ATM Adaptation Layer 2 (AAL2) is an Asynchronous Transfer Mode (ATM) adaptation layer, used primarily in telecommunications; for example, it is used for the Iu interfaces in the Universal Mobile Telecommunications System, and is also used for transporting digital voice.
AAL2 is a variable-bitrate connection-oriented low-latency service originally intended to adapt voice for transmission over ATM.
AAL2 is further separated into two sub-layers that help with the mapping from upper-layer services to ATM cells.
When the transmission is ready, the CPS packets are all multiplexed together into a single cell and transported over standard ATM network infrastructure.
[citation needed] Efforts to improve Ethernet networks are in a sense trying to reinvent the wheel à la ATM.
[citation needed] AAL2 is one example of a useful benefit of ATM, as a general standard for Layer 2 protocols.
The data from byte 1 ... (STF+1), would be the straddled remainder of the previous ATM cell's final CPS packet.
The format for the 1 byte STF at the beginning of the ATM cell is: The Offset Field carries the binary value of the offset, in octets, between the end of the P bit and the start of the CPCS-PDU Payload.
The Parity bit is used to detect error in the OSF and SN fields.
that needs to be done for standard AAL2 either is too strenuous, is unsupported, or requires too much overhead (i.e. the 1 byte of STF) from the internal system's point of view.
Most computer chips do not support AAL2, so stripping this layer away makes it easier to interwork between the ATM interface and the rest of the network.