Journal of High Speed Networks - Volume 9, issue 2

Authors: Rosenberry, Robert D. | Sidhu, Deepinder P.

Article Type: Research Article

Abstract: Telecommunications networks are evolving from rigid, hierarchical time division multiplexed networks into Broadband‐ISDN networks based upon Asynchronous Transfer Mode infrastructures. As the transport networks change, the signaling network architectures must also progress. Currently, signaling network architectures are optimized for operation over point‐to‐point circuit switched networks. In this paper, we examine the current hierarchical signaling network architecture and propose two alternatives for use in B‐ISDN environments – a flat model and a hybrid model combining features from the other two models. Analysis of the network architectures is performed using a discrete event simulator for ATM networks with additional components modeling the …operation of telecommunications networks. Show more

Citation: Journal of High Speed Networks, vol. 9, no. 2, pp. 57-66, 2000

Authors: Kidambi, Jayakrishna | Ghosal, Dipak | Mukherjee, Biswanath

Article Type: Research Article

Abstract: Fair allocation of available bandwidth to competing flows is a simple form of quality of service (QoS) that can be provided to customers in public networks. A number of packet‐scheduling and buffer‐management techniques have been proposed in the literature to achieve this goal efficiently. However, the complexity of the existing algorithms prevents a high‐speed implementation with the current state of router technology. We propose a computationally simpler mechanism based on token‐bucket policing to achieve almost equal bandwidth allocation for a set of competing flows. The proposed method adjusts the token‐bucket threshold dynamically and measures the instantaneous arrival rate of flows. …It uses this information to decide whether or not to admit a packet arriving at the network edge. With minor modifications, our framework can be used in a variety of practical network environments ranging from the Internet to virtual private networks (VPNs) over Frame Relay. We present a detailed simulation study that evaluates the performance of our algorithm. The simulation results indicate that DTB is fair, efficient, and robust. Show more

Citation: Journal of High Speed Networks, vol. 9, no. 2, pp. 67-87, 2000

Authors: Biswas, Subir K. | Sengupta, Bhaskar

Article Type: Research Article

Abstract: For multirate wireless ATM traffic, the first part of the call admission process is to determine whether to admit calls as long as bandwidth is available or to deny admission to a call of a particular class even if there is enough bandwidth available, in the hope of admitting calls of some other class later. A second part of the process is to determine if the quality of service requested by the call can be met. A scenario in which the first part is particularly important is when the blocking probability requirements for different classes is different. In this paper, …we consider four policies to determine the circumstances under which calls of different types are admissible. For each of these policies, we show how to compute the blocking probabilities. For three of these policies, the blocking probabilities can be found by using results from product form networks. For the fourth, we provide an approximation which works extremely well in practice. We also formulate a non‐linear programming problem which attempts to determine the parameters of the admissibility policies in such a way to maximize the call arrival rates while keeping the blocking probabilities under specified bounds. We provide an algorithm for solving the non‐linear programming problem and use this as a basis for comparing the policies. We show that under some circumstances, it is possible to improve the system throughput by as much as 35% by a suitable use of the admissibility policies. This improvement in throughput is particularly important in wireless ATM networks, supporting high rate multimedia traffic because of the inherent limitations in bandwidth availability. Show more

Citation: Journal of High Speed Networks, vol. 9, no. 2, pp. 89-99, 2000

Authors: Giordano, Silvia

Article Type: Research Article

Abstract: A shaper is a system that stores incoming bits in a buffer and delivers them as early as possible, while forcing the output to be constrained with a given arrival curve. A shaper is time invariant if the traffic constraint is defined by a fixed arrival curve; it is time varying if the condition on the output is given by a time varying traffic contract. This occurs, for example, with renegotiable variable bit rate (RVBR) services. We focus on the class of time varying shapers called time varying leaky bucket shapers; such shapers are defined by a fixed numbers of …leaky buckets, whose parameters (rate and bucket size) are changed at specific transition moments. We assume that the bucket levels are kept unchanged at those transition moments (‘no reset’ assumption). Our main finding is an input‐output characterisation for this class of time varying shapers. Then we apply it to the tradeoff in optimising the RVBR service, assuming that a perfect prediction of future traffic can be made. We provide two algorithms that solve the problem of finding, at any renegotiation, the parameters for a RVBR service, respectively when the knowledge of the input traffic is limited to the next interval (local optimisation problem) and when we dispose of the complete input traffic description (global optimisation problem). We compare, by means of simulation, the two resulting algorithms to study the validity of the local approach. We illustrate the impact of the ‘no‐reset’ assumption by analyzing on some examples the losses that occur when the source chooses the opposite approach, namely, the ‘reset’ approach. Furthermore we simulate the RVBR service versus the renegotiable constant bit rate (RCBR) service and illustrate that the RVBR approach can provide substantial benefits. Finally, we discuss the impact of the size of the renegotiation interval on the efficiency of the RVBR service. Show more

Citation: Journal of High Speed Networks, vol. 9, no. 2, pp. 101-138, 2000

Authors: Gouda, Mohamed G. | McGuire, Tommy M.

Article Type: Research Article

Abstract: We consider communication primitives that can be executed by an application process to exchange messages with another application process over a TCP/IP network. A communication primitive is called alert iff it satisfies two conditions. First, if during any execution of the primitive no failure occurs, then the execution completes successfully. Second, if during any execution of the primitive some failure occurs, then the execution is aborted and the process that initiated the execution is informed of the failure. Clearly alert communication primitives are useful in designing reliable distributed applications. We argue that the send primitive over TCP is alert, but …the receive primitive over TCP is not. Then, we propose three new receive primitives over TCP and show that each of them is alert. We also discuss how to implement these three primitives and compare their performance. Show more

Keywords: Distributed applications, fault tolerance, Internet, interprocess communication, reliability, Transmission Control Protocol

Citation: Journal of High Speed Networks, vol. 9, no. 2, pp. 139-150, 2000