service provider. Have no firewalls or iptables set on my server.
The calls did not seem to work even across a restart of asterisk.
Interestingly, the calls to and from the very same numbers worked later 
on the next day.

Anyone faced similar problems and was able to get the root of it? Or is 
it a bug?

cheerz
- Ben







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