e exchange - whether immediate or delayed - is directed to the appropriate destination in the OSS at the NOC through a visual computer display, a file, a mailbox, a printer or a combination of media. 2.3 Traffic Management In addition to the basic functions of managing the local exchanges and managing other NEs, an OSS has functions for traffic measurement and gathering of statistics. Measurement results can be processed, stored and displayed to form the basis of traffic and resource planning performed in an OMC. Traffic management is simpler at the OMC level than at the NOC level. At the OMC level, the following types of traffic are measured: local subscribers to subscribers in the same exchange, or local calls local subscribers to subscribers in another exchange, or outgoing trunk calls subscribers in another exchange to local subscribers, or incoming trunk calls transit calls, which are a through-connection between a pair of subscribers, both of whom are outside the local exchange. At the NOC level, there are more views of network traffic and more statistics to consider because any NOC is responsible for regions covered by several OMCs. 2.3.1 Measuring Traffic Distribution Traffic distribution is the relative amount of traffic along different paths, shown in Figure 2.6. In particular, the distribution of traffic along different paths between a particular pair of exchanges will be of interest, such as link 1 link 4 versus link 1 link 2 link 3 between Exchanges 1 and 2 in Figure 2.6. By shifting traffic from one path to another, the traffic distribution might be evened out while the overall result of traffic passing between Exchanges 1 and 2 is unchanged. OSS for Telecom Networks link 1 Exchange 1 link 2 link 4 link 5 link 3 Exchange 3 Exchange 2 link 6 Exchange 4 Figure 2.6 Alternative paths for the same endpoints. Most exchanges have traffic measurement functionality. Measurement is initiated by the OSS and log files are received and processed by a traffic management module in the OSS where the results can be 