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Specifying particular B-channels for use on ISDN PRI

Hi guys,

We want particular functionality but not sure how to achieve it, either with a backhauled Cisco gateway (2800 series) or a standalone 2800-series gateway.

We have a Cisco 2800 interfacing with a server with an Intel Dialogic card, everything working perfectly. To simplify the scenario, the gateway is currently standalone (using dialpeers for inbound/outbound voice). It is connected to the PSTN via SIP ITSP. Inbound/outbound calls to/from the PSTN to/from the Dialogic card are working fine; there is no problem with that functionality.

We have a 100-block of numbers from the PSTN. We want to segment the 100 numbers such that we can specify a group of channels to use for a particular dialpeer. For example, on a full 30-channel ISDN E1 (I'm Australian, so we use E1 and not T1) I may want 02 9999 8800-8809 to only use channels 20-25 on the ISDN trunk between the 2800 gateway and the Dialogic card.

The only method I'm aware of is specifying ascending/descending order by using "isdn bchan-number-order ascending/descending" from the serial interface of the ISDN PRI, but this is not sufficient and I want more control over B-channels.

I'm able to operate as network side and provide clock for the ISDN PRI connecting to the Dialogic card if required to find a solution.

I'm hoping it's a simple solution and I've simply over-looked something! :-)

Thanks in advance.

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Gold

Re: Specifying particular B-channels for use on ISDN PRI

There is no way in the IOS gateway to direct specific DNIS out specific channels on a PRI.

Incorrect, it is actually possible:

controller x1 y/y/y

pri-group 0 timeslots 1-30

trunk-group tg1 timeslots 1-5

Then reference trunkgroup instead of port in pots DP. Of course, you can create as many TGs as you need.

This said, I would like to see a reference where dialoging uses specific channel numbers in a PRI configuration, as that is never the case in my understanding.

The way to limit calls in range is using a COR configration matching incoming DP with answer-address.

Note: CAS on E1 does not exist in reality, altough configurable on the router.

7 REPLIES
Hall of Fame Super Gold

Re: Specifying particular B-channels for use on ISDN PRI

Why you want to specify B channels, that is never necessary in ISDN.

What you want instread, is to limit the number of calls coming from a certain range(s) of numbers, correct ?

New Member

Re: Specifying particular B-channels for use on ISDN PRI

We run a custom application on the server running the Dialogic card, and specifying the range of channels to use for a particular indial range satisfies the criteria for the software developers.

Alternatively, I'm curious to hear how to limit the number of calls down a particular ISDN from the Cisco side. I've never attempted or researched it but it may be an alternative method the software devs can make use of instead.

Thanks for your prompt response!

Any help appreciated.

New Member

Re: Specifying particular B-channels for use on ISDN PRI

I've not seen anything like this myself from the Cisco side. However if all you are trying to do is limit the number of calls to DDIs then you can use max connections on the dial-peer instead of physically limiting the calls by reserving channels.

Cisco Employee

Re: Specifying particular B-channels for use on ISDN PRI

There is no way in the IOS gateway to direct specific DNIS out specific channels on a PRI.

If you configure it as a CAS circuit (which I know the Dialogic card has the capability of doing), you can break the circuit out into different ds0-groups and do it:

controller t1 1/0

ds0-group 0 time 1-3 type e&m-wink

ds0-group 1 time 4-6 type e&m-wink

ds0-group 2 time 7-9 type e&m-wink

dial-peer voice 1 pots

destination-pattern 1111

port 1/0:0

dial-peer voice 2 pots

destination-pattern 2112

port 1/0:1

Though if you move to CAS, you're going to lose ANI on inbound faxes.

-Steve

Hall of Fame Super Gold

Re: Specifying particular B-channels for use on ISDN PRI

There is no way in the IOS gateway to direct specific DNIS out specific channels on a PRI.

Incorrect, it is actually possible:

controller x1 y/y/y

pri-group 0 timeslots 1-30

trunk-group tg1 timeslots 1-5

Then reference trunkgroup instead of port in pots DP. Of course, you can create as many TGs as you need.

This said, I would like to see a reference where dialoging uses specific channel numbers in a PRI configuration, as that is never the case in my understanding.

The way to limit calls in range is using a COR configration matching incoming DP with answer-address.

Note: CAS on E1 does not exist in reality, altough configurable on the router.

New Member

Re: Specifying particular B-channels for use on ISDN PRI

Steve:

Thanks a lot for that info, it's certainly good food for thought. I'll try giving it a go and update with results (may take a couple of days). Point noted regarding inbound fax.

p.bevilacqua:

Thanks a lot also. I'll try this as well and see how it goes.

The Dialogic card doesn't require specific channels to be used, it's more a design decision of the application that uses/controls the Dialogic card. Point noted regarding COR.

Thanks again.

New Member

Re: Specifying particular B-channels for use on ISDN PRI

Hi guys,

Just to update you all - associating timeslots to trunkgroups under the controller configuration works perfectly. It's exactly what we required.

Thanks a lot for the quick replies.

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