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I have a customer with 2 data centres two 2900 ISR and a sip trunks for PSTN available at each site

my understanding is I create a h.323 connection from CM to each GW then a SIP connection using CUBE to the sip provider

for inbound the sip provider will load balance accorss the two trunks

for out bound load balancing  can just add both gateways into a route group?

will I need cube licences on both GWs because I want to use them in an active /active mode?

CUBE talks about media preservation is this inbuilt?

when would I need a sip proxy

Anything else I need to be aware of from a high level design point of view


Cisco Employee

Re: CUBE DEsign

Assuming you are running CM 6 or higher, run SIP-to-SIP CUBE.  With H323-to-SIP CUBE you need to require an MTP for all outbound calls to get early-offer.  With SIP-to-SIP CUBE you can use early-offer forced on CUBE to achieve it.  I'm going to base the rest of my answers upon the fact that you are going to go with a SIP-to-SIP CUBE.

Yes, place both CUBE trunks in the same route group with 'circular' as the logic for load balancing.  If you want load balancing for inbound calls coming into CUBE from the ITSP, your provider will have to configure that on their end, which you mentioned they are setup for.

Yes you will need to purchase CUBE licenses for both devices.

No need for a SIP proxy here, that I can see.

Run 15.1(2)T1.  Make sure you have 'mid-call signaling passthru' and 'early-offer forced' configured.

Regarding media preservation:

Cisco UBE does not support call preservation. If an Cisco UBE is located
 between a gateway and a Cisco Unified Communications Manager that have 
call preservation configured and the Cisco UBE is configured with media 
flow-around, calls will be preserved on the gateway when the Cisco UBE's
 IP interface becomes inaccessible due to a network issue or a reload. 
In this case, call preservation behavior on the gateway will be the same
 as the case where there is no Cisco UBE between the gateway and the 
Cisco Unified Communications Manager. Calls that are "held" will not be 
preserved as the Cisco UBE passes the nonstandard "do not preserve" 
indication sent in the Notify message from Cisco Unified Communications 
Manager to the gateway.

If you have session refresh disabled on the provider side and on CM for these calls, and if you are doing media flow-through (default/recommended), the audio should stay up if CM goes down, as long as no MTPs are invoked.  It will then use the media inactivity timer to know when to tear the audio stream down.

We can do media preservation if CUBE goes down, with this feature:

Note, though, that since signaling isn't preserved, you still can't use session refresh on CM or the ITSP if you want media preservation to last longer than half of the session refresh timer.

Hope this helps some.

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