TABLE OF CONTENTS ATM is a connection-oriented packet network. Because ATM services are provided based on connections, it is, in general, easier to provide QoS in ATM networks than in the connectionless IP networks. In a nutshell, QoS in ATM networks is provided by specifying the performance requirements for the requested logical connections along with the amount of bandwidth needed to meet the pre-specified performance level and administering a Connection Admission Control (CAC) to make sure that the performance of the current connections are not degraded by adding new connections.
After a brief discussion of the genesis of ATM, this chapter discusses the following topics:
ATM protocols
ATM virtual connections
ATM traffic descriptors
ATM QoS parameters
ATM service categories
ATM Connection Admission Control
ATM was developed to provide high-speed integrated services with a single infrastructure for data, voice and video. The main driving force behind the ATM development was the deficiency of ISDN in meeting this need. ISDN was considered inadequate to meet the needs of multi-media traffic. For example, ISDN Basic Rate Interface (BRI) operating at 128 kb/s and Primary Rate Interface (PRI) operating at 1.5 Mb/s were both insufficient for broadcast-quality video.
| ATM Chronology | |
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| Mid 1980's | Fundamental aspects addressed: fixed-length "cells" |
| 1989 | CCITT key standards agreements |
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| 1990's | CCITT (i.e., TTU-T) |
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| ATM Forum |
