R. Cohen

Technion - Israel Institute of Technology, H̱efa, Haifa, Israel

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Publications (6)1.81 Total impact

  • Source
    Reuven Cohen · Liran Katzir · Danny Raz
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    ABSTRACT: Cache pre-filling is emerging as a new concept for increasing the availability of popular Web items in cache servers. According to this concept, Web items are sent by a "push-server" to the proxy cache servers, usually through a broadcast-based or a multicast-based distribution mechanism. One of the most difficult challenges is to design the scheduling algorithm of the push-server. This algorithm needs to determine the "broadcast scheduling map", namely which Web items to broadcast and when. In this paper we study the approach where every constant period of time each proxy cache analyzes the requests it has received in the past and determines which Web item it prefers to receive by broadcast and when. We formalize a related problem, called the "cache pre-filing push" (CPFP) problem, analyze its computational complexity, and describe efficient algorithms to solve it.
    Preview · Conference Paper · Feb 2002
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    E. Bortnikov · R. Cohen
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    ABSTRACT: The paper addresses the problem of designing efficient scheduling policies for the transmission of control messages by hierarchical network protocols. Such protocols encounter a tradeoff between the desire to forward a control message across the tree as soon, as it is received, and the desire to reduce control traffic. Scheduling problems that arise in this context are defined and discussed. The paper mainly concentrates on minimizing the average extra delay encountered by the control messages under an upper bound on the number of outgoing messages a node can send during a fixed period of time. A polynomial-time algorithm is presented for the off-line version of the problem, and then several efficient on-line heuristics are presented and compared
    Preview · Conference Paper · Apr 2001
  • Source
    R. Cohen · Y. Hamo
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    ABSTRACT: TCP suffers from low performance over asynchronous transfer mode (ATM) networks. This is mainly because during phases of congestion, ATM drops cells without taking into account the effect this has on the upper layer protocols. Two main algorithms, called PPD and EPD, were proposed in the past for improving TCP performance. However they address one aspect of the problem, that has only small effect on the final performance. In this paper we propose an enhanced method for packet discard, called balanced packet discard (BPD), that improves TCP performance dramatically on congested networks and guarantees fairness among multiple connections. We show that BPD increases TCP throughput by more than 25% compared to EPD/PPD
    Preview · Conference Paper · Apr 2000
  • Source
    R. Cohen · E. Felstaine · R. Emek
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    ABSTRACT: We propose a framework for the creation and maintenance of multicast trees in hierarchical ATM networks. This framework aims at coping with an inherent difficulty of topology aggregation in such networks. The main idea of the proposed framework is to distribute the tree topology information among a set of hierarchical multicast group servers (MGS) nominated for each multicast tree, while keeping regions that do not have a member in the multicast group unaware of the tree. The framework can be employed with every multicast routing algorithm designed for non-hierarchical networks
    Full-text · Conference Paper · Apr 2000
  • Source
    E. Felstaine · R. Cohen
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    ABSTRACT: ATM private network-to-network interface (PNNI) is a hierarchical and dynamic link-state routing protocol, designed to scale to the largest possible ATM networks, encompassing thousands of nodes. This paper investigates the route computation load imposed by the PNNI routing scheme, and shows that this load is unevenly distributed among the network nodes. More specifically, the routing computation load associated with the setup of a single virtual path grows exponentially with the hierarchy level. As a result, some of the network nodes-mainly those that function as border nodes of high levels-may be overloaded with route computation, while other nodes are rarely involved in this process. This paper also proposes a possible scheme for spreading the route computation burden more evenly. According to this scheme, heavily loaded nodes transfer route computation tasks to lightly loaded nodes
    Full-text · Article · Jan 2000 · IEEE/ACM Transactions on Networking
  • Source
    E. Felstaine · R. Cohen · O. Hader
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    ABSTRACT: When an ATM node discovers that it cannot continue the setup of a virtual channel under the requested QoS, it initiates a back-tracking procedure called “crankback”. We propose a novel scheme, referred to as crankback prediction, that decreases the crankback overhead. Under the proposed scheme, nodes check during the connection admission control procedure whether the establishment of a virtual channel has a good chance to be admitted over the entire designated route. If this is not the ease, crankback is initiated even before a certain QoS parameter is exceeded
    Full-text · Conference Paper · Apr 1999