
Understanding ATM, ATM Router Redundancy, and OAM
308612-14.00 Rev 00
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Figure 1-4. B-ISDN ATM Protocol Reference Model
The following layers relate directly to how Nortel Networks routers support ATM:
• Physical layer
•ATM layer
• ATM adaptation layer (AAL)
Physical Layer
In a Nortel Networks Backbone Node (BN
®
) router, Intelligent Link Interface
(ILI) pairs provide access and processing. An ILI pair consists of a link module
and a processor module that work together to process and transmit information
over a network. Nortel Networks provides an ATM Routing Engine (ARE) link
module in conjunction with an ARE processor.
In addition, Nortel Networks provides a hub version of the ATM ARE ILI pair, the
Model 5782 ATM router. This single hub module, incorporating the ILI functions
of both the link module and processor module, resides in a System 5000BH
chassis. See Using the Model 5782 ATM Virtual Network Router for more
information.
The ILI pair and the Model 5782 ATM router are functionally identical, and you
configure them in much the same way. Unless otherwise noted, the remainder of
this guide treats the router ILI pair and the Model 5782 as if they were the same.
Higher protocol layer
ATM
adaptation
layer
(AAL)
Convergence sublayer (CS)
Segmentation and reassembly sublayer (SAR)
ATM layer
Transmission convergence sublayer
Physical medium dependent sublayer (PMD)
Physical
layer
(PHY)
ATM0003A
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