Standards for Optical Networking

Several important new standards for optical networking were adopted by the Geneva-based International Telecommunication Union (ITU) in November.

The new standards provide the ability to combine multiple client signals within a single wavelength to maximize network use and cost-effectiveness while still allowing switching at the optical transport network (OTN) service rates of 2.5G, 10G and 40G bit/sec. They also specify optical equipment functions such as performance monitoring, fault isolation and alarming.

While the following ITU standards are primarily aimed at companies that produce optical networking hardware and software, it behooves IT managers to be aware of them as well.

  • G.872 (revised) -- Architecture of OTNs: The new specification includes (among other features) the ability to do time division multiplexing of signals carried on the OTN.
  • G.709 (amended) -- Interfaces for Optical Transport Networks: Amended to describe the mappings for time division multiplexed signals in OTNs, as well as extensions to allow even higher bit/sec. rate signals to be carried using virtual concatenation.
  • G.798 -- Characteristics of Optical Transport Network Hierarchy Equipment Functional Blocks: Specifies OTN equipment, including supervision, information flow, processes and functions to be performed by OTN equipment.
  • G.8251-- The Control of Jitter and Wander Within the Optical Transport Network: Specifies parameters that relate to the variability of the bit/sec. rate of signals carried over the OTN.
  • G.7041/Y.1303 -- Generic Framing Procedure: Specifies interface mapping and equipment functions for carrying packet-oriented payloads, including IP/PPP, Ethernet, Fibre Channel and Escon, over the OTN.
  • G.7710/Y.1701 -- Common Equipment Management Function Requirements: A generic equipment management recommendation.
  • G.874 -- Management Aspects of the Optical Transport Network Element: Specifies applications, functions and requirements for managing optical networking equipment utilizing an operations support system.
  • G.874.1 -- Optical Transport Network Protocol-Neutral Management Information Model for the Network Element View: Provides a means to ensure consistency among the models for OTN equipment, including the Common Management Information Service Element, Common Object Request Broker Architecture and Simple Network Management Protocol.
  • G.7712/Y.1703 -- Architecture and Specification of Data Communication Network: Allows the use of Internet Protocol and Open System Interconnection protocols and supports new services such as Automatic Switched Transport Networks through communications among the transport plane, the control plane and the management plane.

Non-ITU Standards

Besides the ITU, other standards bodies have also adopted important standards in optical networkings.

ANSI T.105 -- Synchronous Optical Network (Sonet) is a packet-switched network transport protocol using optical systems. Sonet has been adopted in the U.S., Japan and Australia, and Synchronous Digital Hierarchy is used throughout the rest of the world. Sonet defines multiple carrier bit/sec. rates, termed Optical Carriers (OC) levels. Each OC level is a multiple of the identifying number with the base rate.

Fiber Distributed Data Interface (FDDI) is a fiber-based networking standard specified by the ANSI X3T9.5 committee. It uses a dual counter-rotating parallel ring topology up to a distance of 100km and a token-passing protocol for redundancy and efficiency. It operates at a data rate of 100M bit/sec. It was intended as a backbone network, but high bandwidth demands led it to be adopted on LANs. It has a lesser cousin, the Copper Distributed Data Interface, that uses the same design and protocol except that it uses copper wires and operates over short distances.

Fibre Channel is specified in ANSI X.3230-1994 and ISO 14165-1. Its primary goal is to provide high-performance connectivity to LANs, data storage systems and computer peripherals. It supports protocols such as IP, SCSI and Asynchronous Transfer Mode Adaptation Layer 5 and allows the use of copper media found on existing networks. Its operating data rates are multiples of 133M bit/sec.

Fibre Channel is designed for scalable connectivity on an enterprise or institution and is expected to replace SCSI as a distributed storage interface for disk arrays and storage-area networks.

Copyright © 2002 IDG Communications, Inc.

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