|AAL5, ATM Adaptation Layer 5|
AAL5 adapts multi-cell higher layer PDUs into ATM with minimal error checking and no error detection.
AAL5 is the adaptation layer for UNI signaling, ILMI, PNNI signaling, and for IP PDUs. It is the most widely used AAL type to date. AAL5 requires two distinct processes. The first is the encapsulation, on the transmit side, and de-encapsulation, on the receive side, of the higher layer PDU into the AAL5 CPCS PDU which requires the computation of the length and the CRC-32. The time required for this process depends on whether the CRC-32 computation is done on the interface (on-board) or in machine central memory (in core). On-board computation should produce only a small, constant delay; however, in core computation will produce variable delay, which will negatively effect TCP RTT computations. The second process is segmentation and re-assembly.
[RFC 2364] PPP Over AAL5.
[RFC 2684] Multiprotocol Encapsulation over ATM Adaptation Layer 5.
[RFC 3355] Layer Two Tunnelling Protocol (L2TP) Over ATM Adaptation Layer 5 (AAL5).
[RFC 1483] Multiprotocol Encapsulation over ATM Adaptation Layer 5.
[RFC 1626] Default IP MTU for use over ATM AAL5.