Connection Admission Control the net that likes to say YES! No network operator likes to turn away business; if it does so too often customers are likely to take their business elsewhere. Yet if the operator always accepts any connection request, the network may become congested, unable to meet the negotiated performance objectives for the connections already established, with the likely outcome that many customers will take their business elsewhere. | Introduction to IP and ATM Design Performance With Applications Analysis Software Second Edition. J M Pitts J A Schormans Copyright 2000 John Wiley Sons Ltd ISBNs 0-471-49187-X Hardback 0-470-84166-4 Electronic 10 Connection Admission Control the net that likes to say YES No network operator likes to turn away business if it does so too often customers are likely to take their business elsewhere. Yet if the operator always accepts any connection request the network may become congested unable to meet the negotiated performance objectives for the connections already established with the likely outcome that many customers will take their business elsewhere. Connection admission control CAC is the name for that mechanism which has to decide whether or not the bandwidth and performance requirements of a new connection can be supported by the network in addition to those of the connections already established. If the new connection is accepted then the bandwidth and performance requirements form a traffic contract between the user and the network. We have seen in Chapter 9 the impact that changes in traffic parameter values have on performance whether it is the duration of a peak-rate burst or the actual cell rate of a state. It is important then for the network to be able to ensure that the traffic does not exceed its negotiated parameter values. This is the function of usage parameter control. This in turn ensures that the network meets the performance requirements for all the connections it has admitted. Together connection admission control and usage parameter control UPC are the main components in a traffic control framework which aims to prevent congestion occurring. Congestion is defined as a state of network elements such as switching nodes and transmission links in which the network is not able to meet the negotiated performance objectives. Note that congestion is to be distinguished from queue saturation which may happen while still remaining within the .
