Clustered Call Manager Distance Limits

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Sep 30th, 2010
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We are looking at bringing in an Office in San Francisco into our Call Manager Cluster. We are located in Connecticut. Has anyone ever done this? What are the hard distance limits for a cluster?



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Overall Rating: 3 (2 ratings)
Lakshmi Adapala Thu, 09/30/2010 - 09:51
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Please refer to the SRND Deployment Models, clustering over the WAN, under:

* Delay

The maximum one-way delay between any Cisco CallManager servers for all priority ICCS traffic should not exceed 20 ms, or 40 ms round-trip time
(RTT). Delay for other ICCS traffic should be kept reasonable to provide timely database and directory access. Measuring the delay is covered in.

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.

pener1963 Thu, 09/30/2010 - 10:41
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So New York to San Fran is just plain out of the question?

If so,how do big companies with offices on each coast do this?

Thanks again,


Lakshmi Adapala Thu, 09/30/2010 - 12:43
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Hi Pete,

This distance limitations applies to the nodes that are part of the same callmanager cluster (ICCS singaling), that is if you have a node in SJ office that needs to talk to the pub over the WAN. In case of large customers they might be having different callmanager clusters that communicate via the Inter cluster trunks between them.



cristobal.priego Thu, 09/30/2010 - 13:41
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if you have 2 clusters,

one cluster in San Francisco and one cluster in New York 2 independent clusters,

I'd use ICT (Inter Cluster Trunk) Gatekeeper controlled

just my two cents


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