asterisk users - Jun 2010 - SIP message problems - retransmit and lost messages

I have an asterisk system in Costa Rica that connects to a SIP provider in
Atlanta. Sometimes SIP packets seem get dropped or retransmitted too quickly.

In trying to debug this I turned on SIP debug in Asterisk and the SIP provider
enabled packet capture on his end.

What I saw was me sending an invite, them sending a 100 Trying, me sending a
cancel, me sending a retransmit of the cancel, me sending another retransmit of
the cancel, them sending a 200 ok, them sending a 488 Not Acceptable Here, and
then me sending an ACK.

What they saw was the invite from me, them sending the trying, me sending two
cancels, them sending an ok, me sending a cancel and them sending an ok.

I have two questions.

First is can I change the time Asterisk waits before doing the retransmit?

Second is they do not take down the call because I guess the sequence of packets
is not acceptable to them so we end up with hundreds of calls that Asterisk
thinks have been dealt with but the provider still thinks are pending some
action. Can something be done from the Asterisk side to deal with this
situation?
-- 
Jim Dickenson
mailto:dickenson at cfmc.com

CfMC
http://www.cfmc.com/