4,253 research outputs found
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Performance analysis of a broadcast star local area network with collision avoidance. Part 1, Infinite station population model
Packet collisions and their resolution create a performance bottleneck in random access LANs. As a solution to this problem, a broadcast star network with collision avoidance has been proposed and studied in [3 - 17]. In a broadcast star network, collisions of simultaneously transmitted packets are avoided by means of hardware called a collision avoidance switch. While the channel is being used by one station, the collision avoidance switch blocks other stations from using it. This network implements random access protocols without the penalty of collisions among packets and combines the benefits of random access (low delay when traffic is light; simple, distributed, and therefore robust protocols) with excellent network utilization.In this paper, we analyze the performance of a broadcast star network, assuming synchronous operation of a network. In synchronous operation, the channel time is slotted, and stations transmit only at the beginning of a slot. The number of stations on a network is assumed to be infinite, and packets arrive at stations according to a Poisson process. An exact analysis is developed, and the distribution for the transmission delays is obtained. It is also shown through simulations that a broadcast star operating under synchronous mode yields better performance than that operating under asynchronous mode, where transmissions of packets are not confined to the beginning of slots, and stations start transmission any time
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Issues in multi-media information networks
In an integrated service environment, where users exchange various types of aural and visual information, networks should appear friendly to its users providing tools for management of multi-media information. Networks should also efficiently satisfy diverse performance requirements of different information being exchanged.In this paper we present new architecture for integrated service networks being investigated and developed by the Distributed Computation and Communication Group at the Department of Computer Science in the Columbia University. Research efforts are devoted to developing both (1) document management software to allow users to manipulate and relate text/graphics/voice information in a dynamic way, and (2) a tree network architecture for reliable and efficient exchange of multi-media information
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Tree LANS with collision avoidance : protocol, switch architecture, and performance
Packet collisions and their resolution create a performance bottleneck in random access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the implementation of random access protocols without the penalty of collisions among packets. We review and compare the designs of some tree LANs that use collision avoidance switches. They have the potential of combining the benefits of random access (low delay when traffic is light, simple and distributed, and therefore robust, protocols) with excellent network utilization and concurrency of transmission. The collision avoidance LANs we review are broadcast star, Hubnet-like tree, Tinker-Tree, and a treenet that allows concurrent broadcasts within non-intersecting subtrees. After this review, we present a slotted-time, infinite user analysis of the broadcast star network
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Design implementation and measurement of a collision avoidance multiple broadcast tree network
Packet collisions and their resolution create a performance bottleneck in random access LANs. Collision avoidance switches are a hardware solution to this problem [1, 2]. Collision avoidance switches allow the implementation of random access protocols without the penalty of collisions among packets.In this paper, we describe a design and implementation of a local area network architecture based on collision avoidance, called the Collision Avoidance Multiple Broadcast (CAMB) tree network. Our implementation follows the protocol layering architecture of the IEEE 802 local area networks, and includes CAMB tree switches, station/network interface boards, and support of transport protocols. We also present the performance measurements of our experimental CAMB tree network
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A VLSI implementation of the collision avoidance switch protocol for CAMB tree LANs
To solve a performance bottle neck in random access LANs due to packet collisions and their resolution, collision avoidance switches are introduced. These switches allow random access protocols to achieve high performance by resolving collisions among packets. A conventional hardware implementation of these switches is the use of TTL chips. In this implementation; a handful of TTL chips are required to forma single switch (e.g., 18 TTL chips are needed for an implementation of the CAMB switch [7]). Thus, implementation of a complete network, which requires several of these switches, could very well result in a large and complex hardware system.Today's modern chip technology allows us to pack large quantity of logic in a single chip. By transferring the conventional implementation of the collision avoidance switches into a VLSI chip, the complexity of the resultant hardware is greatly reduced, not to mention the improvement in hardware performance and ease of packaging.This report provides an overall study of the collision avoidance protocols for the tree LANs with emphasis on the implementation of collision avoidance switches. Hardware implementations of sorne of these switches are discussed. And a VLSI implementation of the CAMB switch protocol is introduced
Cellular Automata Applications in Shortest Path Problem
Cellular Automata (CAs) are computational models that can capture the
essential features of systems in which global behavior emerges from the
collective effect of simple components, which interact locally. During the last
decades, CAs have been extensively used for mimicking several natural processes
and systems to find fine solutions in many complex hard to solve computer
science and engineering problems. Among them, the shortest path problem is one
of the most pronounced and highly studied problems that scientists have been
trying to tackle by using a plethora of methodologies and even unconventional
approaches. The proposed solutions are mainly justified by their ability to
provide a correct solution in a better time complexity than the renowned
Dijkstra's algorithm. Although there is a wide variety regarding the
algorithmic complexity of the algorithms suggested, spanning from simplistic
graph traversal algorithms to complex nature inspired and bio-mimicking
algorithms, in this chapter we focus on the successful application of CAs to
shortest path problem as found in various diverse disciplines like computer
science, swarm robotics, computer networks, decision science and biomimicking
of biological organisms' behaviour. In particular, an introduction on the first
CA-based algorithm tackling the shortest path problem is provided in detail.
After the short presentation of shortest path algorithms arriving from the
relaxization of the CAs principles, the application of the CA-based shortest
path definition on the coordinated motion of swarm robotics is also introduced.
Moreover, the CA based application of shortest path finding in computer
networks is presented in brief. Finally, a CA that models exactly the behavior
of a biological organism, namely the Physarum's behavior, finding the
minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From
software to wetware. Springer, 201
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