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CUCM 7.0 upgrade Dilemma

Dear All

I have 2 call mangers 4.x the first one act as a primary at the HQ and the other is subscriber (in Different Location) with fail over WAN Scenario with a 512kb frame relay between them

The total phones registered on both sides is about 250-280 phones I want to upgrade both sides to CUCM 7.x do I have to upgrade the WAN link between

the 2 sites and what is the minimum band width required and how to calculate it ?

thank you in advance


Amer Abu zied

  • IP Telephony

Re: CUCM 7.0 upgrade Dilemma


The SRND for CUCM 7.x has a section covering clustering over than WAN

One of the statements in the document says:

In addition to the bandwidth required for Intra-Cluster Communication Signaling (ICCS) traffic, a minimum of 1.544 Mbps (T1) bandwidth is required for database and other inter-server traffic for every subscriber server remote to the publisher.

I think that you will need a WAN upgrade, particularly if the FR link supports voice traffic plus other data.

Hope this helps

VIP Super Bronze

Re: CUCM 7.0 upgrade Dilemma

Yes, you will need to upgrade the WAN bandwidth by quite a bit. The UCM SRND covers this quite well and it is broken in to two sections:

The first is the general WAN Considerations for clustinering across the WAN. Here is an excerpt from that section; however, it is not a substitution. RTFM in this case.

A minimum of 1.544 Mbps (T1) bandwidth is required for Intra-Cluster Communication Signaling (ICCS) for 10,000 busy hour call attempts (BHCA) between sites that are clustered over the WAN. This is a minimum bandwidth requirement for call control traffic, and it applies to deployments where directory numbers are not shared between sites that are clustered over the WAN. The following equation may be used as a guideline to calculate the bandwidth for more than 10,000 BHCA between non-shared directory numbers at a specific delay:

Total Bandwidth (Mbps) = (Total BHCA/10,000) * (1 + 0.006 * Delay), where Delay = RTT delay in msec

The second important piece is Bandwidth Provisioning section of the Network Infrasturcture chapter. This covers the details on how the bandwidth will be broken down and the math needed to properly design the WAN-facing policy maps. I suggest reading it prior to ordering bandwidth from the provider.

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