Maintenance Operations Protocol Functional Specification Version V4.0.0

This document specifies Version V4.0.0 of the DECnet Maintenance Operations Protocol (MOP), published in June 1992.

MOP provides low-level remote maintenance functions for DECnet networks, designed to operate independently of higher-level software and directly utilizing data link services. Its primary functions include:

1. Communications testing: To determine if the data link path is operative.
2. System console access: For tasks like system identification, reading data links, and booting systems.
3. System load/dump: For copying processor memory to or from a remote system.

MOP operates on a client-server model, where "requesters" initiate maintenance operations and "servers" respond. It resides in the Digital Network Architecture (DNA) Network Management Layer and interfaces directly with various Data Link Layers such as DDCMP, HDLC, LAPB, CSMA/CD (Ethernet/IEEE 802.3), and FDDI.

The protocol's operations are managed through a structured set of entities:

• A central MOP module.
• Client subentities that store default parameters for requesters (Dump/Load, Console, Loop, Test/Query) and servers.
• Circuit subentities that describe the data link circuits MOP uses and define which MOP services are enabled on them.
• Operation subentities that are dynamically created to monitor the state of MOP operations in progress.
• Station subentities (for LAN circuits) that record information from discovered network stations via System ID messages.

Key MOP directives include Loop (for testing communication paths), Load (for downline loading system images), Boot (for remote system initialization), Test (for IEEE 802.2 tests), and Query (for IEEE 802.2 XID exchanges), along with standard management directives like Create, Delete, Enable, and Disable for MOP entities.

The design emphasizes minimal state, processing, and memory efficiency, and supports compatibility with previous MOP versions (V3.1.0). It is explicitly stated that system security is not a primary goal for these low-level functions.