Analysis of a class of distributed queues with application

Recently we have developed a class of media access control algorithms for different types of Local Area Networks. A common feature of these LAN algorithms is that they represent various strategies by which the processors in the LAN can simulate the availability of a centralized packet transport facility, but whose service incorporates a particular type of change over time known as 'moving sever' overhead. First we describe the operation of moving server systems in general, for both First-Come - First-Served and Head-of-the-Line orders of service, together with an approach for their delay analysis in which we transform the moving server queueing system into a conventional queueing system having proportional waiting times. Then we describe how the various LAN algorithms may be obtained from the ideal moving server system, and how a significant component of their performance characteristics is determined by the performance characteristics of that ideal system. Finally, we evaluate the compatibility of such LAN algorithms with separable queueing network models of distributed systems by computing the interdeparture time distribution for M/M/1 in the presence of moving server overhead. Although it is not exponential, except in the limits of low server utilization or low overhead, the interdeparture time distribution is a weighted sum of exponential terms with a coefficient of variation not much smaller than unity. Thus, we conjecture that a service centre with moving server overhead could be used to represent one of these LAN algorithms in a product form queueing network model of a distributed system without introducing significant approximation errors

A New Binary Logarithmic Arbitration Method for Ethernet

Recently, Ethernet celebrated its twentieth anniversary. Over those years, the processing speed of the attached hosts has increased by several orders of magnitude, to the point where the relative bandwidth of a 10 Mbps Ethernet has fallen from more than adequate to support large enterprise networks (whose utilizations were typically only a few percent, anyway), to marginally fast enough to support a single high performance desktop workstation. At the same time, the Ethernet standard has also evolved to incorporate new technology at the physical layer, including new media, new signalling methods, and support for higher data rates. However, the MAC layer protocols have remained essentially unchanged from the early days of undemanding applications running on large numbers of slow hosts. In this paper, we argue that it is time to review the MAC layer and incorporate advances made in the protocol performance field over the last twenty years. First, we describe several little-known facts abo..

On the cutoff point for pairwise enabling in multiple access systems

In [1], we showed that the minimum probability p^0 for which pairwise enabling is an optimal group testing algorithm under an unbounded Bernoulli arrival sequence model satisfies 0.43

Analysis of a class of distributed queues with application

Recently we have developed a class of media access control algorithms for different types of Local Area Networks. A common feature of these LAN algorithms is that they represent various strategies by which the processors in the LAN can simulate the availability of a centralized packet transport facility, but whose service incorporates a particular type of change over time known as 'moving sever' overhead. First we describe the operation of moving server systems in general, for both First-Come - First-Served and Head-of-the-Line orders of service, together with an approach for their delay analysis in which we transform the moving server queueing system into a conventional queueing system having proportional waiting times. Then we describe how the various LAN algorithms may be obtained from the ideal moving server system, and how a significant component of their performance characteristics is determined by the performance characteristics of that ideal system. Finally, we evaluate the compatibility of such LAN algorithms with separable queueing network models of distributed systems by computing the interdeparture time distribution for M/M/1 in the presence of moving server overhead. Although it is not exponential, except in the limits of low server utilization or low overhead, the interdeparture time distribution is a weighted sum of exponential terms with a coefficient of variation not much smaller than unity. Thus, we conjecture that a service centre with moving server overhead could be used to represent one of these LAN algorithms in a product form queueing network model of a distributed system without introducing significant approximation errors

Localization with witnesses

Localization protocols enable an entity (called the verifier) to determine the physical location of another entity (called the prover), even if the prover maliciously advertises a false location or tries to corrupt the verifier’s time measurements by timeshifting its responses. Unfortunately, the correctness of such protocols is critically dependent on the verifier’s ability to make high-resolution time measurements and on the prover’s ability and trustworthiness to send its response by the mandated time. To address these problems, we propose the idea of incorporating passive witnesses into the localization protocol. All witnesses monitor the same bilateral packet exchange between the prover and lead verifier and later report their respective inter-packet time measurements to the lead verifier for further processing. We show how the extra information provided by the witnesses can eliminate the threat of response-time shifting by a malicious prover. We also pose the question, how can we combine multiple localization observations to a single localization estimate? While analyzing that, we observe that the localization estimate is sensitive to the relative position of the prover among the verifiers

Optimal Distributed Algorithm for Minimum Spanning Trees Revisited

In an earlier paper, Awerbuch presented an innovative distributed algorithm for solving minimum spanning tree (MST) problems that achieved optimal time and message complexity through the introduction of several advanced features. In this paper, we show that there are some cases where his algorithm can create cycles or fail to achieve optimal time complexity. We then show how to modify the algorithm to avoid these problems, and demonstrate both the correctness and optimality of the revised algorithm. 1 Introduction Given an undirected graph G with N nodes and E edges, with weights assigned to each edge, we want to find a spanning tree for which the combined weight of all its edges is minimized, denoted an MST in the sequel. Furthermore, we want to use a distributed algorithm to find that MST by placing a processor at each node and treating each edge as a bidirectional and error-free communication channel, over which the nodes can exchange messages among themselves. We assume that ini..