On effectiveness of conditional admission control for IP QoS network services with REM scheme

Future IP QoS (quality of service) networks are aiming at differentiating transfer quality of packets belonging to different flows. For this purpose, a set of network services (NS) with different QoS objectives is defined and implemented in the network. To a NS a certain amount of network resources, i.e. dedicated link capacity with associated buffer size, is allocated. Moreover, the resources dedicated for one NS are not available for other NSs. Traditional approach for admission control algorithm corresponding to given NS takes into account current traffic conditions inside considered NS. This can lead to the situation, due to traffic fluctuations, that temporary overloaded NS cannot use the spare bandwidth from underloaded in this time other NSs. This paper describes a conditional admission control algorithm (C-AC), allowing us to admit new packet flow conditionally in the case where no available capacity inside a given NS. For conditionally accepted flow currently unused capacity, dedicated to other NS, is allocated. This can be done only in the case when QoS requirements for both the conditionally accepted flow and the flows in progress are satisfied. The conditions for effective using of C-AC algorithm are discussed in the paper, like characteristics of NS borrowing and lending capacity and their current traffic load. To show potential benefits of the approach, exemplary numerical results are included, corresponding to hypothetical NSs using REM (rate envelope multiplexing) scheme.