tailieunhanh - Mạng và viễn thông P32

Network Trafic Control Traffic control is as much art as it is science, and the profits are gratifying. The right control mechanisms and routing algorithms in the right places will determine the overall performance and efficiency of our network. What is more, they will giveus simpler administration, better management and lower costs. This chapter describes a number of these admirable devices: first the simple methodscommonlyusedforoptimizingnetworkroutingundertypical‘normal-dayloading’ conditions; then we look at recent more powerful and complex techniques, together with some of the practical complications facing telecommunications today. . | Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic 32 Network Traffic Control Traffic control is as much art as it is science and the profits are gratifying. The right control mechanisms and routing algorithms in the right places will determine the overall performance and efficiency of our network. What is more they will give us simpler administration better management and lower costs. This chapter describes a number of these admirable devices first the simple methods commonly used for optimizing network routing under typical normal-day loading conditions then we look at recent more powerful and complex techniques together with some of the practical complications facing telecommunications today. Finally we note how several network operators have found ways of interconnecting with the multiple carriers that have emerged lately as a result of market deregulation. NETWORKS Any metropolitan international trunk transit or corporate network by virtue of its nature and sheer size has to include a considerable number of switches exchanges . If there are many inter-connections between these switches any individual call crossing the network will have plenty of alternative paths open to it. It is in fact the number of path permutations which determines the robustness of the network to individual link failure and sets the level or grade of service provided . the probability of successful call connection . It offers the customer what he most wants an acceptable chance of making a successful call or information transfer each time. Particular attention must be paid to choosing the call-control mechanisms which are going to determine the routing of our customers individual calls connections or messages bearing in mind that in an ideal network we aim overall to achieve a controlled flow of traffic throughout the network at reasonable cost and .