Some performance trade-offs associated with ATM fixed-length vs. variable-length cell formats

The authors compare asynchronous transfer mode (ATM) fixed-length-cell (FLC) versus variable-length-cell (VLC) formats with regard to memory requirements, delays, and efficiency considerations. In particular, they develop models for the comparison of these formats at an access multiplexer. Results show that at moderate outgoing link utilizations, the memory requirements for an FLC format are less than those for a VLC format. However, at higher outgoing link utilizations, the opposite is true, due to the inherent efficiency advantage of a VLC format. At moderate outgoing link utilizations, delays for short messages are found to be comparable. However, at higher outgoing link utilizations, a VLC format has an edge for short messages because of the efficiency advantage. It is concluded that the performance differences found here do not overwhelmingly favor either an FLC or a VLC format, and thus it is important to factor in other issues as well