MGCP and partial timeslots

[Phil Bradley]

Hello. I am trying to configure timeslots on my 2911 router with the pri-group timeslots 1-20,24 service mgcp command. However when I do this I cannot receive a call through the PRI. What happens is the outside caller gets a fast busy but I can see the calller id info on the internal phone. The D channel appears to be functioning but maybe MGCP with call manager is overwriting the setting above. Is there a setting in call manager that will set the timeslots above? The original problem was that I did not have enough DSP resources available for all 23 channels so I had use the pri-group timeslots 1-20,24 command to allocate my PRI. What I have done so far is remove a FXO card so that I have enough DSP's available and immediately when I powered the router back up MGCP must have sent down the pri-group timeslots 1-24 service mgcp since that is what I see in the router config now. The PRI is now functioning as expected. Do fxo and fxs cards immediately allocate a DSP channel even if not in use and did I miss a setting in callmanager where I could allocate only 20 of the PRI channels? I assume since I have 1-4 port FXO and 2-4 port FXS cards the system automatically allocated 12 DSP channels to those cards which only left me with 20 channels since I have two 16 channel DSP modules installed.

Thanks,

Phil

[Jaime Valencia]

Such configuration is NOT supported, partial PRIs are only supported with H323.

There is a way to do this, once again, not supported. You'll disable channels in CUCM, a quick search on MGCP + partial PRI on CSC will provide you all the details.

HTH

java

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[Rob Huffman · Accepted solution]

Hi Phil,

Your other assumption is correct here, in that when a card/module

like the 4 port FXO is configured the DSP channels are automatically

assigned/allocated for it's use

Cheers!

Rob

[Phil Bradley]

Thanks for the info java and Rob! I just keep finding reasons not to use MGCP between call manager and the gateways. I will search for the document on partial PRI and MGCP but I have two gateways/PRI's and need to see how that will work. Rob, does it also do this for the dsp's on t1 cards? I would have thought that you could dynamically allocate dsp resources as needed.

Thanks!

[Aaron Harrison · Accepted solution]

Hi Phil

PRIs - you assign DSPs when you enter the pri-group timeslots command.

Analogs grab/reserve DSPs at boot, and you can't do anything to stop them!

I have some customers in the UK that have partial E1s, and they simply set 'bottom up' for the selection order. SP sends stuff in on channel 1, and they are effectively starting at 1 as well. Simpler than the solution referred to above, and doesn't seem to cause them problems...

In your case I guess the SP is sending calls in on channel 24 first? You might be able to mirror what my cu has done and set timeslots 5-24 active - allowing the inbound on channel 24, and making sure you are routing to channel 24 as a preference.

But the real solution is to get the correct PVDMs of course...!

Aaron Harrison

Principal Engineer at Logicalis UK

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[Phil Bradley]

Hello Aaron

Thanks for the suggestion above. I tested this and it does work by setting the timeslots to 5-24. By the way thanks for the real solution! Im glad they have a trade-in program for DSP's .

Phil