Extension Mobility across clusters?

[Randall White]

Is it possible to have extension mobility between Call Manager clusters?

We currently have each office as a stand alone cluster w/ it's own Publisher. I would like to have extension mobility for users that travel between offices.

Is this possible? Or would I need to have centralized call processing (1 Publisher)?

Thx, Randy

[vmoopeung]

Thanks for the detailed explanation. As far as I know Extension Mobility between clusters is not supported by call manger. The reason is that the device profile which is an integral part of configuring the extension mobility does not get exchanged between two different clusters. You need to have centralized call processing (1 Publisher)

[dearjwe]

Randy,

You might want to consider a centralized cluster with a Publisher at one site and a Subscriber at the other. If successful, you can provide extension mobility to both sites and it will provide you with the survivability that the centralized cluster is lacking.

I am still doing research on this but I have found out that Cisco will provide TAC support if your delay is less than 40ms. If its more than that (as almost all are) then you are on your own. I am planning to test this soon. Remember that if you want to attempt this, you should make sure to create your cluster locally, then disperse the servers over the WAN so that the entire database does not have to replicate over your link.

Let me know how it goes...

J

[ckatene]

I have a plan for doing this. I'd be interested in knowing what you think. We have seen a request for such a service, and are just waiting for the customer to give the go ahead for the development work.

It involves a standalone application server acting as a TFTP switch. Users can access a phone app from the services button of their phone, which returns a list of registered clusters. user selects a cluster, the app server notes the selection, then uses AXL to reset the phone. the app server is the primary TFTP server, and when the phone reboots the TFTP requests from the phone are forwarded to the publisher selected by the user. hey presto! once the phone has come up it is registered with the target cluster and the user can simply login using extension mobility.

do you think this would work?

[padutelindus]

Seems a good idee to solve this issue with a service this way, but it will be very difficult to manage. It meens you need to configure all IP Phones worldwide on every callmanager cluster within your network and that you will consume a lot of WAN bandwith when calling.

Creating a single cluster between al locations is very dificult! There you need to have a Round Robin delay of less than 40ms BETWEEN ALL CALLMANAGERS and a minimum bandwith of 900k only for syncronisation.

For the momment we solve it by installing IP Communicators on mobile users PC and configuring the TFTP-address staticly.

[dearjwe]

I'm not sure about the replication, but I would think you could use the the CallManager Group and Device Pool configurations to have phones register with the nearest CallManager. Then use Call Admission Control and Regions to limit the absorbtion of your bandwidth resources.

Is there somewhere that specifically states that the replication across a WAN is 900k? If worse came to worse, I would think about making the replication occur once at the lowest point in the day (2am)?

Please, more thoughts and or suggestions.