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This chapter provides an overview of ATM standards bodies, their responsibilities, and the history of ATM. It also outlines the major ATM standards and describes the ATM protocol layers.
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Chapter Objectives • After completing this chapter you will be able to: • List the ATM standards bodies • Outline the responsibilities of the ATM Forum • Describe briefly the history of ATM • Outline the major ATM standards • Describe the ATM protocol layers
ATM Standards Bodies • Main international standards organisation for ATM is the ITU-T • ITU-T decision-making is relatively slow • Based on absolute majority voting
ATM Forum • Formed in 1991 • Committee of companies • ATM Products, Software, Test and Service Providers • Developed early standards via White Papers • Single technical committee ensures integrity • Works closely with international standards bodies (IETF, ITU-T, ANSI etc.) • Develops faster • based on 2/3 majority voting
ATM’s History • 1983 - First ATM papers published • 1987 - ITU-T selects ATM for B-ISDN • 1990 - ITU-T issues 13 recommendations • 1992 - First ATM LANs installed • 1993 - First ATM WANs installed
API SIG AMS CES SMDS FRS LE MN Network Lan ATM UNI Multi-Media Nx64K SIP CLS FR SSCS Man’mnt Emulation ATM UNI V4.0 Conversational V4.0 Signalling Signalling T1 Video on Protocol API Demand SSCF E1 Broadcast SSCOP AAL5 AAL1, AAL3/4 AAL5 AAL5 AAL5 AAL1 AAL-API CPCS AAL5 CPCS CPCS Null AAL SAR SAR SAR SAR SAR SAR SAR API End-to-End ATM Performance Objectives (I.350) Minimum Quality of Service Values Physical Layer ATM’s Services Aspects Work Groups
Published Recommendations • From the ATM Forum: • A major work is the user-network interface specification • Known as UNI 3.1, 4.0, 4.1 (1999) • UNI 3.1 is a collection of specifications that apply to the user-network interface • UNI 4.0 and later specifications and revisions are published as individual papers • The current list of approved papers and work in progress is available at: www.atmforum.com
The International Standards • Published by ITU-T • I.113 B-ISDN Vocabulary • I.121 Broadband Aspects of ISDN • I.150 B-ISDN ATM Characteristics • I.211 B-ISDN Service Characteristics • I.311 B-ISDN Network Aspects • I.321 B-ISDN Protocol Reference Model • I.327 B-ISDN Functional Architecture • I.361 B-ISDN ATM Layer Specification • I.362 B-ISDN ATM Adaption Layer • I.413 B-ISDN User-Network Interface • I.432 B-ISDN UNI Physical Layer Specification • I.610 OAM Principles of B-ISDN Access • Q.2931 B-ISDN Access Signalling
ATM Protocol Layers Higher layers CS Adaptation Layer SAR Layer two ATM Layer TC Layer one Physical Layer PMD
Management software Signalling software Interfaces Fabric Input/output buffers scheduler, mappings High-speed switching ATM Switching Nodes