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Maximum Concurrent Calls Over WAN from One Location to Another Location.


Hi Team,


                We have deployed with One Call Manager which is used to 2 locations for registering phones. One Location is Head Office where the Call Manager is Present, Other location where the IP Phones are connected to the Call Manager while MPLS Line and extension calls are happening from one location to another location. 


                  I have doubt how many concurrent calls  will happen over from one extension of location 1 to one extension of location 2  through MPLS Lease Line.


                   Thank you 

4 Replies 4

Nipun Singh Raghav
Cisco Employee
Cisco Employee
It would depend on the Region that you have set for these locations. Inter-Region BW will quote the BW usage per call. This would further tie to the maximum bandwidth that you define for calls between them through location configuration. CUCM does not account for any sort of a L4/L3/L2 overhead. You need to keep in mind that when you define the bandwidth etc.

Also with your WAN you would not want to exceed the CIR defined by your ISP to conform with any sort of DSCP policies and avoid any traffic policing that your ISP might do if you exceed the BW.

Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"

Mohammed al Baqari
VIP Advisor VIP Advisor
VIP Advisor
-##Look at cucm srnd deployment models. It has very nice explanation of how
to size mpls. Basically two main elements:
- what codec is used and how many concurrent calls including layer 3 header
and l2 technology used (ethernet, frame relay, mpls, etc.)
- what signaling protocol used at remote and how many endpoints (each
protocol has amount of bandwidth per endpoint).

In addition there are other elements such ad CTI is used, etc

Dennis Mink

you can use RTMT to monitor location bandwidth, this way you can see how much you would need to allocate

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Chris Deren
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

What is your MPLS provider configured for under the QoS priority queue? You need to align it with your Location bandwidth configuration in CUCM, it requires you convert the values based on the expected codecs and L2 connection.  Assuming your QoS priority queue is set to 512 kbps which over MPLS yields 512K/32.8kbps (g729 call) --> 15 calls (always round down), then 15  * 24 kbps (CUCM calculation for G729 call) = 360 kbps, this is the value you use for the location link between HQ and remote site.

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