MOP registry

This document, the "MOP registry," published by Digital Equipment Corporation (DEC) on March 22, 1993, is a comprehensive list of predefined MOP (Maintenance Operation Protocol) code assignments for the DECnet Digital Network Architecture.

Its primary purpose is to provide the official registry of codes for:

1. Communication devices: Various network interfaces, adapters, multiplexers, and bridges used within DEC's network environment (e.g., DEUNA, DELQA, LANBridge, VAXmate).
2. Data link types: Different network technologies and protocols (e.g., CSMA-CD, DDCMP, LAPB, HDLC, FDDI, Token-passing Ring).

These assigned values are referenced in DECnet's interfaces and message definitions. The registry explicitly states that codes for products under development are not included, and any unassigned values are reserved for future use. It also contains notes on specific historical or alternate code assignments for certain devices and clarifies the relationship between data link types and "Circuit Type" codes.