ISDN PRI and T-1

[kobchai7037]

Hello,

Could anybody please explain to me what the different between PRI and T-1?

What is the difference between the companys that have T-1 and ISDN PRI?

Thank you

[travis-dennis_2]

In the most braod and general terms a T1 is used for data (Internet access, etc.) and a PRI is a T1 where the line has been broken down into channels ans used for voice (phone lines).

A full T1 will give you 1.54Mbps of connection speed to the Internet. You can also get fractional (cheaper) T1s that do not offer the full amount of bandwidth.

You can have up to 24 channels on a PRI, 23 for voice and 1 for data so you could potentially have up to 23 phones calls on your gateway at anyone given time.

Depending on your provider though you may also be able to use a T1 for voice and data (Cbeyond for example). Most PRI lines have a single channel available for data as well but it is gennerlly only 64 or 128 Kbps.

I hope this answers your question in a decent fashion. Please reply if there is anything else you need.

Please remember to rate all replies.

Thanks,

Travis

[smif101]

The T1 transmits DS-1 formatted data at 1.544Mbs at the most basic level. The T1 then has several flavors to it like CAS (call associated signaling) and PRI. PRI is how it is stated above and CAS takes bits within the DS0's for call control. Then you can have just a unchannelized T1 for data circuits.

[davp9353]

What happens when you have half a PRI? does it mean you then have 12B channels and 1D channel? if so, how would you define the 12 channels and a D as the 13th on a Cisco 2651XM router?

Everytime I try to define 13 channels (12B+1D) timeslots 1-13 I get channel D to default at 24 instead of 13. What am I doing wrong?

[smif101]

Have you tried creating the interface as such

Router# configure terminal

Router (config)# isdn switch-type primary-5ess

Router (config)# controller T1 3/1/1

Router (config-controller)# framing esf

Router (config-controller)# linecode b8zs

Router (config-controller)# pri-group timeslots 1-13

Router (config-controller)# exit

Router (config)# interface serial 3/1/1:12

Router (config-if)# ip address 1.1.15.1 255.255.255.0

After you create the pri-group and it automatically creates the D channel on slot 24 then you might need to delete that interface and recreate it as i have above.

[davp9353]

When I tried to do just that I got the following:

router(config)#no in Serial1/0:23

% Removal of channelized E1/T1 interface configuration is not permitted.

Remove timeslot configuration on controller to remove Serial1/0:23 interface.

router(config)#int Serial1/0:12

% Cannot access B-channel interfaces

When I create the pri-group timeslots 1-13 it automatically creates the D channel on 23

Is there any other way to override the d channel on 23?