T1 Channel selections

[bluejays]

Hi, I have 4 T1 PRI setup, so total I have 92 B Channels. From the test I did, it seems the router select the B channel randomly. Is that the case? Is there any document talking about this?

Thanks.

[Chester Rieman]

On the D channel:

isdn bchan-number-order ?

ascending B-chan selection starting from B1

descending B-chan selection starting from B23/32

[bluejays]

Thanks for your reply. I guess I didn't make myself clear. I have PRI setup for incoming PSTN calls. I want to know how the Ingress Voice Gateway select which B-Channel should answer the PSTN calls.

Thanks.

[Chester Rieman · Accepted solution]

For incoming calls, the switch that is sending the setup message decides on the bchan to use. In the setup message you will see the requested channel and if it is and exclusive channel or a preferred channel.

You can see this with 'debug isdn q931'.

[bluejays]

Thanks alot. I appreciate your input

[bluejays]

By the way, what do the "preferred" and "exclusive" means? Let me give a shot and pls correct me if I am wrong.

Preferred--Switch will decide which channel to use

Exclusive--Ingress gateway will decide which channel to use.

Thanks.

[Chester Rieman · Accepted solution]

Preferred means that the channel shown in the setup message is preferred but that another channel can be used if the GW requests it. Exclusive means that the channel indicated in the setup message must be used.

Hope this helps