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Community Member

CallManager IP Phone Distance Limitation!

Is there any set distance that an IP phone that will be homed back to a centralized cluster must no exceed? I know in a distributed call processing cluster the server can be no more than 40ms round trip, 3000km/1890 miles away.

Does the time have to do with the amount that you set in the callmanager service parameter for the phone and the callmanager to see other and be able to respond back to one another by its keepalives?

Thanks in advance


Re: CallManager IP Phone Distance Limitation!

40ms RTT is not for a distributed call processing cluster, but for callmanagers (pub and subs) with in the same cluster. I have seen a few issues with POE when the distance of the cable run (300ft) is close to 300 ft...other than that there shouldnt be any problems.


Community Member

Re: CallManager IP Phone Distance Limitation!

I am always bad with naming conventions but what I was referecning was the clsutering over the WAN. So you can have a cluster here in the US and have an IP phone hang off of it in lets pick a far away point Ukraine and not have any delay to dial tone or have it constantly loose connectivity?

Thanks for the response.


Re: CallManager IP Phone Distance Limitation!

You can a phone registered with remote cluster as far away as you want if networking infrustructure is in place. Even with delay over 1 sec the conversation will be very acceptable AS LONG AS jitter is minimal and QoS is in place. I have IP phone (in US) registered with cluster in Mexico and sometimes conversation is ok. We don't have QoS and network is heavily oversubscribed. But if there is good infrustructure there should be no problem.

Don't even try VPN tunnel between countries. Chances are it will not work.

Community Member

Re: CallManager IP Phone Distance Limitation!

Thanks for everyone's replies and time that you spent out of your busy days.


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