Using an Atlas 550 as a "PSTN Switch"

[Anonymous]

I am considering outfitting a single Atlas 550 with four quad-T1 cards and then using it to interconnect Cisco routers, with the idea that the routers and the CUCM they support will use the T1 as a "pstn" gateway. This is for Voice over IP training, where I may have as many as 12 student routers up and running at one time

Each of the routers would actually only get a few DS0 in the T1 - as few as four, depending on the number of active routers in the class. This would be manually configured/managed.

Their DS0 would be cross-connected to one of two T1s that are connected to another router that is playing PSTN switch (I have not yet decided if a router will be sufficient here or if I need to go to Asterisk on a PC).

So my questions --

First, what pitfalls can I expect doing this kind of cross-connect? Things to consider for something this large, such as timing?

Second, can the Atlas 550 itself do the "pstn" switching? Can it recover dialed digits and switch the DS0 to the appropriate T1/DS0 group, or is the external "pstn" switch a must?

I appreciate any advice or suggestions

[Anonymous · Accepted solution]

The ATLAS can act as a "PSTN Switch" for use in a lab environment. You can look at this document for some older Cisco Academy configuration guides. This two sections in this guide covers BRI switching and then PRI switching, so you will have to make adjustments if you are doing RBS signaling on the T1 instead of PRI.

You definitely need to take timing into consideration. The ATLAS only supports one timing source, so if the ATLAS timing is set to INTERNAL then everything else will take timing from the ATLAS.

If the ATLAS is acting as the PSTN then it will route the calls based on the IN#ACCEPT lists and there must be a match for the ATLAS to route it.

If you are doing RBS signaling then you may have to adjust the NUMBER COMPLETE TEMPLATE under the DIAL PLAN and GLOBAL PARAMETER. The default templates start with a 7-digit pattern, and then goes to a 1+10-digit pattern for long distance. If you are doing 10-digit dialing or something other than 7-digit dialing (such as 4-digit) then you will either have to adjust this template, or modify the END OF NUMBER TIMEOUT (which defaults to 16 seconds).

Hope this helps,

Patrick

[Anonymous]

Patrick,

Thank You for replying so quickly

So if i understand you correctly, with some dial plan work, I should not need to offload to another device for the actual call switching...the T1s will simply terminate at the ADTRAN?

Jim

[Anonymous]

Yes, the ATLAS can do the call switching when configured under the DIAL PLAN. It will use the IN#ACCEPT lists to decide how to route the calls. The USER TERM and NETWORK TERM are in reference to what the ATLAS is terminating to, so under USER TERM the ATLAS is terminating to user equipment and is in a network role.

Patrick

[Anonymous]

Great, Thank You!

One last question- i would like to prototype this; can I use the T1 cards I have in the NETWORK slots to do this, or do I need to stick with getting the appropriate cards to put into the USER slots.

Thanks Again

Jim

[Anonymous]

You can use the Network modules to do this. Any of the T1 modules/ports can be configured as either NETWORK TERM or USER TERM. You will need a T1 cross-over cable to connect the ATLAS to the end equipment though, because the ports on the ATLAS are T1 and not DSX-1.

Patrick