CAC investigation for video and data

Abstract

A key objective of ATM-based networks is to provide at the same time guaranteed QoS to real time and non-real time services. This calls for thoroughly engineered traffic control methods for those service categories as well as for the overall integration strategy. The main objective of this paper is to investigate CAC in an ATM testbed with real switches and as realistic traffic as possible. The used traffic is video (MPEG model based on traces) and data modelled as traditional on/off sources. The video traffic is given priority over the data traffic. To complement and verify the experiments, two simulation tools using as input the artificial MPEG models and the real traces have been developed. The CAC boundary for the nonpriority case has also been derived analytically. The experimental sources are modelled as discrete-time Markov sources. A matching method to avoid state space explosion for the superposition is applied on the source models.

Circulant matching method for multiplexing ATM traffic applied to video sources

“…This explains partially why in the analytical curve the number of sources that can be accepted is smaller than in the experiments, with a larger difference if more Asterix sources are involved. Analogous observations are found by simulation (Aarstad et al 1998).…”

“…Figure 2 compares the analytically derived 10-4 CAC boundary with the experimentally obtained one. As in the experiments, for a mix of two types of sources, the admission boundary is close to linear (Aarstad et al 1998). IT the points in Figure 2 are compared, it is seen that the analytical results are more conservative than the experimental results, with a larger deviation if the number of Asterix sources grows.…”

“…Those multiplexing experiments were performed in the framework of a CAC investigation for video and data and are reported in detail in (Aarstad et al 1998). The experiments are based on multiplexing, since the way to perform them is to change the traffic mix until a CLR below, but as close as possible to a fixed value is obtained.…”

“…For this, the method is applied to an MPEG source type model developed in (Helvic 1996). This model was used in a series of Connection Admission Control (CAC) experiments (Aarstad et al 1998) performed in the EXPERT project of the European Telecommunications research programme ACTS at the ATM testbed in Basle, Switzerland.…”

“…The CLR values resulting from the circulant matching method are compared with those obtained from a series of experiments (Aarstad et al 1998) performed within a European project in the ACTS programme, EXPERT.…”