CUCM 5.1(3) location-based cac "strange" behaviour

Unanswered Question
Feb 12th, 2009

Hello all,

Here is the configuration:

- 1 main site in "hub_none" location

- 1 remote site in "B14" location

- "B14" configured with 96Kbps.

- 15 phones and 2 mgcp endpoints in location "B14"


1) incoming call from pstn on the remote gw

2) remote site operator phone answer the call

3) RTMT do not show any bandwidth consumned in "B14" location

4) operator initiate a transfert to remote site extension (same device pool, same location)

5) G.729 MOH is played from central site

6) RTMT show 72Kbps available in the location

7) operator try to terminate the transfert but it's impossible because location "B14" get OutOfRessource (cf. RTMT)

Can anyone help me understanding why CUCM refuse to complete the transfert ?

Thanks a lot.


I have this problem too.
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Aaron Harrison Fri, 02/13/2009 - 09:16


1,2,3 all seem fine, as the call originates and terminates in the same location 'B14'. Locations tracks only the bandwidth used between a location and any other location (e.g. hub_none).

4,5 - here, as G729 is streamed from hub_none to B14, 24Kbps is assigned as used. CCM doesn't know the exact bandwidth used by a call (which varies depending on the L2 transmission media and other things) so it assumes G729=24Kbps, and G711=80Kbps.

6 - 96 - 24 = 72, which is correct.

7 - I presume the Operator is attempting to transfer to Hub_none or another non-B14 location? It would appear that whatever the Operator is trying to transfer to must be configured for G711 only and be in a location other than B14. As CCM requires 80Kbps for this call, it is rejected.

If you increase the locations bandwidth from 96 to 104, it will allow the transfer.

When you set up locations, you generally don't configure the exact REAL bandwidth you have available - you work out how many G729 or G711 calls you can fit into your real bandwidth, taking into account overhead and so on. You then calculate the figure that will enforce the correct limit on CCM.

E.g. you know you can pass 3 G729 calls accross the WAN, so you assign 72K to the location, even though in reality the calls may take 90K.

It's best to not mix G711 and G729 on the same link, as it makes the maths difficult.



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jtoque Mon, 02/16/2009 - 01:10

Thank you Aaron, i agree with you but the call has to be transfered in G.711 to an ip phone in "B14" location (same location, so CUCM does not have to apply any restriction).

I don't understand why during the transfer operation, the CUCM behave like there is a call setup from "hub_none" to "B14" location in G.711 codec (instead of G.729) !

Is this because of the call that is previously connected to the MOH server ???

Thanks again for your help.



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