tailieunhanh - Mạng và viễn thông P28

Network Routing, Znterconnection and Znterworking The control of the routing of calls and connections (so-called ‘traffic’) across telecommunications networks is the most difficult but most important responsibility of a network operator. Only by careful planning and management of appropriate call and traffic routing plans can the network operator ensure successful connection of calls and the efficient use of network resources. | 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 28 Network Routing Interconnection and Interworking The control of the routing of calls and connections so-called traffic across telecommunications networks is the most difficult but most important responsibility of a network operator. Only by careful planning and management of appropriate call and traffic routing plans can the network operator ensure successful connection of calls and the efficient use of network resources. In this chapter we discuss the techniques used by network operators in establishing efficient call routing patterns and the special problems caused by network interconnection and interworking when calls or connections originated in one network have to be passed to another operator s network for completion. THE NEED FOR A NETWORK ROUTING PLAN We might choose laudable as it may seem to attempt to run our telecommunications network by completing as many calls as possible or delivering the greatest proportion of data messages. The problem is that if we attempt to do so we are bound adversely to affect the intelligibility of messages and the time it takes to deliver them. To attempt the complete if you can routing philosophy we simply programme the exchanges to route all messages any way possible rather than ever fail anything when a circuit is free. Unfortunately the network will perish of congestion and suffer appalling signal quality. Studying the scenario however is highly instructive and we shall look at an example or two shortly. The rational and rewarding alternative to the any way possible regime is to have network routing plan together with a supporting numbering plan. The appropriate routing algorithms laid out by the routing and numbering plans are selected to control network traffic and to comply with the overall constraints which the transmission plan and