Appendix D. Glossary
- AAL (ATM Adaptation Layer)
A service-dependent sublayer of the data link layer. The AAL accepts data from different applications and presents it to the ATM layer in the form of 48-byte ATM payload segments. AALs consists of two sublayers: Convergence Sublayer (CS) and Segmentation And Reassembly (SAR). AALs differ on the basis of the source-destination timing used, whether they use Constant Bit Rate (CBR) or Variable Bit Rate (VBR), and whether they are used for connection-oriented or connectionless mode data transfer. Currently, the four types of AAL recommended by the International Telecommunication Union's ITU-T are AAL1, AAL2, AAL3/4, and AAL5:
AAL1— Used for connection-oriented, delay-sensitive services requiring constant ...
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