dtj v03-02 1991

This document is the Spring 1991 issue (Volume 3, Number 2) of the Digital Technical Journal, published by Digital Equipment Corporation. The issue focuses entirely on the Fiber Distributed Data Interface (FDDI), highlighting Digital's comprehensive approach to developing and implementing this high-speed local area network (LAN) technology.

Key themes and topics covered across the articles include:

1. FDDI Overview: Discusses Digital's decision to adopt FDDI as a second-generation LAN, emphasizing its tenfold bandwidth increase over Ethernet (100 Mbps), consistency with IEEE 802 LANs, and ANSI standardization. It covers FDDI's operational theory (timed-token protocol, dual fiber-optic ring) and its role in Digital's network architecture.
2. Physical Layer Development: Details the design and implementation of FDDI's physical layer hardware, including custom VLSI chip sets (using ECL and CMOS), the distributed clock scheme, optical link design (1300nm LED for 2km), and mechanisms for controlling and isolating errors (e.g., elasticity buffer, Link Error Monitor).
3. Data Link Development: Explores the Media Access Control (MAC) protocols, including frame transmission and reception, ring initialization, fault detection/recovery, and address recognition. It highlights the design and verification of Digital's custom chips (Ring Memory Controller, MAC, Content Addressable Memory) that implement these functions.
4. Common Node Software (CNS): Describes a reusable software implementation developed by Digital to manage FDDI station management (SMT) protocols and chip sets. CNS ensures consistent behavior across various Digital FDDI products, handles physical and logical connections, and facilitates interoperability.
5. FDDI Products:
   • DECbridge 500: An Ethernet/802.3-to-FDDI bridge designed to seamlessly connect different LAN types, handling challenges like frame format translation and fragmentation for large IP packets.
   • DECconcentrator 500: A product enabling the "dual ring of trees" topology for FDDI, enhancing network availability, manageability, and supporting structured wiring in office environments. It incorporates fault tolerance and link error monitoring.
   • ULTRIX FDDI Controller 700: Details the implementation of a host networking subsystem for RISC-based DECstation 5000 workstations, integrating high-speed FDDI communication directly into the ULTRIX operating system, with a focus on performance optimization.
6. Network Management (DECelms): Introduces Digital's software for managing FDDI and Ethernet extended LANs. It provides advanced features such as automatic fault detection, device discovery, performance monitoring, and ring mapping, serving as both a network management tool and a development aid.

The document emphasizes Digital's comprehensive engineering process, including extensive simulation, verification, and multi-vendor interoperability testing, to deliver high-quality, reliable FDDI products amidst evolving standards and tight development schedules.