10 th POLISH TELETRAFFIC SYMPOSIUM PSRT2003 ASSESSMENT OF TOKEN BUCKET PARAMETERS BY ON-LINE TRAFFIC MEASUREMENTS

The paper proposes a method for more precise evaluation of traffic descriptors than a user of QoS oriented packet network is usually able to declare during the pre-connection phase. The recognized approach for traffic characterization is the token bucket mechanism, described by two parameters: token accumulating rate and bucket size. Notice that the values of these parameters constitute a base for evaluation of the effective bandwidth (or an equivalent factor) and, as a consequence, determine the amount of resources the network should dedicate for handling the connection. The typical approach is such that the token bucket parameters are simply declared by the users during the preconnection phase. However, a user usually does not know a priori the correct token bucket parameters and has a tendency rather for over-dimensioning them. As a consequence, the calculated effective bandwidth is greater (sometimes significantly) than it is really required. In order to mitigate this problem, in this paper we propose a method based on the on-line monitoring of traffic, which allows us to obtain the minimum effective bandwidth. The method is investigated for the case the users submit the traffic to the network service aimed for handling non-real time variable bit rate traffic without any losses. In this case, the effective bandwidth value could be calculated e.g. by EMW [3] formula. Apart the theoretical considerations, the numerical results illustrating the effectiveness of the approach are also included

On Effectiveness of Conditional Admission Control for IP QoS network services with REM scheme

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 t