Resumo em Inglês:

We model and simulate stochastic traffic based on two established statistics: marginal distribution and autocorrelation function. Although apparently equivalent to each other in these aspects, the three different synthetic models produce notably different behavior in a G/D/1/<FONT FACE="Symbol">¥</FONT> queue. As an alternative modeling strategy, we measure the log-moment generating function of the synthetic models. Our results indicate that recent works related to Effective Bandwidth functions may provide the discriminatory statistic required to explain the noted inconsistency.

Resumo em Inglês:

Recent advances in network technologies have far outpaced our abilities to effectively manage and engineer them. The fundamental challenge in the traffic management of these new and emerging networks is to describe, analyze and control the complex traffic flows they carry in ways that can be applied in practice. Our approach for tackling this problem is experimental in nature and starts with collection and analysis of high-resolution traffic traces from working networks. Traffic models that can accurately and adequately describe these complex flows are devised based on the measurement analyses, which then lead to the development of appropriate and practical traffic management methods. This paper reports on our experiences in analyzing a large number of traffic traces collected from a wide range of network technologies including Ethernet, ISDN packet, CCS, Internet, Frame Relay and ATM. We first describe the challenges in collecting, mining and filtering traffic traces from high-speed networks. Lessons learned from these efforts are then reported. Specifically, we discuss the choice of traffic models and the issues of traffic characterization and performance modeling from various viewpoints: i) aggregate versus individual traffic; ii) user session versus link layer traffic; and iii) user application versus network management traffic. The discussions are given so that the appropriate traffic models can be chosen in different scenarios, and subsequent traffic management methods can be developed and applied to these high-speed networks in practice.

Resumo em Inglês:

A closed loop rate based feedback control to support ABR service has been defined. In this approach the network at periodic intervals informs all transmitting sources the maximum rate at which the sources are allowed to transmit. For the scheme to be successful in that the network utilization is high and fairness is ensured for all competing users, it is imperative that all sources conform to the maximum rate at which they are allowed to transmit. To ensure the goals of ABR service are satisfied, especially in public networks, it is essential to police sources and penalize violating sources when deemed necessary. In this paper we investigate the effect of misbehaving or violating users on the network performance and the effectiveness of policing such sources.

Resumo em Inglês:

We consider a controlled queuing model and derive the corresponding Markov decision process for simple G/M/1 call admission controller. As an application of the controlled queuing model, we look into an optimal resource management problem arising in the context of multiservice cellular network with reuse partitioning. In particular, we consider a channel borrowing scheme between zones in two-zone reuse partitioning in a two-class cellular network and investigated the performance of various channel borrowing policies via simulation. We also introduce the simulator developed for controlled queuing systems. Most importantly, we demonstrate that Markov decision processes are well suited to this kind of optimization problem.

Resumo em Inglês:

Mobile access remains limited by relatively short battery power lifetime, expensive wireless bandwidth and areas with difficult or no continuous communication coverage. It is believed that as many as 70% of laptop users would operate in planned or non planned disconnected mode. Although existing approaches have led to implementing disconnected mode operation within applications, we chose to introduce changes to a mobile extension of the Internet transport protocol. We show through simulation that this protocol performs better than TCP. In order to evaluate disconnection parameters including disconnection and inter-disconnection times, a performance study of disconnection is presented. Finally we argue that disconnection is an important service and should therefore be considered as a Quality of Service (QoS) parameter to be negotiated among mobile and fixed communication entities.