ISDN timers for MGCP over satellite

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Hello Cisco Netpro,

I'm working on a CM7 installation, with an MGCP voice gateway. The CM is separated from the VGW by a private satellite connection that puts at least a 500ms delay on communications. If there is an error in transmission we could see this delay go over 1000ms.

We're having some problems with incoming calls. Sometimes incoming calls fail, giving silence to the caller. The VGW reports this error from a q931 debug:

Cause i = 0x80E6 - Recovery on timer expiry

The Internet claims that this error is most often seen on outbound calls, but it led me to investigate the t310 ISDN timer. I found that the CM had a t310 set to 60s, and the VGW was set to 30s. So far the only timer I have adjusted is t310, where I have set the VGW to 60s to match the CM.

Nonetheless, these problems persist. The issue is intermittent, which leads me to think that it is related to the huge delay caused by the satellite link.

Can you advise on a proper set of timers to accommodate this network condition? I see there are two Layer 2 ISDN timers that are below 4 seconds that may be appropriate: t200 and t202.

Thanks,

Paul

I have this problem too.
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Paolo Bevilacqua Wed, 11/11/2009 - 14:43

That may not be the answer you're looking for, but if you was to run H.323 or SIP, signaling would be terminated locally, and you would have no issues, plus other advantages.

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