Optimal buffer allocation in ATM switches by effective cell loss

• Authors: David S. Ahn;Myung J. Lee
• Venue: Journal of High Speed Networks
• Year: 1997

One of the important issues in an ATM switch design is how to allocate the given buffer budget to ensure compliance with negotiated traffic contracts of each ATM connection. This problem owes mainly to the conflicting buffer requirements of different QoS parameters, such as cell loss, cell transfer delay, and cell delay variation. For example, increasing the buffer size of a connection at a switch may reduce cell loss due to buffer overflow, but the benefit of adding buffers possibly causes an excessive queueing delay due to increased buffer sizes. In this paper, such trade-off issue in buffer allocation for different QoS requirements at a switch are quantified by a single nodal QoS parameter called Effective Cell Loss (ECL), in which both cell loss due to buffer overflow and cell loss due to excessive delay are properly integrated. The immediate benefit, among many others, of imposing ECL at switches is an optimal buffer allocation resulted by the conflicting buffer requirements of cell loss and cell delay parameter. Consequently, given the acceptable cell loss probability, the maximum cell delay tolerance, and the fixed buffer budget at an ATM switch, an optimal buffer allocation is found by minimizing ECL. Therefore, ECL is an effective QoS parameter that provides not only the most faithful way to comply with negotiated traffic contracts but also an optimal buffer allocation for a given buffer budget at a switch. Furthermore, we present the effectiveness of using ECL at a switch under nonuniform traffic arrival.