3Com CoreBuilder 9000, User Manual

Page: 311 / 468

ATM Layers 311
ATM Adaptation
Layer (AAL)
The ATM Adaptation Layer is the standards layer that allows multiple
applications to have data converted to and from the ATM cell. There are
five AAL types. The AAL performs Segmentation and Reassembly (SAR)
on cells. It formats data into the 48-byte ATM cell payload, in effect
adapting applications to the cell-based ATM layer. When the ATM cells
reach their destination, they are reconstructed into higher-level data and
transmitted to the respective local devices. The AAL runs from end-system
to end-system and is transparent to the ATM network. For more
information, see “ATM Adaptation Layer (AAL)” on page 442.
Operation & Maintenance (OAM)
The Operation and Maintenance (OAM) group of network management
functions that provide network fault indication, performance
information, and diagnosis functions. For further information, see
“Operation and Maintenance (OAM)” on page 440.
For more information about the ATM layer and ATM cell structure, see
“ATM Layer” on page 438.