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INFOCOM '95. Fourteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Bringing Information to People. Proceedings. IEEE

Date 2-6 April 1995

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  • Proceedings of INFOCOM'95

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    Freely Available from IEEE
  • Author index

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  • Performance analysis of finite output-buffered multistage ATM switching fabrics

    Page(s): 16 - 23 vol.1
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    A new and accurate Markov chain model for evaluating the performance of multistage ATM switching fabrics with 2×2 finite output-buffered switching elements is proposed. By comparing the results obtained from the proposed model, existing models, and simulations, it has been shown that the proposed model is much more accurate than existing models in the presence of a non-uniform traffic in the switch. The results from existing models are unsatisfactory in the presence of an increased blocking in the switch arising due to a non-uniform traffic in the switch. On the contrary, the proposed model is very robust even under severe blocking inside the switch View full abstract»

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  • Optimal buffer sharing

    Page(s): 24 - 31 vol.1
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    Addresses the problem of designing optimal buffer management policies in shared memory switches when packets already accepted in the switch can be dropped (pushed-out). The goal is to maximize the overall throughput, or equivalently to minimize the overall loss probability in the system. For a system with two output ports, the authors prove that the optimal policy is of pushout with threshold type (POT). The same result holds if the optimality criterion is the weighted sum of the port loss probabilities. For this system, the authors also give an approximate method for the calculation of the optimal threshold, which they conjecture to be asymptotically correct. For the N-ported system, the optimal policy is not known in general, but it is shown that for a symmetric system (equal traffic on all ports) it consists of always accepting arrivals when the buffer is not full, and dropping one from the longest queue to accommodate the new arrival when the buffer is full. Numerical investigations show that under the optimal POT policy the loss probability of a port is insensitive to traffic fluctuations in the other port View full abstract»

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  • Efficient computation of end-to-end performance measures for multi-link ATM networks with multi-media traffic

    Page(s): 170 - 178 vol.1
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    In this paper, we provide: (a) An efficient method for simplifying MMPP source models, which can be used to solve multi-media queueing problems with complicated aggregate input traffic. The effectiveness of the method is verified through numerical examples. (b) An approximation algorithm for analyzing multi-link queueing networks with MMPP traffic sources and arbitrary configurations. In this algorithm, a queueing network is analyzed by decomposing it into individual queues, each with an arrival rate appropriately reduced by the packet dropping occurred in other queues. Each queue is then solved individually by using the simplified source models of (a) while the interdependencies with the other queues are accounted for through this reduced-load approximation. Any desirable end-to-end performance measure characterizing the quality of service (QOS) of the multi-media traffic can be calculated in this manner. The results obtained by the algorithm have been compared with simulation results, and the observed relative error is satisfactory View full abstract»

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  • On-line routing for permanent virtual circuits

    Page(s): 278 - 288 vol.1
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    The paper considers the problem of routing a set of permanent virtual circuit requests over a backbone network. Several factors make this routing problem complicated. Routing decisions must be made on-line without any knowledge of future request sets. Furthermore, frequent rerouting to correct inefficiencies that can result from the on-line routing decisions is not possible since rerouting creates a service disruption for the customer. Finally, the forward and reverse bandwidth of a virtual circuit must be routed over the same single path. Using an extensive set of simulations, the paper evaluates several different strategies for on-line permanent virtual circuit routing. The authors find that a strategy based on results in competitive analysis and ideas from combinatorial optimization consistently provides the best performance. The problem of admission control is closely related to the problem of routing. The paper also provides a theoretical lower bound that suggests that non-greedy admission control is a fundamental component of an efficient on-line permanent virtual circuit routing algorithm View full abstract»

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  • A generalized non-preemptive priority queue

    Page(s): 354 - 360 vol.1
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    In this paper, we analyze a generalized non-preemptive queue with two priority classes. When the server serves the low priority queue, up to l customers are served before the server returns to the high priority queue. We study the embedded Markov chain at departure epochs and obtain the transforms of the queue-length and sojourn-time distributions. From these transforms, it is easy to find the moments View full abstract»

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  • The effects of tuning time in bandwidth-limited optical broadcast networks

    Page(s): 138 - 145 vol.1
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    We consider the effects of tuning delay in optical broadcast networks. We show that for off-line scheduling these effects are small even if the tuning time is as large as the packet duration. In particular, we consider scheduling of random traffic with tunable transmitters and fixed-tuned receivers. We provide a lower bound to the completion time of any off-line schedule with an arbitrary number of wavelengths. We then describe a near-optimal schedule which is based on the principle of having idle transmitters tune to wavelengths just-in-time to start their transmissions. Stability and capacity issues in the transmission of real-time traffic are considered. We show that the scheduling problem admits a single stable equilibrium point, and point out how the traffic capacity of a broadcast network can be reached. We also consider the implications in connection-oriented networks View full abstract»

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  • The converging flows problem: an analytical study

    Page(s): 32 - 39 vol.1
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    When multiple systems are interconnected through a high-speed backbone network and communicate without resource reservation, under certain conditions a severe overload can appear at the destination system. This problem, called the converging flows problem, can be alleviated by use of a feedback control mechanism that coordinates the emission of the sources. The authors present a dynamic resource management mechanism that both controls the losses at the congested node and attempts to optimize resource utilization. In fact it steers the entire system into a desirable operating regime. They study analytically the behavior of the system under such a control and show that it can be reduced with a few approximations to a well-known physical system. This allows to infer optimal values for the parameters of the command algorithm, and the authors show that these values have a natural physical meaning to the system View full abstract»

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  • Sensing the state of voice sources to improve multiplexer performance

    Page(s): 56 - 63 vol.1
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    The control of source-coded traffic at a multiplexer has been a topic of extensive research. Traditional approaches typically use feedback information on the buffer level in designing the control policy. While important, buffer levels capture only part of the information about the overall system state. By setting up this problem as a Markov decision process, the authors show that using information on the state (activity) of the sources, in addition to the buffer level, can result in significant improvements over traditional approaches. They demonstrate this for a multiplexer fed by μ-law encoded voice sources. Some of the scenarios studied exhibit a reduction in distortion exceeding 35%. In general, the improvement is heavily dependent on the correlation statistics of the sources. Emulations validate the analysis. The form and characteristics of the optimal control policies are also discussed View full abstract»

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  • Least cost routing in multi-service networks. II

    Page(s): 289 - 296 vol.1
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    In Part I, we proposed a distributed, state dependent, dynamic routing method, called least cost routing in multi-service networks (LCRM), for multirate circuit-switched broadband ISDN networks, which support a variety of traffic classes with different characteristics. This method represents the one-step policy improvement on a chosen base policy. As a base policy π0, we use the policy which allows direct link routing only. The policy π0 also requires that each call class has a portion of link bandwidth dedicated to it. The task is to find an efficient computational way to obtain the corresponding relative cost values, which represent costs of routing a call over one link. We consider the one-link model with two types of traffic. Our main result is that the system of linear equations associated with the two-dimensional Markov chain can be decomposed into several systems of linear equations, each one associated with the one-dimensional Markov chain View full abstract»

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  • A source-based algorithm for delay-constrained minimum-cost multicasting

    Page(s): 377 - 385 vol.1
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    A new heuristic algorithm is presented for constructing minimum-cost multicast trees with delay constraints. The new algorithm can set variable delay bounds on destinations and handles two variants of the network cost optimization goal: one minimizing the total cost (total bandwidth utilization) of the tree, and another minimizing the maximal link cost (the most congested link). Instead of the single-pass tree construction approach used in most previous heuristics, the new algorithm is based on a feasible search optimization method which starts with the minimum-delay tree and monotonically decreases the cost by iterative improvement of the delay-bounded tree. The optimality of the costs of the delay-bounded trees obtained with the new algorithm is analyzed by simulation. Depending on how tight the delay bounds are, the costs of the multicast trees obtained with the new algorithm are shown to be very close to the costs of the trees obtained by the Kou, Markowsky and Berman's algorithm (1981) View full abstract»

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  • Dynamic maintenance of the virtual path layout

    Page(s): 330 - 337 vol.1
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    Discusses methods for adjusting the layout of virtual paths in an ATM network, to the dynamics of changes in the usage of the network by its end-users. The authors first present a centralized algorithm for finding a better layout for the current traffic pattern, and for applying the change in the network, and discuss its drawbacks. They then present a distributed algorithm that emulates the centralized algorithm with a much lower overhead, and enhanced durability to faults. They prove that both algorithms produce identical layouts, thus showing the superiority of the latter algorithm. Both algorithms base the changes in the network on a new rerouting protocol, which does not cause any losses in data, nor changes in the FIFO order of cells View full abstract»

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  • Fast simulation of a voice-data multiplexer

    Page(s): 361 - 368 vol.1
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    This paper considers the problem of estimating, via simulation, extremely low packet loss rates in a voice-data multiplexer. The multiplexer gives priority to voice packets, unless the data queue length exceeds a threshold. To efficiently simulate such low loss rates requires the proper use of importance sampling. In this paper we describe an importance sampling technique that is guaranteed to provide an exponential decrease in variance over standard simulation. This importance sampling technique has two phases, with a different importance sampling strategy in each phase. Experimental results are presented that demonstrate the effectiveness of this approach View full abstract»

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  • Topological design of local area networks using genetic algorithms

    Page(s): 64 - 71 vol.1
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    Continually growing number of users have to exchange increasing amounts of information. Local area networks (LANs) are commonly used as the communication infrastructure that meets the demands of the users in the local environment. These networks typically consist of several LAN segments connected together via bridges. The authors describe an algorithm for designing LANs with the objective of minimizing the average network delay. The topology design includes issues such as determination of the number of segments in the network, allocating the users to the different segments and determining the interconnections and routing among the segments. The determination of the optimal LAN topology is a complicated combinatorial optimisation problem. Therefore, a heuristic algorithm which is based on genetic ideas is used. Numerical examples are provided and the quality of the designs obtained by using the algorithm is compared with lower bounds on the average network delay that are developed View full abstract»

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  • Topological design of loss-free switch-based LANs

    Page(s): 88 - 96 vol.1
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    The paper presents a new design methodology and tools to construct a switch-based LAN with (i) scalable throughput, (ii) no loss due to congestion, and (iii) two routing modes: FIFO or non-FIFO. More specifically, given a bounded degree (number of switch ports) at each node, the design is based on the construction of multiple virtual rings under the following constraints: (i) the virtual rings are pairwise edge-disjoint, and (ii) there is at least one virtual ring between any pair of nodes. The target topology is obtained from the edge union of the multiple virtual rings. The objectives of the above two constraints are (i) to ensure no loss due to congestion inside the network of bursty traffic sources, and (ii) to ensure convergence of packets/cells to their destinations. The virtual rings are constructed by a new methodology that employs combinatorial block designs together with a new algorithm for realizing any size networks. It is shown that the bound on the maximum route length, under the two constraints, is O(√N) for an N-node network View full abstract»

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  • Radio link admission algorithms for wireless networks with power control and active link quality protection

    Page(s): 97 - 104 vol.1
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    Presents a distributed power control scheme, which maintains the signal/interference ratios (SIRs) of operational (active) links above their required thresholds at all times (link quality protection), while new users are being admitted; furthermore, when new users cannot be successfully admitted, existing ones do not suffer fluctuations of their SIRs below their required thresholds values. The authors also present two admission/rejection control algorithms, which exercise voluntary drop-out of links inadmissible to the network so as to reduce interference and possibly facilitate the admission of other links View full abstract»

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  • The distribution of delays of dispersed messages in an M/M/1 queue

    Page(s): 338 - 344 vol.1
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    We analyze the distribution of the delay of messages in an infinite capacity M/M/1 queue. A message is composed of n packets, and the arrival of the packets to the queue is Poisson. Our calculations are based on recursive schemes. We obtain explicit expressions for the Laplace-Stieltjes transform (LST) of the delays, which enables to obtain exact expressions for the moments of the delay in a complexity smaller than the one obtained by using recursive schemes. We repeat the above calculations for the case that messages are dispersed, i.e. packets from several sources arrive to an M/M/1 queue and are served according to the FIFO discipline. Hence, several packets of other messages may arrive between consecutive packets of a given message View full abstract»

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  • Computable exponential bounds for intree networks with routing

    Page(s): 197 - 204 vol.1
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    In this paper, we refine the calculus proposed previously by Chang et al. (1994). The new calculus, including network operations for multiplexing, input-output relation, and routing, allows us to compute tighter exponential bounds for the tail distributions of queue lengths in intree networks with routing. In particular, if external arrival processes and routing processes are either Markov arrival processes or autoregressive processes, the stationary queue length at a local node is stochastically bounded above by the sum of a constant and an Erlang random variable. The decay rate of the Erlang random variable is not greater than (in some cases equal to) the decay rate of the tail distribution of the stationary queue length. The number of stages of the Erlang random variable is the number of external arrival processes and routing processes contributing to its queue length. For the single queue case, both the lower and upper-bounds are derived View full abstract»

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  • Mobile radio slotted ALOHA with capture and diversity

    Page(s): 121 - 128 vol.1
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    The slotted ALOHA protocol in a mobile radio environment, in the presence of Ricean fading, twofold antenna diversity and multiple reception capability, is considered. The capture probabilities and the average throughput are computed, and the issue of stability is addressed. It is shown that diversity can improve the system performance, although only to a certain extent. Some extensions are also considered: in particular the use of a higher degree of diversity is investigated View full abstract»

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  • Virtual path bandwidth allocation in multi-user networks

    Page(s): 312 - 320 vol.1
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    Considers a multi-user network that is shared by noncooperative users. Each user sets up virtual paths that optimize its own, selfish, performance measure. This measure accounts for both the guaranteed call level quality of service, as well as for the cost incurred for reserving the resource. The interaction between the user strategies is formalized as a game. The authors show that this game has a unique Nash equilibrium, and that it possesses a certain fairness property. They investigate the dynamics of this game, and prove convergence to the Nash equilibrium of both a Gauss-Seidel scheme and a Jacobi scheme. They extend their study to various general network topologies View full abstract»

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  • Receiver-oriented adaptive buffer allocation in credit-based flow control for ATM networks

    Page(s): 239 - 252 vol.1
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    In credit-based flow control for ATM networks, a buffer is first allocated to each VC (virtual circuit) and then credit control is applied to the VC for avoiding possible buffer overflow. Receiver-oriented, adaptive buffer allocation allows a receiver to allocate its buffer dynamically, to VCs from multiple upstream nodes based on their bandwidth usage. The paper describes, in detail, such an adaptive algorithm capable of supporting a wide range of link speeds and propagation delays, and also packing multiple allocation and credit records in a single message. Analysis and simulation results show that even under highly bursty traffic, the adaptive scheme guarantees no cell loss due to congestion, and achieves excellent performance in utilization, fairness, ramp-up and packing, while requiring only relatively small node memory and bandwidth overhead. The required memory need only be 4*RTT+2*N, where RTT is the link round-trip time in cell cycles and N is the number of VCs View full abstract»

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  • Implementation of self-healing function in ATM networks based on virtual path concept

    Page(s): 303 - 311 vol.1
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    This paper proposes an implementation scheme for the self-healing function in ATM networks and assesses its performance. First, our proposed ATM self-healing scheme is described. This scheme realizes more rapid restoration of failed virtual paths than other self-healing algorithms, supports the node failure case, and minimizes the spare resources required. Next, an implementation scheme is proposed. We propose that the self-healing function be implemented as a software process, and that OAM cells are utilized for fast message transmission. Next, results of a prototype system that we implemented on an ATM cross-connect system are discussed. The fundamental characteristics of restoration performance are measured using an experimental network. Based on these results, an NE processing system analysis and computer simulation for estimating the characteristics as applied to a real-scale network are discussed. Finally, a management scheme for self-healing is proposed based on the TMN concept View full abstract»

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  • Multiplexing spacer outputs on cell emissions

    Page(s): 49 - 55 vol.1
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    In ATM networks, one effective way to provide service guarantees is to shape individual traffic streams at various points in the network. In the paper, the authors present a method for multiplexing a large number of single-stream spacer outputs on cell emissions rather than on cell arrivals. The method not only approximates first come first served (FCFS) multiplexing of such outputs but also better suits bursty arrivals. A number of performance related issues of the proposed method are identified and examined View full abstract»

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  • An optimal establishment of virtual path connections for ATM networks

    Page(s): 72 - 79 vol.1
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    A number of optimization models for the establishment of virtual path connections (VPCs) with reserved capacity have been proposed in the literature. All of them, however, failed to reflect the trade-off between increased capacity costs and reduced control costs explicitly in their formulations. the present authors develop a mathematical formulation for an optimal strategy for the reservation of capacity on VPCs, considering the trade-off between increased capacity costs and reduced control costs. In this formulation, they also consider the reservation of buffers on VPCs. Algorithms and numerical results are presented View full abstract»

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