 objects, which are The usual indicators are as follows: under the control of the management system. The system should have the facility for changing the configuration, initialising man- 1. Grade of service, which is a subjective measure of the satisfac- aged objects, shutting them down and removing them from service, tion expressed by the users of the service. collecting state information on a regular and on an on-demand basis, 2. Call completion rate, which is easier to measure, but which is and provisioning services and resources to meet demand. Examples dependent on factors such as the rapidity with which retries of such activities are: connecting end-to-end service; setting up occur, and the frequency of customer generated errors. alternative routing options under fault conditions; configuring gains 3. Network utilisation, both in terms of under utilisation, which on cards; providing alternative configurations depending on time of implies wasted investment, and over utilisation, which can day; and downline loading of information. result in congestion and delays. Network utilisation requires An important aspect of configuration management is name man- careful planning and control to enable overloads to be handled agement. This allows the user to symbolically name and refer to satisfactorily. resources on the network. Several techniques exist for this, the most 4. Return on investment, which is a prime measure. However, popular, and the ones for which ISO is developing standards, are although investment can be easily determined, return is much called the 'white pages' and 'yellow pages' protocols. In the white more complicated, since one needs to put monetary values on pages system the user looks up the values associated with any name, user frustration and time lost in getting through a congested in much the same way that the telephone numbers are associated network, and lost revenue due to customers taking their busi- with people's names on the white pages of a telephone directory. In ness elsewhere. yellow p