scope:

This document covers maintenance of the Layer 2 (data-link-layer) and Layer 3 (network-layer) peer relationships between the exchange termination (ET) and customer equipment (see Figure 1). The layer 2 and layer 3 peer relationships considered are signaling data on the D-channel, packet data on the D-channel, and packet data on a B-channel.

Although the required maintenance capabilities are described from the ET perspective, similar data-link- and network-layer maintenance capabilities may be provided in customer equipment implementing the Network Termination 2 (NT2), Terminal Equipment 1 (TE1), or Terminal Adapter (TA) functional groups.

Although the required maintenance capabilities are described with respect to customer access protocols (e.g., ITU-T Recommendations Q.931 and X.25), customer equipment may provide similar maintenance capabilities with respect to end-to-end protocols (e.g., ITU-T Recommendation V.120).

This standard uses the requirements defined in ITU-T Recommendation M.3640 for the D channel maintenance at protocol Layers 2 and 3. The packet B channel maintenance requirements are found in this specification.

Purpose

The purpose of this standard is to establish required capabilities for the maintenance and operations needed for the data-link layer (Layer 2) and network layer (Layer 3) associated with access to Integrated Services Digital Networks (ISDNs). This standard establishes needed maintenance functionality in customer and network equipment, particularly from the perspective of maintenance functionality available at the network boundary and from Operations Systems.

The principles and general maintenance strategies of ISDN management are applied to the maintenance of the data-link and network layers. In particular, the progression of maintenance tools used for trouble resolution would include continuous in-service monitoring, on-demand inservice monitoring, and - finally - out-of-service testing. In the context of data-link and networklayer maintenance, the maintenance capabilities should support the following:

• Clear distinction between transmission induced errors and protocol problems at Layers 2 and 3;

• Detection of high-protocol abnormality rates and service disruption caused by problems at Layer 2 or Layer 3;

• Identification of the type of trouble at Layer 2 or Layer 3; and

• The ability to isolate Layer 2 and Layer 3 troubles.