Configuring Isdn; Overview; Isdn Interfaces - HP MSR Router Series Wan Access Configuration Manual

Configuring ISDN

Overview

Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system that provides
high-quality end-to-end digital connectivity at high rates over copper wire.
ISDN transmits all information in the digital form. It enables a single pair of telephone wires to transmit
data and voice simultaneously at high rates. This feature enables ISDN to provide more services and
higher transmission efficiency than PSTN, where information is transmitted in the analog form.
ISDN provides a set of standard multipurpose user-network interfaces (UNIs). Different services and
terminals can use the same UNI interface to access an ISDN network.

ISDN interfaces

ISDN uses TDM technology to divide a physical interface into one data (D) signaling channel and
multiple bearer (B) channels.
The D-channel transmits control signaling.
•
• The B-channels transmit data or voice.
The ITU-T I.412 recommendation specifies the basic rate interface (BRI) and the primary rate interface
(PRI).
BRI interface
The BRI interface provides two 64 kbps bearer (B) channels and one 16 kbps D-channel. This interface
is also referred to as "2B + D."
The B-channels use timeslots 1 and 2 in the BRI interface.
PRI interface
The PRI interface has two variants: CE1 PRI (ITU-T recommended) and CT1 PRI (ANSI recommended).
CE1 PRI provides 30 B-channels and CT1 PRI provides 23 B-channels. Different countries use different PRI
variants, as shown in
Table 3 PRI interface specifications
Item
Total bandwidth
Timeslots
Timeslot assignment
Table 3.
CE1 PRI (30B + D)
About 2 Mbps
32
•
D-channel—Timeslot 16.
•
B-channels—Timeslot ranges 1 to 15 and
17 to 31.
NOTE:
CEI PRI uses timeslot 0 for clock
synchronization.
109
CT1 PRI (23B + D)
About 1.5 Mbps
24
•
D-channel—Timeslot 24.
•
B-channels—Timeslots 1 to
23.