[cisco-voip] Callmanager cluster in Wan

[Wes Sisk]

I've seen many deployments that use this model.  Noteworthy items:
1.register a phone and gw in the US to the EU servers and test the 
timing.  With high RTT cm<->gw and cm<->phone users may notice a delay 
in audio cut through when answering calls.  Faststart for h323 and 
optimized mgcp help some, but delays can still become an issue.  I will 
post a followup message with details when I locate them.
2. dialpan on EU servers will become significantly more complex hosting 
PSTN patterns for US and EU
3. Consider SRST for the US site, possibly using multiple SRST routers 
to allow all phones to register in the event of any network outgate 
between US and EU.
4. if you deploy 3rd gen ipphones (7941/7961/7911/7970/7971, etc.) be 
aware of upgrade issues due to TFTP over high RTT.  Strongly consider 
upgrading to CM version and phone versions that support peer to peer 
firmware sharing. (cm6.0 srnd page 3-15)

More details of this are covered in the SRND:
http://www.cisco.com/go/srnd
Your scenario is covered under "multi-site wan with centralized call 
processing' but depends on information in other sectsions as well.


/Wes

Leonardo D'Urso wrote:
> Hi there
>
> A customer of mine have two site: one in EU, one in USA with two different clusters of callmanager. Actually there is a trunk that permits to call between. 
> I have users that want to have the same extension mobility profile on each side. 
> I have evaluated that with a latency of 120ms it is not possible to have 1 centralized ccm cluster infrastructure with 1pub and 2sub in EU and 1 sub in USA. But what happens if i have all ccm server in a single location EU and a single voice gateway with SRST in USA and the  ip phones that directly point to ccm cluster in EU?
>
> Regards
> Leo 
> ---
> Leonardo D'Urso
> l.durso at gmail.com
>
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