ISDN connections are delivered in two variants, PRI - Primary Rate Interface and BRI - Basic Rate Interface.

PRI is the standard for connections to offices. It's based on a T1 line in the US,
and E1 line in Europe. The T1 PRI consists of 24 channels, the E1 PRI of 32.

PRI has varying number of channels depending on the country.
In North American and Japan it's 23xB + 1xD (23 64Kbps digital channels + 1 64Kbps signalling/control channel) on a T1 1.544 Mbps
In Europe and Australia it's 30xB + 2xD on an E1 2.048 Mbps
(One timeslot on the E1 is not available for the user since it is used for internal synchronization purposes.)

PRI is also available in partial variants - ie 10xB + D.

  • Question: What about outside US and Europe - what's being used?
  • Answer: Most of the rest of the world use E1. Japan uses a variant of T1.

NFAS (Non Facility Associated Signalling) allows sharing one D channel accross multiple PRI.

As well as 'standard' signalling there are vendor specific extentions to PRI. The relevant standards include:
  • National ISDN v1 aka. NI-1
  • National ISDN v2 aka. NI-2 (see SR-4994)
  • Nortel DMS100, DMS250 (see NIS-A211-1)
  • Lucent 4ESS, 5ESS (see TR 41459)
    • some recent versions of the 5ESS support protocol extensions that Lucent refers to as Natianal ISDN v3 aka. NI-3


If you are experiencing the "0x84" problem, here is why:

If you have run into the error of: "Do not handle argument of type 0x84"

Notify your Carrier immediately that they are not correctly or that they are not currently posting CALL NAME to your PRI.

Please see: Digium Lists-Ast-2004-Oct-003790 and look for "0x84" being referred to as: #define ROSE_NAME_NOT_AVAIL

This will show that your carrier is not providing inbound Caller Name to your PRI.

This will interfere with caller name display and asterisk.


ISDN in the United States is a "RETAIL" tariffed service. When you go back up the food chain to the ILEC and IXC level, carriers do not inteconnect with a PRI. They use DS0 (analog trunk), DS1 (T1), DS3 (28 T1's), OC-n, and Ethernet (VOIP).

They will "sell" you a PRI, but this product is not in any of their interconnection agreements that take place between "carriers".

James Taylor

With many ILECs and CLECs, the same circuit is often available under multiple names and tarrifs. Many carriers charge a base rate for the DS1 circuit and additional charges per B channel or PSTN interconnect). When you order a PRI circuit, very carefully examine the different tarrifs that are available to ensure that you are getting the best circuit for your needs. It is not uncommon for a partial PRI to cost significantly more than a full PRI because of the tarrif that the provider has chosen to market agressively.

See also

Created by: oej, Last modification: Mon 06 of Dec, 2010 (15:23 UTC) by rkelley
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