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CCM bandwidth.

I am using CCM 6.1.

Publisher - Subscriber = 40ms should be the RTD. Are there any value of RTD between the IP Phone and the CCM Server. Also would like to know how about if I put the IP Phones over WAN. How much BW would be required for the phones to connect with the centralized server.

Thanks in Advance


Re: CCM bandwidth.

RTT of 800+ ms are common for sites via VSAT. WAN codec will be g729 rather g711. The most important requirement is that the round-trip delay from one server to any other server needs to be less than 40 milliseconds. It's also good to allocate about 1.5Mbps bandwidth for intra-cluster communication. A good practice is to change your QOS policies so that intra-cluster communication gets better than best-effort service. The easiest way to do that is to use ACL's and match based on source and destination IP address, making sure that any traffic from any CCM server to any other CCM server will be matched. The BW problems may have been due to interrupted intra-cluster communication.

Cisco Employee

Re: CCM bandwidth.

that number has changed with the 6.1 release, it's 40 ms one way or 80 round trip, not 40 round trip as in previous releases.


The maximum one-way delay between any two Unified CM 6.0 servers should not exceed 20 msec, or 40 msec round-trip time (RTT). Beginning with Cisco Unified CM Release 6.1, the maximum one-way delay between two Unified CM servers can be up to 40 msec, or 80 msec round-trip time. Measuring the delay is covered in Delay Testing. Propagation delay between two sites introduces 6 microseconds per kilometer without any other network delays being considered. This equates to a theoretical maximum distance of approximately 3000 km for 20 ms delay or approximately 1860 miles. These distances are provided only as relative guidelines and in reality will be shorter due to other delay incurred within the network.

i recommend you going thru this whole doc

Bandwidth Provisioning



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if this helps, please rate

Re: CCM bandwidth.

Reg BW required for IP phones over the WAN with centralized CCM...

1. Voice Signaling BW - B/W IP Phone & CCM = <2kbps

2. Voice media B/w - B/W 2 IP phones - 26Kbps approx per call

Apart from this, I think you need to consider firmware upgrades to the phones which takes some decent BW (not aware about exact figure).



With best regards... Ashok ----------- Pls kindly rate if helpful or answered your question.
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Re: CCM bandwidth.

To add to these great points, the RTT for clustering accross the WAN were adjuested as pointed out to 80ms, however you need more bandwidth as the delay increments (check out SRND for more details). As far as the phones delay I would suggest staying below 200 ms as you may notice delay issue when you go over that number, i.e. delay dial tone, etc (slightly). 800 ms will surly create noticable delay, i.e. you press speaker button you'll wait 2 or so seonds before it engages, etc.


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