Multifunction Switch User Guide

Chapter 1 Overview
Avaya M770 M-ACCF/SF ATM Access Modules User’s Guide 15
Network Layer Concepts — ATM & ATM Adaptation
This Section describes the following concepts behind the network layer architecture
of a typical ATM network:
• The Layered Network Architecture
• ATM Adaptation Layer (AAL)
• Asynchronous Transfer Mode (ATM) Layer
•Physical Layer
The Layered Network Architecture
Asynchronous Transfer Mode (ATM) is one part of the layered network architecture.
This architecture is shown in Figure 1.8.
Each of the layers is discussed in turn; starting with the Upper Layer and working
down to the Physical Layer.
Figure 1.8 Network Layer Architecture
ULP PDUs
AAL5 PDUs
LAN Emulation
Frames
ATM Cel l s
SONET or SDH
med i a
PDUs
Protocol Data Units
Key
frames
Logical flow
Physical flow