 charge is then calculated by applying discounts, taxes, promotions, and other parameters that impact the final bill to customer but may not be directly linked to usage. Let us now take a specific example of how a call is rated. The following are the high level steps: 1. Determine originating charge point: The originating point would include the country code, city code, and exchange number. The originating cell site address is identified in this step. 2. Terminating charge point: The terminating cell site address is computed where the terminating number will also be a combination of country code, city code, and exchange number. 3. Determine the duration of the call. 4. Determine the rate plan to be applied. The band could be based on networks (fixed or mobile), TOD, DOW, terminating network, and SO on. 5. Based on the rate plan, the rate table lookup is done. This could be based on the rate table ID assuming the table id can identify specific plans. 6. Apply the rate plan on the usage to compute the rate. 7. Apply any other charges like discounts on the rate to determine the customer payable for the call. In short, rating mainly loads the transactions, does a lookup on external data, then applies the business rules and routes the rated transactions to accounting for bill settlement. Figure 20.17 shows that the interaction of other OSS modules with rating engine. Some of the key players developing stand-alone rating solutions include RateIntegration, OpenNet, Am-Beo, Boldworks, Highdeal, and Redknee. There is more competition in mediation space, where some of the key players are Ventraq (combined companies of ACE*COMM, TeleSciences, and 10e Solutions), Comptel, HP, Ericsson, and Intec. Fundamentals of EMS, NMS and OSS/BSS Account information for settlement Communicate rating plan Partners Accounting Content charges Rating engine Historical usage Service provision for a rating plan Usage records Archival Provisioning Mediation Fraud Planning management Figure 20.17 Interactions with rating engine. To summarize, the