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Networking, IEEE/ACM Transactions on

Issue 6 • Date Dec. 2000

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Displaying Results 1 - 12 of 12
  • Author index

    Page(s): 1 - 3
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    Freely Available from IEEE
  • Subject index

    Page(s): 3 - 9
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    Freely Available from IEEE
  • Optimal smoothing for guaranteed service

    Page(s): 689 - 696
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    We consider the transmission of variable bit rate (VBR) video over a network offering a guaranteed service such as ATM VBR or the guaranteed service of the IETF. The guaranteed service requires that the flow accepted by the network has to be conforming with a traffic envelope σ; in return, it receives a service guarantee expressed by a network service curve β. Functions α and β are derived from the parameters used for setting up the reservation, for example, from the T-SPEC and R-SPEC fields used with the resource reservation protocol (RSVP). In order to satisfy the traffic envelope constraint, the output of the encoder is fed to a smoother, possibly with some look-ahead. The resulting stream is transported by the network; at the destination, the decoder waits for an initial playback delay and reads the stream from the receive buffer. We consider the problem of whether there exists one optimal strategy at the smoother which minimizes the playback delay and the receive buffer size, given the traffic envelope α and the service curve β. We show that there does exist such an optimal smoothing, and give an explicit representation for it. We also obtain a simple expression for the smallest playback delay and playback buffer size which can be achieved over all possible smoothing and playback strategies. We show that the computation of optimal smoothing and minimum playback delay do not depend on the past. We show that separate delay equalization is optimal in the constant bit rate (CBR) case, but not otherwise. We also apply the theory to the analysis of which T-SPEC should be requested by a source-destination pair, given some playback delay and buffer constraint, and given the path characteristics advertised in RSVP PATH messages View full abstract»

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  • A study of deadlock models for a multiservice medium access protocol employing a slotted Aloha signalling channel

    Page(s): 800 - 811
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    Medium access protocols for HFC and wireless ATM networks often use a collision based capacity request signalling channel which may rely on the slotted Aloha multiaccess principle. This paper studies the performance of a p-persistence slotted Aloha contention resolution algorithm (CRA), subject to extreme interstation correlation, by means of a discrete-time Markov chain analysis. We examine in detail the conditions leading to a deadlock-a situation where the time to collision resolution becomes unacceptably high and the system is practically unstable. We analyze two disaster scenario deadlock models, and study the effect of channel error probability, signalling traffic load, and the contention resolution algorithm used. We show that the key factor of the CRA is the collision rate and not channel errors. We propose and test three signalling channel capacity allocation schemes. We identify the best-performing of these three schemes as the cyclic contention mini-slot (CMS) sharing employing multiple CMSs per data slot. Finally, we demonstrate the need for implementation of an added scheme, which dynamically adjusts the p-persistence parameter View full abstract»

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  • Performance modeling of multihop network subject to uniform and nonuniform geometric traffic

    Page(s): 763 - 774
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    Performance modeling under nonuniform traffic is a useful tool to validate simulation accuracy and lend insights to realistic implementation of multihop networks. We present memoryless and independence assumptions based performance models capable of tracking nonuniform traffic for an arbitrary multihop network with the deflection and store-and-forward routing strategies. We also include a description of the efficient numerical algorithms, and provide comparisons to simulation. Our models are a generalization of Greenberg-Goodman (1986, 1992), Greenberg-Hajek (1992), Hajek-Krishna (1990), and Brassil-Cruz (1991, 1993) models View full abstract»

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  • Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit

    Page(s): 785 - 799
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    In wireless LANs (WLANs), the medium access control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel. In this paper we focus on the efficiency of the IEEE 802.11 standard for WLANs. Specifically, we analytically derive the average size of the contention window that maximizes the throughput, hereafter theoretical throughput limit, and we show that: 1) depending on the network configuration, the standard can operate very far from the theoretical throughput limit; and 2) an appropriate tuning of the backoff algorithm can drive the IEEE 802.11 protocol close to the theoretical throughput limit. Hence we propose a distributed algorithm that enables each station to tune its backoff algorithm at run-time. The performances of the IEEE 802.11 protocol, enhanced with our algorithm, are extensively investigated by simulation. Specifically, we investigate the sensitiveness of our algorithm to some network configuration parameters (number of active stations, presence of hidden terminals). Our results indicate that the capacity of the enhanced protocol is very close to the theoretical upper bound in all the configurations analyzed View full abstract»

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  • On the cost of virtual private networks

    Page(s): 775 - 784
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    A virtual private network (VPN) is a private data network that uses a nonprivate data network to carry traffic between remote sites. An “Intranet VPN” establishes network layer connectivity between remote Intranet sites by creating an IP overlay network over the nonprivate network, using various tunneling mechanisms. There are two approaches for establishing such tunnels: a “CPE-based approach” and a “network-based approach.” In the first approach, tunnels are established only between the CPE devices, whereas in the second approach tunnels are also established between the routers of the core nonprivate network. In this paper we address the problem of determining a CPE-based and a network-based layout of VPN tunnels while taking into account two factors: the cost of the links over which the VPN tunnels are established and the cost of the core routers that serve as end points for the VPN. We define related graph algorithm problems, analyze their complexity, and present heuristics for solving these problems efficiently View full abstract»

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  • A predictive self-tuning fuzzy-logic feedback rate controller

    Page(s): 697 - 709
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    This paper addresses the design and analysis of an end-to-end rate-based feedback flow control algorithm motivated by the available bit rate (ABR) service in wide-area asynchronous transfer mode (ATM) networks. Recognizing that the explicit feedback rate at time t will not affect the ABR buffer until time t+D for some D⩾0, our approach is to first predict the ABR buffer status at time t+D, then base fuzzy-logic rate control decisions on these predicted values, and finally tune the controller parameters using gradient descent methods. Simulations show that this predictive self-tuning fuzzy-logic (PSTF) control scheme is efficient, stable, and outperforms other proposed ABR rate controllers in a variety of network environments. With delays corresponding to a US coast-to-coast connection, the PSTF controller can maintain high link utilization, avoid buffer overflows, and provide fair allocation of resources View full abstract»

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  • Source-adaptive multilayered multicast algorithms for real-time video distribution

    Page(s): 720 - 733
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    Layered transmission of data is often recommended as a solution to the problem of varying bandwidth constraints in multicast video applications. Multilayered encoding, however, is not sufficient to provide high video quality and high network utilization, since bandwidth constraints frequently change over time. Adaptive techniques capable of adjusting the rates of video layers are required to maximize video quality and network utilization. We define a class of algorithms known as source-adaptive multilayered multicast (SAMM) algorithms. In SAMM algorithms, the source uses congestion feedback to adjust the number of generated layers and the bit rate of each layer. We contrast two specific SAMM algorithms: an end-to-end algorithm, in which only end systems monitor available bandwidth and report the amount of available bandwidth to the source, and a network-based algorithm, in which intermediate nodes also monitor and report available bandwidth. Using simulations that incorporate multilayered video codecs, we demonstrate that SAMM algorithms can exhibit better scalability and responsiveness to congestion than algorithms that are not source-adaptive. We also study the performance trade-offs between end-to-end and network-based SAMM algorithms View full abstract»

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  • A gamma-based framework for modeling variable-rate MPEG video sources: the GOP GBAR model

    Page(s): 710 - 719
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    A flexible model called the group-of-pictures gamma-beta auto-regression (GOP GBAR) model based on gamma-distributed variables is proposed for variable-rate MPEG video sources. This model is an extension of Heyman's (see IEEE/ACM Trans. Networking, vol.5, p.554-60, 1997) GBAR model for video teleconferencing. The GOP GBAR model explicitly accounts for MPEG GOP cyclicity and has convenient analytical properties with easily estimated parameters. Possible extensions of the GOP GBAR model are proposed to capture special features of MPEG video View full abstract»

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  • A path decomposition approach for computing blocking probabilities in wavelength-routing networks

    Page(s): 747 - 762
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    We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wavelength converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed in isolation, and the individual results are appropriately combined to obtain a solution for the overall network. To analyze individual subsystems, we first construct an exact Markov process that captures the behavior of a path in terms of wavelength use. We also obtain an approximate Markov process which has a closed-form solution that can be computed efficiently for short paths. We then develop an iterative algorithm to analyze approximately arbitrarily long paths. The path decomposition approach naturally captures the correlation of both link loads and link blocking events. Our algorithm represents a simple and computationally efficient solution to the difficult problem of computing call-blocking probabilities in wavelength-routing networks. We also demonstrate how our analytical techniques can be applied to gain insight into the problem of converter placement in wavelength-routing networks View full abstract»

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  • New dynamic algorithms for shortest path tree computation

    Page(s): 734 - 746
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    The open shortest path first (OSPF) and IS-IS routing protocols widely used in today's Internet compute a shortest path tree (SPT) from each router to other routers in a routing area. Many existing commercial routers recompute an SPT from scratch following changes in the link states of the network. Such recomputation of an entire SPT is inefficient and may consume a considerable amount of CPU time. Moreover, as there may coexist multiple SPTs in a network with a set of given link states, recomputation from scratch causes frequent unnecessary changes in the topology of an existing SPT and may lead to routing instability. We present new dynamic SPT algorithms that make use of the structure of the previously computed SPT. Besides efficiency, our algorithm design objective is to achieve routing stability by making minimum changes to the topology of an existing SPT (while maintaining shortest path property) when some link states in the network have changed. We establish an algorithmic framework that allows us to characterize a variety of dynamic SPT algorithms including dynamic versions of the well-known Dijkstra, Bellman-Ford, D'Esopo-Pape algorithms, and to establish proofs of correctness for these algorithms in a unified way. The theoretical asymptotic complexity of our new dynamic algorithms matches the best known results in the literature View full abstract»

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Aims & Scope

The IEEE/ACM Transactions on Networking’s high-level objective is to publish high-quality, original research results derived from theoretical or experimental exploration of the area of communication/computer networking.

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Meet Our Editors

Editor-in-Chief
R. Srikant
Dept. of Electrical & Computer Engineering
Univ. of Illinois at Urbana-Champaign