1. 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

2. 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

3. 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

4. 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

5. ATM’s Services Aspects Work Groups

6. 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

7. The International Standards Published by ITU-T –I.113B-ISDN Vocabulary –I.121Broadband Aspects of ISDN –I.150B-ISDN ATM Characteristics –I.211B-ISDN Service Characteristics –I.311B-ISDN Network Aspects –I.321B-ISDN Protocol Reference Model –I.327B-ISDN Functional Architecture –I.361B-ISDN ATM Layer Specification –I.362B-ISDN ATM Adaption Layer –I.413B-ISDN User-Network Interface –I.432B-ISDN UNI Physical Layer Specification –I.610OAM Principles of B-ISDN Access –Q.2931B-ISDN Access Signalling

8. ATM Protocol Layers ATM Layer Physical Layer Adaptation Layer TC SAR CS Layer two Layer one Higher layers PMD

9. ATM Switching Nodes Interfaces Fabric Input/output buffers scheduler, mappings High-speed switching Management software Signalling software