Nortel Networks 8000 - Manual (Page 390)

10 Low-speed ATM configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
Figure 10-1 ATM protocol model
The AAL is responsible for forwarding the information between the ATM Layer and the upper
layer protocols. The following are the four types of AAL: AAL1, AAL2, AAL3/4 and AAL5.
Each of these supports certain special services. Most of the ATM equipments use AAL5 to
support the data communication service.
The ATM also has the QoS mechanism. For details, refer to the Nortel Secure Router 8000
Series Configuration Guide - QoS.
10.1.2 ATM interface
Classification based on functions
Based on the functions on the network, you can classify the ATM devices and interfaces into
the following two types:
• The user device is the Data Terminal Equipment (DTE), and the corresponding interface
type is DTE.
• The user provides the Data Circuit-terminating Equipment (DCE) access device
belonging to the network device and the corresponding interface type is DCE.
Classification based on physical media
The ATM physical layer lies at the bottom of the ATM protocol reference model. It is not
dependent on transmission mechanism and transmission rate. The ATM physical layer
transmits valid cells and corresponding timing signals between the upper layers and the
transmission media.
SR8000 supports several types of ATM interface including the following:
10-4 Nortel Networks Inc. Issue 5.3 (30 March 2009)