Call drops at rural CM branch site

[bchris999]

Hi Community,

I have a Comms Manager 8.5 deployment with some remote branch offices. One of these offices is in a rual location and WAN connectivity is not great. CM works fine most of the time, however I am experiencing some mid-call drop outs. The site has a 2911 router with a BRI (ISDN2e) breakout. Calls to the PSTN are sent over the BRI line. (There is no SRST setup yet, but this is planned).

My question is.... if someone at the site makes a (PSTN) call, is on the phone and the WAN drops mid-call (no loss of ISDN), will the user be cut off, or will the call continue despite the phone having lost contact with CM. (If it makes a difference, the handsets are SIP 9971)

Many thanks,

Chris

[Gajanan Pande · Accepted solution]

Already established PSTN call will not be dropped unless there is any issue with BRI connectivity. The only issue will be phone features like, MoH, Conferencing etc will not be available as the phone lost connectivity to CUCM at main branch. Once the PSTN call is finished, phone will reboot as it is unregistered.

If above info helps, pls rate the post.

GP.

[bchris999]

Thanks for the information and the very quick reply. This is what I thought the answer would be unfortunatly.

From the information I have given, can you think of any reason why calls may be dropping out?

Thanks,

Chris

[Gajanan Pande]

If there are mid-call drops between main & remote branch, ensure you have a low-latency link between these 2 sites. Also, ensure that your CUCM location configuration implements the CAC properly. If the location based CAC is not enough, consider deploying Gatekeeper based CAC or best way is to increase the bandwidth between these sites.

Also, see if there are any codec mismatch issues between phones at remote site & MoH servers, Voicemail etc. In your case, the calls are getting established well ( as you explained ) between phones at 2 sites but mid-call if the remote phone tries to access features like MoH etc, the codec mismatch can drop the calls. Pls ensure, you have the transcoder to take care of it.

Above mentioned things should take care of most of the issues.

Hope it helps ?

GP.

[bchris999]

Thanks for the information, however the calls are not between remote and main site, the calls are from the remote site to a PSTN number and breakout to a BRI line at the remote site. The only traffic to the main site is the call control.

Thanks,

Chris

[Gajanan Pande]

ok. In that case, debug outputs on the gateway router will hold the key. Latency plays major role in this case also.

I hope there are no issues from the gateway hardware side ? e.g. CPU high usage, low memory, old IOS with potential bugs. Pls keep them updated & on at recommended version for your CUCM version.

GP.