asterisk users - Jan 2008 - Sip calls drop one leg after about 2 minutes

Hello all,
I know this has been discussed before but I am not finding the thread on 
voip-info or site:lists.digium.com through google.

I have a site with * ver. 1.4.15 (started out as 1.4.2 or so) running on 
openSuSE 10.2, Dual core AMD Opteron, purely SIP.
I haver been experiencing a problem where after about 2 min 10 seconds 
to 2 minutes 18 seconds incoming audio stops.  The call is still up but 
no inbound audio. At first I thought the calls was dropping completely 
but that is not the case. iirc there was a similar problem a while back 
in * versions.  I looked on voip-info but did not find anything that 
appeared to be the same issue.  This does not happen on all calls, maybe 
4 or 5% of calls.

I am not finding anything in the log files to tell me what is going on.
I am going to upgrade to 1.4.17 tonight and see if there is any 
difference.  Any suggestions of what to look at or where to go (keep it 
clean ;-) please) would be greatly appreciated.
Thanks in advance
JohnM
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At 14:54 1/10/2008, John Millican wrote:
 >Hello all,
 >I know this has been discussed before but I am not finding the thread on
 >voip-info or site:lists.digium.com through google.
 >
 >I have a site with * ver. 1.4.15 (started out as 1.4.2 or so) running on
 >openSuSE 10.2, Dual core AMD Opteron, purely SIP.
 >I haver been experiencing a problem where after about 2 min 10 seconds
 >to 2 minutes 18 seconds incoming audio stops.  The call is still up but
 >no inbound audio. At first I thought the calls was dropping completely
 >but that is not the case. iirc there was a similar problem a while back
 >in * versions.  I looked on voip-info but did not find anything that
 >appeared to be the same issue.  This does not happen on all calls, maybe
 >4 or 5% of calls.
 >
 >I am not finding anything in the log files to tell me what is going on.
 >I am going to upgrade to 1.4.17 tonight and see if there is any
 >difference.  Any suggestions of what to look at or where to go (keep it
 >clean ;-) please) would be greatly appreciated.
 >Thanks in advance
 >JohnM

NAT?

http://www.google.com/search?q=Asterisk+dropped+calls+NAT