# Digital Links

## Purpose

The Digital Links form assigns descriptor numbers to circuits that serve as digital links. The descriptor numbers are assigned, on a per-link basis, to digital trunk cards. The form also provides space for comments to be made on a per-link basis.

Use this form when performing the following tasks:

- Program BRI Trunks

- Program DASS II Trunks

- Program Embedded BRI

- Program Embedded PRI/QSIG

- Program MSDN/DPNSS Trunks

- Program PRI/QSIG Trunks

- Program T1/D4 Trunks

## Field Descriptions

Parameter | Description | Default Value
Controller Module | System-generated, protected field. Identifies the module position (1-4) in the controller. |
Port | System-generated, protected field. Identifies the port (1 or 2) in the module. |
Unit | System-generated, protected field. Identifies the physical location. |
Shelf | System-generated, protected field. Identifies the physical location. |
Slot | System-generated, protected field. Identifies the physical location. |
Link | System-generated, protected field. Value is always 1. |
Interface Type | System-generated, protected field. Identifies the card type. |
Digital Link Descriptor | Enter a descriptor number that references an entry in the Digital Link Descriptors form where the characteristics of the digital link are defined. The maximum Descriptor Number is 16. | Blank
Resilient Link | Identifies a resilient T1/E1 link (see below). | 1
Comment | Enter up to 24 characters to describe the link (optional). | Blank

### Fields for T1/E1 Trunk Resiliency

After you assign a Digital Link Descriptor to a Universal T1 or Universal E1 interface, the following fields are available to allow you to enable T1/E1 trunk resiliency.

NOTE: Refer to the Resiliency Guide for instructions on how to install, configure, troubleshoot, and maintain T1/E1 trunk resiliency.

Parameter | Description
Resilient Link | This check box applies to T1/E1 links only. Select this check box to enable T1/E1 trunk resiliency for this link. You must enable this option on both the primary and secondary controllers. To support this feature, both the primary and secondary controllers must have 3300 ICP Release 7.0 or later software.
Resilient Link ID | On the primary controller, select a link identifier (1 to 4) for the primary link. This link ID must match the link ID that you assign to the secondary link. The link ID must be unique on the primary controller. To simplify the configuration, make the link ID the same as the module ID on the primary controller. On the secondary controller, assign the link with the same link ID that you programmed on the primary controller.
Primary Network Element | This field identifies the primary controller for a resilient T1/E1 trunk. The T1/E1 trunk from the PSTN connects to the T1/E1 Combo card in the primary controller. A resilient link connects the T1/E1 Combo MMC module in the primary controller to the standby T1/E1 MMC in the secondary controller. Select the system name of the primary controller from the drop-down list. The drop-down list contains the names of all the system elements that you have programmed in the Network Elements form. You must program this field on both the primary and secondary controller: Log into the System Administration tool of the primary controller and set this field to the system name of the Local controller. Set the Secondary System Name field (described below) to the name of the secondary controller that contains the standby T1/E1 MMC. Log into the System Administration tool of the secondary controller and set this field to the system name of the primary controller. Then set the Secondary System Name field to the system name of the Local controller. NOTE: The link for the primary controller must be provided from a T1/E1 Combo MMC. You can only modify this field if the "Resiliency Link" option (see above) is set to "Yes".
Secondary Network Element | This field identifies the secondary controller that provides the backup T1/E1 link for the primary controller. Select the system name of the secondary controller from the drop-down list. The drop-down list contains the names of all the system elements that you have programmed in the Network Elements form. If the primary controller (identified in the "Primary System Name" field above) fails, a bypass relay in the T1/E1 Combo MMC transfers support for the link to the T1/E1 MMC in this secondary controller. You can install either a T1/E1 Combo MMC or a T1/E1 Dual MMC in the secondary controller.