Example: Configuring Virtual T1 Channelized ISDN PRI Trunks

This example shows how to configure a virtual channelized ISDN PRI trunk for an SRX210 or SRX240 device with Integrated Convergence Services.

• Requirements
• Overview
• Configuration
• Verification

Requirements

This example uses the following components:

• An SRX210 or SRX240 device with Integrated Convergence Services
• A single-channel T1 Mini-PIM installed in the device

Before you begin, at a minimum configure:

• The SRX Series MGW.
• Stations for the deployment.
• Peer call server information.

Overview

The ISDN standard prescribes a level of service called Primary Rate Interface (PRI) implemented for a T1 line, that providing telecommunications services to offices. A T1 line can provide 24 channels. However, for the SRX210 and SRX240 devices with Integrated Convergence Services, the T1 Mini-PIM only provides a single channel. To emulate a T1 line with multiple channels, Integrated Convergence Services implements ISDN PRI.

An ISDN PRI T1 line can provide 24 channels composed of 23 B-channels (or bearer channels) and 1 D-channel (or adata channel). Time slot 24, which is used as the D-channel, carries control and signaling information. Each of the 23 B-channels (time slots 1 to 23) is used as a discrete voice trunk, and each B-channel is essentially equivalent to other trunks on the device, including T1E, analog, and SIP trunks. Although an inband T1 line has 24 channels, the 23-channel ISDN PRI can set up more calls faster because of the dedicated signaling D-channel. For ISDN PRI T1 lines, the network carries the contents of the B-channel transparently between endpoints of the call.

This example assumes that the SRX210 device with Integrated Convergence Services is used as a customer-premises equipment (CPE) device located at the customer site or branch office. The T1 line connects the customer site to a central office (CO) or to a service provider that acts as the CO.

For the ISDN PRI implementation, an incoming call that specifies a DID number is routed over the PRI T1 line to the destination station if DID is configured for that station. If DID is not configured for the station, the call is directed to auto attendant.

This example configures the following parts:

• The ISDN PRI options for the channelized T1 (CT1) interface.
  • B-channel time slots, allocated in ascending order
  • National ISDN-2 (NI-2) as the ISDN switch type
  • Voice as the media type

    Note: You cannot configure the virtual CT1 interface on an SRX210 or SRX240 device with Integrated Convergence Services to support data transmission. By default, the configuration assumes data. Therefore, you must explicitly configure voice as the media type.

• The partitions and time slots for the PRI channels.
  • Partition 24 is dedicated to the D-channel and used timeslot 24.
  • Partitions 1, 2, 3, and 4 are configured for the B-channels using timeslots 1, 2, 3, and 4 respectively.
• The ISDN PRI T1 trunk.
  • The CT1 interface specifies four partitions and four B-channel time slots. Similarly, the trunk configuration specifies four partitions and four B-channel time slots for the PRI group.

    Note: The maximum number of time slots assigned to ISDN PRI depends on the TDM capacity of the device. The number of time slots configured for the PRI group must be within the TDM capacity of the device. The SRX210 device with Integrated Convergence Services supports up to 16 channels. The SRX240 device with Integrated Convergence Services supports up to 42 channels.

    Note: CT1 time slots that are not allocated for the PRI group remain unused and cannot be allocated to another group. To ensure maximum utilization of an ISDN PRI trunk, specify the number of time slots for the PRI group that are defined in the partition time slots for the interface without exceeding the TDM capacity of the device.

• The physical network connector interface on the chassis. Configure the FPC parameters for FPC 1 as follows:
  • The PIC as PIC 0.
  • The port number as port 0.
  • The transmission rate as Digital Signal Level 1 (DS-1).

    DS-1 is the logical bit pattern used over a physical T1 line for access to the telecommunications network.

  • The mode as CT1 for voice over PRI.

Configuration

• Configuring ISDN PRI for a CT1 Interface
• Configuring PRI Channels on a CT1 Interface
• Configure a T1 Trunk for PRI
• Configuring a T1 Mini-PIM

Configuring ISDN PRI for a CT1 Interface

CLI Quick Configuration

To quickly configure ISDN PRI for the CT1 interface, copy the following commands and paste them into the CLI.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see “Using the CLI Editor in Configuration Mode.”

To configure ISDN PRI for the CT1 interface:

1. Specify the CT1 interface name.
   [edit interfaces]user@host# edit ct1-1/0/0 isdn-options
2. Specify the order for allocating B-channel time slots.
   [edit interfaces ct1-1/0/0 isdn-options]user@host# set bchannel-allocation ascending
3. Specify the ISDN switch type.
   [edit interfaces ct1-1/0/0 isdn-options]user@host# set switch-type ni2
4. Configure the media type for the interface.
   [edit interfaces ct1-1/0/0 isdn-options]user@host# set media-type voice
5. Specify the clocking method.
   [edit interfaces ct1-1/0/0]user@host# set clocking external

Results

From configuration mode, confirm your configuration by entering the show interfaces ct1-1/0/0 isdn-options command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Configuring PRI Channels on a CT1 Interface

CLI Quick Configuration

To quickly configure PRI channels on the CT1 interface, copy the following commands and paste them into the CLI.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see “Using the CLI Editor in Configuration Mode.”

To configure PRI channels on the CT1 interface:

1. Configure the D-channel partition and time slot.
   [edit interfaces ct1-1/0/0]user@host# set partition 24 timeslots 24 interface-type dc
2. Configure the B-channel partition and time slots.
   [edit interfaces ct1-1/0/0]user@host# set partition 1 timeslots 1 interface-type bc user@host# set partition 2 timeslots 2 interface-type bc user@host# set partition 3 timeslots 3 interface-type bc user@host# set partition 4 timeslots 4 interface-type bc

Results

From configuration mode, confirm your configuration by entering the show interfaces ct1-1/0/0 command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

For brevity, this show command output includes only the configuration that is relevant to this example. Any other configuration on the system has been replaced with ellipses (...).

If you are done configuring the device, enter commit from configuration mode.

Configure a T1 Trunk for PRI

CLI Quick Configuration

To quickly configure the T1 trunk for PRI, copy the following commands and paste them into the CLI.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see “Using the CLI Editor in Configuration Mode.”

To configure the T1 trunk for PRI:

1. Configure the T1 trunk name and its interface.
   [edit services convergence-services]user@host# set trunk t1 trunk-type t1 tdm-interface ct1-1/0/0
2. Configure the PRI group for the T1 trunk.
   [edit services convergence-services]user@host# set trunk t1 trunk-type t1 pri-group time-slots 1-4

Results

From configuration mode, confirm your configuration by entering the show services convergence-services trunk t1 command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Configuring a T1 Mini-PIM

CLI Quick Configuration

To quickly configure the T1 trunk for PRI, copy the following commands and paste them into the CLI.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see “Using the CLI Editor in Configuration Mode.”

To configure the T1 Mini-PIM:

1. Configure the Mini-PIM for the chassis.
   user@host set set chassis fpc 1 pic 0 ds1 pic-mode voice-ct1

Results

From configuration mode, confirm your configuration by entering the show chassis fpc 1 command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verification

To confirm that the configuration is working properly, perform this task:

• Verifying That the SRX Series MGW Is Active

Verifying That the SRX Series MGW Is Active

Purpose

Verify that the SRX Series MGW is active. Display the length of time that the Integrated Convergence Services media gateway call routing engine has been executing.

Action

From operational mode, enter the show services convergence-services media-gateway uptime command.

Related Topics

• Understanding ISDN PRI Support for Voice Traffic
• SRX Series Integrated Convergence Services Media Gateway Overview
• Understanding the SRX Series Integrated Convergence Services Media Gateway