Understanding ISDN Interfaces

ISDN provides two basic types of service, Basic Rate Interface (BRI) and Primary Rate Interface (PRI).

This topic contains the following sections:

• ISDN BRI Interface Types
• ISDN PRI Interface Types
• ISDN Interface Configuration

ISDN BRI Interface Types

BRI is an ISDN service intended for home and small enterprise applications. ISDN BRI consists of two 64-Kbps B-channels to carry voice or data and one 16-Kbps D-channel for control and signaling.

ISDN BRI is designed for high-bandwidth data transmissions through existing telephone lines. The copper wires that make up much of the existing telephony infrastructure can support approximately 160 Kbps, which provides enough bandwidth for two B-channels and a D-channel, leaving 16 Kbps for any data framing, maintenance, and link control overhead.

Up to six of the following field-replaceable units (FRUs) are available for ISDN BRI connectivity:

• 4-port S/T PIM supporting ITU-T I.430, ETSI TS 101080, and GR-1089-Core Type III
• 4-port U PIM supporting ANSI T.601 and GR-1089-Core

A J Series device with one or more ISDN BRI ports has the following types of ISDN interfaces:

• Physical ISDN BRI interface—br-pim/0/port
• Physical B-channel interface—bc-pim/0/port
• Physical D-channel interface—dc-pim/0/port
• Logical dialer interface—dln

Each ISDN BRI port has two B-channels for transport, identified as bc-pim/0/port:1 and bc-pim/0/port:2, and one D-channel for control, identified as dc-pim/0/port. On ISDN BRI interfaces, the B-channels and D-channel have no configurable settings, but you can monitor them for interface status and statistics.

To configure ISDN BRI service on a J Series device, you configure the physical ISDN BRI interface and the logical dialer interface.

ISDN PRI Interface Types

ISDN PRI is designed for users with greater capacity requirements than can be met with ISDN BRI. In the United States, the most common PRI supports 23 B-channels to carry traffic and 1 D-channel for control and signaling, totalling 1,536 Kbps, which is roughly equivalent to a T1 link. In Europe, the most common PRI supports 30 B-channels and 1 D-channel, totalling 1,984 Kbps, which is roughly equivalent to an E1 link.

For ISDN PRI, up to six Dual-Port Channelized T1/E1/ISDN PRI PIMs, supporting ITU-T Q.920, Q.921: LAPD, Q.930, and Q.931, are available for ISDN connectivity.

On a J Series device with one or more Dual-Port Channelized T1/E1/ISDN PRI PIMs, you can configure each port on the PIM for either T1, E1, or ISDN PRI service, or for a combination of ISDN PRI and either T1 or E1 service. For ISDN PRI service, you configure the following types of ISDN interfaces as channels on the channelized T1 or E1 interface:

• Physical B-channel interface—bc-pim/0/port:channel
  • On a channelized T1 interface, up to 23 time slots can be configured as ISDN PRI B-channels.
  • On a channelized E1 interface, up to 30 time slots can be configured as ISDN PRI B-channels.
• Physical D-channel interface—dc-pim/0/port:channel
  • On a channelized T1 interface, you configure time slot 24 as the D-channel.
  • On a channelized E1 interface, you configure time slot 16 as the D-channel.
• Logical dialer interface—dln

ISDN Interface Configuration

To enable ISDN interfaces to work properly, you must configure the interface properties:

• Calling number—This number represents the caller's number. It is sent to the ISDN switch during the call setup.
• Service provider ID (SPID)
• Static terminal endpoint identifier (TEI)—This number comes from your service provider. Valid values range from 0 to 63. If you are using a service provider that requires SPIDs, you cannot place calls until the interface sends a valid, assigned SPID to the service provider when accessing the ISDN connection.

  When configuring the static TEI value, please note the following: If the field is left blank, the device dynamically acquires a TEI. If you have configured a second SPID, you cannot set a static TEI value. If you have a NTDMS-100 or NI1 switch, an additional box for a service provider ID is provided.

• Incoming called number—Configure incoming call properties if you have remote locations dialing into the device through the ISDN interface.

In addition to configuring ISDN properties, you must set the following additional ISDN values:

• Dialer pool—Dialer pool priority has a range from 1 to 255, with 1 designating lowest-priority interfaces and 255 designating the highest-priority interfaces.

• ISDN switch type—The following switches are compatible with J Series devices:

  • ATT5E—AT&T 5ESS
  • ETSI—NET3 for the UK and Europe
  • NI1—National ISDN-1
  • NTDMS–100—Northern Telecom DMS-100
  • NTT—NTT Group switch for Japan
• Q.931 timer interval—Q.931 is a Layer 3 protocol for the setup and termination of connections. The default value for the timer is 10 seconds, but can be configured between 1 and 65,536 seconds.
• TEI negotiation value—You must specify when the TEI negotiates with the ISDN provider. If you specify first-call, activation does not occur until a call is sent. If you specify power-up, activation occurs when the device is powered on. This is the default value.

Related Topics

• Junos OS Feature Support Reference for SRX Series and J Series Devices