Issues In Distributed Control For Atm Networks

Asynchronous Transfer Mode (ATM) network technology is expected to become a central part of the emerging global information infrastructure. ATM networks introduce a number of features that distinguish them from earlier technologies and introduce new issues in network control. This paper offers a framework for precisely defining and analyzing alternative approaches to the distributed control of ATM networks and explores some of the key design issues through a series of examples. It is hoped that it will provide a useful foundation for researchers in networking and distributed computing interested in exploring these issues further and developing more complete solutions. 0 This work was supported by the ARPA Computing Systems Technology Office, Ascom Timeplex, Bay Networks, Bell Northern Research, NEC, NTT, Southwestern Bell and Tektronix. ISSUES IN DISTRIBUTED CONTROL FOR ATM NETWORKS Jonathan S. Turner Washington University, St. Louis [email protected] 1. Introduction Asynchronous T..

Approximation algorithms for the shortest common superstring problem

AbstractThe object of the shortest common superstring problem (SCS) is to find the shortest possible string that contains every string in a given set as substrings. As the problem is NP-complete, approximation algorithms are of interest. The value of an aproximate solution to SCS is normally taken to be its length, and we seek algorithms that make the length as small as possible. A different measure is given by the sum of the overlaps between consecutive strings in a candidate solution. When considering this measure, the object is to find solutions that make it as large as possible. These two measures offer different ways of viewing the problem. While the two viewpoints are equivalent with respect to optimal solutions, they differ with respect to approximate solutions. We describe several approximation algorithms that produce solutions that are always within a factor of two of optimum with respect to the overlap measure. We also describe an efficient implementation of one of these, using McCreight's compact suffix tree construction algorithm. The worstcase running time is O(m log n) for small alphabets, where m is the sum of the lengths of all the strings in the set and n is the number of strings. For large alphabets, the algorithm can be implemented in O(m log m) time by using Sleator and Tarjan's lexicographic splay tree data structure

The Challenge of Multipoint Communication

The design of flexible communications systems, supporting a wide range of applications is the principal challenge facing the communications industry today. This paper focuses on the problem of multipoint communications, suitable for supporting such applications as entertainment video distribution, voice/video teleconferencing and LAN interconnection. We review the key issues involved in the design of multipoint communication networks, including switching system architecture, connection management, multipoint routing and congestion control. We conclude that flexible multipoint communications networks are technically feasible given current technology, and while there are many research issues requiring further study, it appears likely the cost of such networks may be only marginally higher than that of comparable point-to-point networks

Advanced Communications Systems

The Advanced Communication Systems Project is concerned with new communication technologies that can support a wide range of different communication applications in the context of large public networks. Communications networks in common use today have been tailored to specific applications and while they perform their assigned functions well, they are difficult to adapt to new uses. There currently are no general purpose networks, rather there are telephone networks, low-speed data networks and cable television networks. As new communications applications proliferate, it becomes clear that in the long term, a more flexible communications infrastructure will be needed. The Integrated Services Digital Network concept provides a first step in that direction. We concerned with the next generation of systems that will ultimately succeed ISDN. The main focus of the effort in the ACS project is a particular switching technology we call broadcast packet switching. The key attributes of this technology are (1) the ability to support connections of any data rate from a few bits per second to over 100 Mb/s, (2) the ability to support flexible multi-point connections suitable for entertainment video, LAN interconnection and voice/video teleconferencing, (3) the ability to efficiently support bursty information sources, (4) the ability to upgrade network performance incrementally as technology improves and (5) the separation of information transport functions from application-dependent functions so as to provide maximum flexibility for future services

Specification of Integrated Circuits for Broadcast Packet Network

The broadcast packet network is a form of communications network based on high speed packet switches with a flexible multi-point connection capability, making them suitable for a wide variety of applications. This paper gives preliminary specifications for the integrated circuits being designed for the prototype switching system to be constructed at Washington University

Terabit Burst Switching

This report summarizes progress on Washington University\u27s Terabit Burst Switching Project, supported by DARPA and Rome Air Force Laboratory. This project seeks to demonstrate the feasibility of Burst Switching, a new data communication service which can more effectively exploit the large bandwidths becoming available in WDM transmission systems, than conventional communication technologies like ATM and IP-based packet switching. Burst switching systems dynamically assign data bursts to channels in optical data links, using routing information carried in parallel control channels. The project will lead to the construction of a demonstration switch with throughput exceeding 200 Gb/s and scalable to over 10 Tb/s

A Methodology For Measuring Resilience in a Satellite-Based Communication Network

According to Presidential Policy Directive 21, increasing resilience of critical infrastructures is not only desired, but United States policy. Communications infrastructures are one such critical infrastructure. The purpose of this research is to develop a methodology for measuring resilience in satellite communication systems for use as a key criterion in the selection and acquisition of new satellite architectures, in accordance with the National Security Space Strategy. The base methodology utilized in this thesis is Extreme Event Modeling implemented through the use of Bi-Level Programming with monotonically nonlinear continuous and mixed integer variables. This model differs from previous efforts applied to other critical infrastructures in that it captures the temporal component associated with multiple events, as well as the repairs, or reconstitution, of infrastructure components. Furthermore, a heuristic based upon a ratio of impact to cost and local searches is developed to solve the resulting continuous bi-level problem

Almost All k-Colorable Graphs are easy to color

We describe a simple and efficient heuristic algorithm for the graph coloring problem and show that for all k greater or equal to 1, it finds an optimal coloring for almost all k-colorable graphs. We also show that an algorithm proposed by Brelaz and justified on experimental grounds optimally colors almost all k-O(n+m logk) time when n is the number of vertices and m the number of edges. The new implementation of Brelaz\u27s algorithm runs an O(mlogn) time. We observe that the popular greedy heuristic works poorly on k-colorable graphs

Advanced Communications Systems

The Advanced Communications Systems Project is concerned with new communication technologies that can support a wide range of different communication applications in the context of large public networks. Communication networks in common use today have been tailored to specific applications and while they perform their assigned functions well, they are difficult to adapt to new uses. There currently are no general purpose networks, rather there are telephone networks, low-speed data network and cable television networks. As new communication applications proliferate, it becomes clear that in the long term, a more flexible communication infrastructure will be needed. The Integrated Service Digital Network concept provides a first step in that direction. We are concerned with the next generation of systems that will ultimately succeed ISDN. The main focus of the effort in the ACS project is a particular switching technology we call broadcast packet switching. The key attributes of this technology are (1) the ability to support connections of any data rate from a few bits per second to over 100 Mb/s, (2) the ability to support flexible multi-point connections suitable for entertainment video, LAN interconnection and voice/video teleconferencing, (3) the ability to efficiently support bursty information sources, (4) the ability to upgrade network performance incrementally as technology improves and (5) the separation of information transport functions from applications-dependent functions so as to provide maximum flexibility for future services

Cocyclic Hadamard Matrices: An Efficient Search Based Algorithm

This dissertation serves as the culmination of three papers. “Counting the decimation classes of binary vectors with relatively prime fixed-density presents the first non-exhaustive decimation class counting algorithm. “A Novel Approach to Relatively Prime Fixed Density Bracelet Generation in Constant Amortized Time presents a novel lexicon for binary vectors based upon the Discrete Fourier Transform, and develops a bracelet generation method based upon the same. “A Novel Legendre Pair Generation Algorithm expands upon the bracelet generation algorithm and includes additional constraints imposed by Legendre Pairs. It further presents an efficient sorting and comparison algorithm based upon symmetric functions, as well as multiple unique Legendre Pairs