Performance Analysis of the Dual Cell Spacer in ATM Systems

Abstract

In this paper we develop an analysis of the so-called Dual Cell Spacer. In contrast to a conventional spacer, which shapes a traffic stream only according to a given Peak Cell Rate, the Dual Cell Spacer takes into account the Peak Cell Rate as well as the Sustainable Cell Rate with the corresponding Burst Tolerance. The analysis is carried out in the discrete-time domain. Performance measures such as the cell rejection probability, the cell delay distribution and the cell inter-departure time distribution are derived. All results are of an exact nature. Numerical examples that compare the performance of the Dual Cell Spacer with that of a conventional spacer show a similar performance in terms of cell delay and cell loss for relatively small values of the Burst Tolerance. Using our analysis, both the Sustainable Cell Rate and the Burst Tolerance, which are used for traffic shaping in the Dual Cell Spacer, can be chosen adequately to achieve a given target cell rejection probability or cell delay, respectively, and to allow the network provider to obtain a high multiplexing gain.

Analytical models for the multiplexing of worst case traffic sources and their application to ATM traffic control.

“…However, among the resource allocation proposals, some presuppose the knowledge of parameters that are difficult to obtain and control, others require a great deal of calculations while others cannot guarantee the complete absence of network congestion. Furthermore, in order to have a CAC method that achieves the aforementioned requirements, it is necessary to use mechanisms of Traffic Shaping ( [28] and [80]) or Scheduling ( [34], [48] and [74]) that would bring additional cost to the designing of the network.…”

“…• Dual Cell Spacing: proposed by M. Ritter in [80], the Dual Cell Spacer takes into account the PCR as well as the SCR/BT. It has also been used to study the aggregation of VCCs in a VPC, see [81].…”

“…Since this method does not provide good BT tolerances for low rate connections, they propose a second method based on the dual spacer. The dual spacer, [80], is equivalent to two shaping devices operating in series. The first one enforces the cell stream to the SCR and BT and the second one to the PCR.…”

“…We have mentioned that a possible solution to the problems that may cause the multiplexing of WCT sources in the buffer occupancy is the use of traffic shaping techniques. The Spacer-Controller, [28], the Leaky Bucket shaping, [4], or the Dual Spacer, [80] or scheduling algorithms are different proposals to shape traffic. These mechanisms shape the traffic so that they can guarantee the absence of bursts in CBR traffic that enters the network.…”