Wide-Area Networks - CCIE Routing and Switching Exam Certification Guide - page 221

ATM Reference Model Figure 5-14

Management Plane

Control Plane

User Plane

Class A
Constant
bit rate
(DS circuit
emulation)

Class B
Variable
bit rate
(VBR voice
and video)

Class C
Connection
oriented
services
for data

Class D
Connectionless
services
for data

Signal and control

Management
entity

AAL 1 AAL 2 AAL 3/4

AAL 5

Adaptation Layer

AAL convergence sublayer

Segmentation and reassembly sublayer

ATM Layer (service independent, cell formatting, header generation)

Physical Layer Transmission convergence sublayer

Physical medium dependent sublayer

The control plane supports both PVCs and SVCs. The control plane enables the exchange of
signaling information between ATM endpoints to establish call setup. It is responsible for call
setup, maintenance, and call removal of switched VCs.

AAL

The AAL is responsible for adapting the information provided by the user plane to a form that
the ATM layer can use. The AAL identifies five categories of traffic based on the following
requirements:
•

End-to-end timing relationship

•

Bit arrival rate

•

Connection requirements

Traffic that is time-sensitive, connection-oriented, and arrives at a constant rate, such as DS1 or
DS3 circuit emulation, uses AAL1,which includes a time stamp in the cell.