Sofia, Rute

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  • Publication
    Distributed Path Computation without Transient Loops: An Intermediate Variables Approach
    (2007-06-17) Ray, Saikat; Guérin, Roch A; Sofia, Rute
    Paths with loops, even transient ones, pose significant stability problems in networks. As a result, much effort has been devoted over the past thirty years to designing distributed algorithms capable of avoiding loops. We present a new algorithm, Distributed path computation with Intermediate Variables (DIV), that guarantees that no loops, transient or steady-state, can ever form. DIV’s novelty is in that it is not restricted to shortest paths, can easily handle arbitrary sequences of changes and updates, and provably outperforms earlier approaches in several key metrics. In addition, when used with distance-vector style path computation algorithms, DIV also prevents counting-to-infinity; hence further improving convergence. The paper introduces DIV and its key properties. Simulation quantifying its performance gains are also presented.
  • Publication
    A Distributed Hash Table based Address Resolution Scheme for Large-scale Ethernet Networks
    (2007-06-24) Ray, Saikat; Guérin, Roch A; Sofia, Rute
    Ethernet's plug-&-play feature is built on its use of flat (location independent) addresses and use of broadcasts to resolve unknown MAC addresses. While plug-&-play is one of Ethernet's most attractive features, it also affects its scalability. As the number of active MAC addresses in the network grows beyond the capacity of forwarding caches in bridges, the odds of "cache-misses," each triggering a broadcast, grow as well. The resulting increase in broadcast bandwidth consumption affects scalability. To address this problem, we propose a simple address resolution scheme based on an adaptation of distributed hash tables where a single query suffices in the steady state. The new scheme is implemented on advanced bridges maintaining backward compatibility with legacy bridges and eliminating reliance on broadcasts for address discovery. Comparisons with a legacy, broadcast-based scheme are carried out along several metrics that demonstrate the new scheme's robustness and ability to improve scalability.