Voice Over IP

VOICE OVER ATM (VoATM)

The ITU-T has issued a draft recommendation on the ATM Adaptation Layer type 2 (AAL 2). It is published in ITU-T I.363.2. The concept of AAL 2 is to provide a mechanism for sending small packets (such as voice, since AAL 2 targets packet telephony) over an ATM network in a manner that ensures small delay. AAL 2 supports the multiplexing of multiple connections into one cell, thus avoiding the unattractive aspect of sending cells through the network that are partially filled. The connections are called LLCs, for logical link connections.

AAL 2 supports the multiplexing of variable length packets, a service that is quite important in accommodating to variable bit-rate coders and silence compression. Indeed, a fixed-length ...