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Networking, IEEE/ACM Transactions on

Issue 4 • Date Aug 2001

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Displaying Results 1 - 12 of 12
  • Analysis of Web caching architectures: hierarchical and distributed caching

    Page(s): 404 - 418
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    Cache cooperation improves the performance of isolated caches, especially for caches with small cache populations. To make caches cooperate on a large scale and effectively increase the cache population, several caches are usually federated in caching architectures. We discuss and compare the performance of different caching architectures. In particular, we consider hierarchical and distributed caching. We derive analytical models to study important performance parameters of hierarchical and distributed caching, i.e., client's perceived latency, bandwidth usage, load in the caches, and disk space usage. Additionally, we consider a hybrid caching architecture that combines hierarchical caching with distributed caching at every level of a caching hierarchy. We evaluate the performance of a hybrid scheme and determine the optimal number of caches that should cooperate at each caching level to minimize client's retrieval latency View full abstract»

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  • An adaptive FEC scheme for data traffic in wireless ATM networks

    Page(s): 419 - 426
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB) |  | HTML iconHTML  

    A new adaptive forward-error-correction scheme (AFEC) is introduced at the link layer for TCP/IP data traffic in wireless ATM networks. The fading and interference in wireless links cause high and variable error rates, as well as bursty errors. The purpose of the AFEC scheme is to provide a dynamic error-control mechanism by using Reed-Solomon coding to protect the ATM cell payload, as well as the payload type indicator/cell loss priority fields in the ATM cell header. In order to enhance the error tolerance in cell framing and correct delivery, the AFEC scheme functions within a new concept called LANET framing and addressing protection mechanisms. The AFEC scheme has been validated using a simulation testbed of a low-speed wireless ATM network View full abstract»

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  • TCP performance over end-to-end rate control and stochastic available capacity

    Page(s): 377 - 391
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    Motivated by TCP over end-to-end ABR, we study the performance of adaptive window congestion control, when it operates over an explicit feedback rate-control mechanism, in a situation in which the bandwidth available to the elastic traffic is stochastically time varying. It is assumed that the sender and receiver of the adaptive window protocol are colocated with the rate-control endpoints. The objective of the study is to understand if the interaction of the rate-control loop and the window-control loop is beneficial for end-to-end throughput, and how the parameters of the problem (propagation delay, bottleneck buffers, and rate of variation of the available bottleneck bandwidth) affect the performance. The available bottleneck bandwidth is modeled as a two-state Markov chain. We develop an analysis that explicitly models the bottleneck buffers, the delayed explicit rate feedback, and TCP's adaptive window mechanism. The analysis, however, applies only when the variations in the available bandwidth occur over periods larger than the round-trip delay. For fast variations of the bottleneck bandwidth, we provide results from a simulation on a TCP testbed that uses Linux TCP code, and a simulation/emulation of the network model inside the Linux kernel. We find that, over end-to-end ABR, the performance of TCP improves significantly if the network bottleneck bandwidth variations are slow as compared to the round-trip propagation delay. Further, we find that TCP over ABR is relatively insensitive to bottleneck buffer size. These results are for a short-term average link capacity feedback at the ABR level (INSTCAP). We use the testbed to study EFFCAP feedback, which is motivated by the notion of the effective capacity of the bottleneck link. We find that EFFCAP feedback is adaptive to the rate of bandwidth variations at the bottleneck link, and thus yields good performance (as compared to INSTCAP) over a wide range of the rate of bottleneck bandwidth variation. Finally, we study if TCP over ABR, with EFFCAP feedback, provides throughput fairness even if the connections have different round-trip propagation delays View full abstract»

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  • A novel scheme using the information of departure processes for delay guarantees of distributed VBR traffic

    Page(s): 452 - 463
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    In this paper, we consider the problem of providing delay guarantees in a distributed environment, e.g., a wireless network or a cable network. In a distributed environment, the information of the arrival process is, in general, not available to the network. Due to the lack of such information, traffic regulators and scheduling policies discussed in the literature cannot be directly applied. To cope with the problem, we propose a distributed traffic regulator (DTR) that uses the information of the departure process. Based on such DTRs, we propose the distributed earliest deadline first (DEDF) scheduling policy. For the DEDF scheme, we derive an admission-control criterion and show that the maximum delay can be guaranteed if the criterion is satisfied View full abstract»

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  • Bandwidth-allocation policies for unicast and multicast flows

    Page(s): 464 - 478
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    Using multicast delivery to multiple receivers reduces the aggregate bandwidth required from the network compared to using unicast delivery to each receiver. However, multicast is not yet widely deployed in the Internet. One reason is the lack of incentive to use multicast delivery. To encourage the use of multicast delivery, we define a new bandwidth-allocation policy, called LogRD, taking into account the number of downstream receivers. This policy gives more bandwidth to a multicast flow as compared to a unicast flow that shares the same bottleneck, without starving the unicast flows, however. The LogRD policy also provides an answer to the question on how to treat a multicast flow compared to a unicast flow sharing the same bottleneck. We investigate three bandwidth-allocation policies for multicast flows and evaluate their impact on both receiver satisfaction and fairness using a simple analytical study and a comprehensive set of simulations. The policy that allocates the available bandwidth as a logarithmic function of the number of receivers downstream of the bottleneck achieves the best tradeoff between receiver satisfaction and fairness View full abstract»

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  • The performance of query control schemes for the zone routing protocol

    Page(s): 427 - 438
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB) |  | HTML iconHTML  

    We study the performance of route query control mechanisms for the zone routing protocol (ZRP) for ad hoc networks. The ZRP proactively maintains routing information for a local neighborhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. This hybrid routing approach can be more efficient than traditional routing schemes. However, without proper query control techniques, the ZRP cannot provide the expected reduction in the control traffic. Our proposed query control schemes exploit the structure of the routing zone to provide enhanced detection and prevention of overlapping queries. These techniques can be applied to single- or multiple-channel ad hoc networks to improve both the delay and control traffic performance of ZRP. Our query control mechanisms allow ZRP to provide routes to all accessible network nodes, with less control traffic than purely proactive link state or purely reactive route discovery, and with less delay than conventional flood searching View full abstract»

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  • Difficulties in simulating the Internet

    Page(s): 392 - 403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    Simulating how the global Internet behaves is an immensely challenging undertaking because of the network's great heterogeneity and rapid change. The heterogeneity ranges from the individual links that carry the network's traffic, to the protocols that interoperate over the links, the “mix” of different applications used at a site, and the levels of congestion seen on different links. We discuss two key strategies for developing meaningful simulations in the face of these difficulties: searching for invariants and judiciously exploring the simulation parameter space. We finish with a look at a collaborative effort within the research community to develop a common network simulator View full abstract»

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  • Optimal structured feedback policies for ABR flow control using two-timescale SPSA

    Page(s): 479 - 491
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    Optimal structured feedback control policies for rate-based flow control of available bit rate service in asynchronous transfer mode networks are obtained in the presence of information and propagation delays, using a numerically efficient two-timescale simultaneous perturbation stochastic approximation (SPSA) algorithm. Models comprising both a single bottleneck node and a network with multiple bottleneck nodes are considered. A convergence analysis of the algorithm is presented. Numerical experiments demonstrate fast convergence even in the presence of significant delays. We also illustrate performance comparisons with the well-known explicit rate indication for congestion avoidance (ERICA) algorithm and describe another algorithm (based on ERICA) that does not require estimating available bandwidth (as in ERICA) View full abstract»

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  • Equivalent permutation capabilities between time-division optical Omega networks and non-optical extra-stage Omega networks

    Page(s): 518 - 524
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB) |  | HTML iconHTML  

    Because signals carried by two waveguides entering a common switch element would generate crosstalk, a regular N×N multistage interconnection network (MIN) cannot be directly used as an optical switch between N inputs and N outputs in an optical network. A simple solution is to use a 2N×2N cube-type MIN to provide the N×N connections, which needs a much larger hardware cost. A previous research proposed another solution, called the time-domain approach, that divides the N optical inputs into several groups such that crosstalk-free connections can be provided by an N×N regular MIN in several time slots, one for each group. Researchers studied this approach on Omega networks and defined the class set θ to be the set of N-permutations realizable in two time slots on an Omega network. They proved that the size of θ is larger than the size of class Ω, where Ω consists of all N-permutations admissible to a regular N×N (nonoptical) Omega network. This paper first presents an optimal O(NlogN) time algorithm for identifying whether a given permutation belongs to class θ or not. Using this algorithm, this paper then proves an interesting result that the class θ is identical to the class Ω+1 which represents the set of N-permutations admissible to a nonoptical N×N one-extra stage Omega network View full abstract»

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  • An analysis of oblivious and adaptive routing in optical networks with wavelength translation

    Page(s): 503 - 517
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    We present an analysis for both oblivious and adaptive routing in regular, all-optical networks with wavelength translation. Our approach is simple, computationally inexpensive, accurate for both low and high network loads, and the first to analyze adaptive routing with wavelength translation in wavelength division multiplexed (WDM) networks while also providing a simpler formulation of oblivious routing with wavelength translation. Unlike some previous analyses which use the link independence blocking assumption and the call dropping (loss) model (where blocked calls are cleared), we account for the dependence between the acquisition of wavelengths on successive links of a session's path and use a lossless model (where blocked calls are retried at a later time). We show that the throughput per wavelength increases superlinearly (as expected) as we increase the number of wavelengths per link, due both to additional capacity and more efficient use of this capacity; however, the extent of this superlinear increase in throughput saturates rather quickly to a linear increase. We also examine the effect that adaptive routing can have on performance. The analytical methodology that we develop can be applied to any vertex and edge symmetric topology, and with modifications, to any vertex symmetric (but not necessarily edge symmetric) topology. We find that, for the topologies we examine, providing at most one alternate link at every hop gives a per wavelength throughput that is close to that achieved by oblivious routing with twice the number of wavelengths per link. This suggests some interesting possibilities for network provisioning in an all-optical network. We verify the accuracy of our analysis for both oblivious and adaptive routing via simulations for the torus and hypercube networks View full abstract»

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  • An efficient polling MAC for wireless LANs

    Page(s): 439 - 451
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Polling schemes are an important class of medium access control (MAC) protocols for wireless local area networks (WLANs). A major drawback of these schemes is their inefficiency when only a small number of mobile stations have packets to transmit. This inefficiency is due to the polling of mobile stations with no packets to transmit, which delays the transmissions of mobile stations with packets. In this paper, we suggest a new polling MAC which exploits the capture phenomena and enables simultaneous polling and transmissions of information packets. Mathematical analysis and simulation results show that the new MAC overcomes the above inefficiency considerably, and thus it is more efficient in the sense that it enables higher throughput and a lower access delay. For example, we show scenarios in which the average access delay is reduced by about 30% and the throughput increases by 66%-75% View full abstract»

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  • Jitter control in QoS networks

    Page(s): 492 - 502
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    We study jitter control in networks with guaranteed quality of service (QoS) from the competitive analysis point of view: we propose on-line algorithms that control jitter and compare their performance to the best possible (by an off-line algorithm) for any given arrival sequence. For delay jitter, where the goal is to minimize the difference between delay times of different packets, we show that a simple on-line algorithm using a buffer of B slots guarantees the same delay jitter as the best off-line algorithm using buffer space B/2. We prove that the guarantees made by our on-line algorithm hold, even for simple distributed implementations, where the total buffer space is distributed along the path of the connection, provided that the input stream satisfies a certain simple property. For rate jitter, where the goal is to minimize the difference between inter-arrival times, we develop an on-line algorithm using a buffer of size 2B+h for any h⩾1, and compare its jitter to the jitter of an optimal off-line algorithm using buffer size B. We prove that our algorithm guarantees that the difference is bounded by a term proportional to B/h 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