 strengthen customer relationships, improve long-term business health, cement customer loyalty, and gener- ally make businesses more competitive. However, for billing to achieve its maximum benefit and strategic value, it must be fully integrated with a company's other operations support systems, including network and ser- vice provisioning systems, installation support, repair, network manage- ment, and sales and marketing. If done properly, the billing system becomes an integral component of a service suite that allows the service provider to quickly and efficiently introduce new and improved services in logical bundles; improve business indicators such as service timeliness, billing accuracy, and cost; offer custom service programs to individual Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Telephony Chapter 3 customers based on individual service profiles; and transparently migrate from legacy service platforms to the so-called next generation network. In order for billing as a strategic service to work successfully, service providers must build a business plan and migration strategy that takes into account integration with existing operations support systems; busi- ness process interaction; the role of IT personnel and processes; and postimplementation testing to ensure compliance with strategic goals stipulated at the beginning of the project. VoIP Supporting Protocols In addition to IP, VoIP relies on a superset of additional protocols to guar- antee the level of rich functionality that users have come to expect. The relative importance of the protocols discussed in the sections that follow wax and wane like the stages of the moon, but all are important and readers should be familiar with them. H.323 H.323 started in 1996 as H.320, an ITU-T standard for the transmission of multimedia content over ISDN. Its original goal was to conne