Switching algorithms and buffer management in asynchronous transfer mode networks

In this thesis, two different but related concepts in Asynchronous Transfer Mode (ATM) are discussed. Due to its multirate nature, ATM creates new problems in terms of switching and buffering. In the first part, the switching problems are investigated. The situation is rooted upon the multirate connections in a 'circuit-switching-like' environment. The multirate nature of ATM results in the loss of strictly nonblocking three stage space-division switches unless a 'speed-up factor' is provided between the outside ports and the internal links of the switch. To keep this factor to a minimum, call routing algorithms are considered as a possible solution. Several call routing algorithms are compared in terms of their blocking probability under various circumstances. A simple algorithm, named fixed priority routing algorithm, stands out among these, both in terms of simplicity and low blocking rate. Afterwards a bin packing model is used to investigate the reasons behind this. In the second part, buffer management in ATM nodes is considered. In the traditional sense, the burstier the traffic is, the higher, it was believed, the cell loss will be at a buffer into which a number of these sources are transmitting. It is shown that this is not always the case and under the circumstances defined - the worst-case model - other types of sources that output traffic that is less bursty might create higher cell loss than burstier sources. All sources considered are leaky-bucket controlled and stay within their contract limits with the network at all times. Initially greedy on-off source and the three-state source types are compared. After establishing that the comparison between these two in terms of cell loss rate is highly dependent on the size of the buffer being transmitted onto, other source types that might create even higher cell loss rates are searched for. One such characteristic group of sources is found and is presented