e 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 billing system is used to manage the receivables invoicing, payment, collection, and crediting functions and the billing support systems also includes billing data collection, mediation, and rating (see Figure 20.18). The key players in billing can be segregated under the following heads: Billing products: Companies like Amdocs, Telcordia, and Convergys are among the top players developing billing products for the telecom industry. Billing services: Service bureaus for billing offer both tier 1 and tier 2 services. Amdocs, CSG, and Convergys are among the top tier 1 service companies. There are many players offering tier 2 service-a few notable companies being Alltel, VeriSign, Intec, and Info Directions. Solution integrators: Billing integration is another hot area and Oracle is one of the leaders in telecom billing integration. Legacy/custom solution development and support: Some of the service pro- viders opt for custom solution development or relay on their legacy applica- tion to meet the billing needs. This is mainly attributed to the high level of security in content associated with billing and the company specific billing process that may not easily be satisfied by an off the shelf product. In house developers or developers from service and consulting companies are employed by the service provider initially to develop custom solutions and later to sup- port the solution. OSS/BSS Functions Customer 