ATM AAL Layers-Difference between AAL1,AAL2,AAL3,AAL4,AAL5

Refer Following links to subtopics on ATM tutorial:
ATM Network Architecture & Interfaces ATM Protocol Stack ATM services ATM Switch ATM Call Flow ATM vs STM ATM vs TDM ATM versus Frame Relay ATM AAL Layer Types

This page compares ATM protocol layers AAL Type 1 to 5 i.e. AAL1, AAL2, AAL3, AAL4, AAL5 and mention difference between AAL1, AAL2, AAL3, AAL4, AAL5 ATM protocol layers. ATM Adaptation layers are classified based on their support for various service classes as well as following parameters:
• Timing between source and destination (required or not required)
• Bit rate (constant or variable)
• connection mode (whether connection oriented or connectionless)
• AAL service Classes- A/B/C/D

Fig-1:ATM AAL Layers

AAL Layer in ATM is divided into two sublayers viz. Convergence Sublayer (CS) and Segmentation and Reassembly Sublayer(SAR) based on functionality of AAL layer. The function of ATM Adaptation layer in ATM protocol stack are summarized below:

CS sublayer performs following functions:
• management of lost and wrongly delivered ATM cells
• Timing recovery
• Interleaving

Fig-2:ATM Protocol Stack

SAR sublayer performs following functions:
• Fragmentation of bit stream from upper layers into size equal to ATM cells for transmission to ATM layer in the stack.
• Reassembly of ATM cells into bit stream for delivery to upper layers.

The figure-2 depicts ATM protocol stack mentioning AAL layer. Refer ATM Protocol Stack➤.