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
No comments:
Post a Comment