ISDN Overview

Integrated Services Digital Network (ISDN) is a set of standards for digital transmission over different media created by the Consultative Committee for International Telegraph and Telephone (CCITT) and International Telecommunication Union (ITU). As a dial-on-demand service, it has fast call setup and low latency as well as the ability to carry high-quality voice, data, and video transmissions. ISDN is also a circuit-switched service that can be used on both multipoint and point-to-point connections.

You configure two types of interfaces for ISDN service: a physical interface and a logical interface called the dialer interface.

ISDN provides a Services Router with a backup connection for network interfaces.

ISDN Interfaces

There are four types of interfaces available for ISDN connectivity:

• 1-port S/T interface supporting ITU-T I.430, ETSI TS 101080, and GR-1089-Core Type III built into a J2300 Services Router with additional network interfaces.
• 1-port U interface supporting ANSI T.601 and GR-1089-Core built into a J2300 Services Router with additional network interfaces.
• 4-port S/T PIM supporting ITU-T I.430, ETSI TS 101080, and GR-1089-Core Type III as a field-replaceable unit (FRU) on all J-series Services Routers except the J2300.
• 4-port U PIM supporting ANSI T.601 and GR-1089-Core as a FRU on all J-series Services Routers except the J2300.

Each ISDN physical interface uses the naming convention br-pim/0/port.

Each B-channel is identified by bc-pim/0/port:channel, where channel represents the B-channel ID and has a value of 1 or 2.

The D-channel is identified by dc-pim/0/port.

For information about interface names, see Network Interface Naming.

The B- and D-channel interfaces do not have any configurable parameters. However, when interface statistics are displayed, the B- and D-channel interfaces list statistical values.

The dialer interface, dln, is a logical interface for configuring dialing properties for ISDN connections. The interface can be configured in two modes:

• Multilink mode using Multilink PPP encapsulation
• Normal mode using PPP or Cisco High-Level Data Link Control (HDLC) encapsulation

The dialer interface cannot be configured simultaneously in the following modes:

• As a backup interface and a dialer filter
• As a backup interface and dialer watch interface
• As a dialer watch interface and a dialer filter
• As a backup interface for more than one primary interface