Showing papers on "Node (networking) published in 1971"

Optimal design of centralized computer networks

Abstract: Major design problems for centralized computer networks are link layout and capacity assignment. The objective is to select link locations and capacities so that the average time delay required to transmit a message from any node to the central node does not exceed a specified maximum. The design problem is to find the least cost system which satisfies the time delay constraints for given levels of traffic. In this paper, we describe an algorithm to select globally optimum link capacities for specified tree structures. We also give a heuristic method for finding low cost tree structures. The methods have been programmed and are capable of handling networks with thousands of nodes. In addition, they can consider any finite set of link capacities with an arbitrary cost structure and do not depend on the mathematical model used to calculate average time delay.

McROSS: a multi-computer programming system

Abstract: This paper describes an experimental "distributed" programming system which makes it possible to create multi-computer programs and to run them on computers connected by the ARPA computer network (ARPANET). The programming system, which is called McROSS (for Multi-Computer Route Oriented Simulation System), is an extension of a single-computer simulation system for modelling air traffic situations developed by Bolt, Beranek and Newman, Inc. (BBN) as a tool for air traffic control research. The McROSS system provides two basic capabilities. One is the ability to program air traffic simulations composed of a number of "parts" which run in geographically separated computers, the distributed parts forming the nodes of a "simulator network." The second is the ability of such a simulator network to permit programs running at arbitrary sites in the ARPANET to "attach" to particular nodes in it for the purpose of remotely monitoring or controlling the node's operation.

Determining the most vital link in a flow network

Abstract: : The most vital link in a single commodity flow network is that arc whose removal results in the greatest reduction in the value of the maximal flow in the network between a source node and a sink node. This paper develops an iterative labeling algorithm to determine the most vital link in the network. A necessary condition for an arc to be the most vital link is established and is employed to decrease the number of arcs which must be considered.

On maximal transitive subtournaments

Abstract: A tournamentTn consists of a finite set of nodes1, 2, …, n such that each pair of distinct nodes i and j is joined by exactly one of the arcsij or ji. If the arc ij is in Tn we say that i beats j or j loses to i and write i→j. If each node of a subtournament A beats each node of a subtournament B we write A→B and let A + B denote the tournament determined by the nodes of A and B.

Looped direct switching system

Abstract: A communication system for transmitting messages between calling and called parties wherein the message is divided into predetermined length blocks and transmitted a block at a time. The concept includes the possibility of a very complex system wherein the message is transmitted via communication links from one node to the next node such that the transmitting party does not have a solid connection to the ultimate receiving party. In other words the transmission of a block from one node to the next is completed and satisfactory receipt is acknowledged before the message block is transmitted to a further node. The message blocks can be transmitted at a time when some of the nodes connecting the calling and called parties are busy with other messages such that the message block is stored in each node of the connection path until the following node is clear to receive a new message block.

Cost Minimization in Networks with Discrete Stochastic Requirements

Abstract: Multistage minimum-cost network-flow analysis solves many practical problems in production-inventory-distribution, marketing, personnel, and finance. Unlike previous network papers, which generally restricted themselves to a deterministic situation, this paper investigates the stochastic environment. Starting from the standard multistage network-flow problem, we create a stochastic network by permitting the node requirements to be discrete random variables with known conditional probability distributions. Our goal is to determine the minimum-expected-cost flow and thereby solve the problem. Although linear programming under uncertainty can determine this flow, it would ignore the special structure of network-flow problems that allows development of computationally efficient algorithms. In this paper, we instead exploit the underlying network structure to produce both a new structure that is not a network but maintains many of the properties of a network, and a new node that replicates flows instead of conserving them. The new nodes, called replication nodes, together with the new structure, allow the development of an efficient computational algorithm that is capable of solving problems much larger than those solvable by linear programming under uncertainty.

A multipath traffic assignment model

Abstract: THE MECHANICS OF A TRAFFIC ASSIGNMENT MODEL THAT IS ABLE TO ASSIGN COTERMINOUS TRIPS TO ALTERNATIVE ROUTES WITHOUT RESORTING TO REITERATION OR PATH ENUMERATION ARE DESCRIBED. UNDER A PARTICULAR DEFINITION OF "REASONABLE PATH," THE MODEL SATISFIES CERTAIN COMMON-SENSE REQUIREMENTS. THE MODEL IS A 2-PASS MARKOV MODEL. IT CALCULATES NODE AND LINK TRANSITION POSSIBILITIES IN ONE EXAMINATION OF THE NETWORK AND ASSIGNS TRIPS IN A SECOND EXAMINATION, WHEN IT DIVERTS TRIPS ENTERING A NODE TO ALL REASONABLE LINKS ENDING AT THE NODE. THE MODEL NEVER EXPLICITLY EXAMINES A PATH, AND IT IS NOT IN ANY SENSE AN OPTIMIZATION MODEL. IT ASSIGNS TRIPS TO ALL REASONABLE PATHS SIMULTANEOUSLY IN SUCH A WAY THAT THE RESULTING EFFECT IS IDENTICAL TO WHAT WOULD HAVE BEEN OBTAINED HAD EACH PATH BEEN ASSIGNED TRIPS SEPARATELY UNDER CERTAIN CHOICE PROBABILITY ASSUMPTIONS. THUS, COMPARED TO OTHER MULTIPATH ASSIGNMENT TECHNIQUES, THE MODEL IS THEORETICALLY ATTRACTIVE AND COMPUTATIONALLY VERY EFFICIENT. TWO ALGORITHMS ARE ALSO PRESENTED THAT DIFFER IN THEIR DEFINITION OF A REASONABLE PATH, AND IN THE NUMBER OF TIMES EACH IS EXECUTED TO ASSIGN ALL TRIPS FROM A GIVEN ORIGIN NODE. /AUTHOR/

Nodal Blocking in Large Networks

Abstract: : A theoretical study is given for store-and-forward communication networks in which the nodes have finite storage capacity for messages. A node is blocked when its storage is filled, otherwise it is free. A two-state Markov model is proposed for each node, and the fraction of blocked nodes in the network is shown also to have a two-state Markov process representation. The time-dependent probability that any given node in the network is blocked is obtained for some uniform networks of arbitrary dimension, and various results describe the clumping phenomena in these networks. Through a modification of the basic Markovian network model, the fraction of blocked nodes in a computer- simulated store-and-forward communication network is predicted with reasonable accuracy.

A constrained maximum flow problem

Abstract: We consider the problem of maximizing the flow from one node to another in an oriented network subject to flow conservation and capacity limitation constraints and the additional constraint that for some nodes a certain positive linear combination of flows entering the node is bounded. Several properties of solutions to this problem are developed and a heuristic method for its solution is presented.

An Optimization Problem in Communication Nets

Abstract: An optimal distribution tree with respect to a node of a nonoriented communication net is defined as a tree such that the distribution cost from the reference node to any other node in the net is a minimum. The paper presents an effective method for determining such a tree. The effectiveness of this method lies in the facts that (i) all the paths of an optimal distribution tree can be determined simultaneously and (ii) because of the recurrence nature of the method, the solution can be obtained very easily by hand for simple problems and can be conveniently adapted for machine computation for complex networks. A repeated application of this method enables one to determine an optimal distribution center of a given net.

Decentralized Transshipment Networks

Abstract: In the usual formulation of the transshipment problem it is assumed that a single decision-maker is dealing with a unified network of nodes and arcs and that supply and demand levels at each source are determined a priori. This paper develops a transshipment model in which subnetworks are controlled by a decentralized management level and supply levels at each source node are to be determined by a central manager.