mately, well-run call centers are nothing more than enormous routers. They receive incoming data, delivered using a variety of media (phone calls, e-mail messages, facsimile transmissions, mail order), and make decisions about handling them based on information contained in each message. One challenge that has always faced call center manage- ment is the ability to integrate message types and route them to a par- ticular agent based on specified decision-making criteria such as name, address, telephone number, e-mail address, Automatic Number Identifi- cation (ANI) triggers, product purchase history, the customer's geo- graphic location, or language preference. This has resulted in the development of a technical philosophy called unified messaging. With unified messaging, all incoming messages for a particular agent, regard- less of the media over which they are delivered, are housed centrally and clustered under a single account identifier. When the agent logs into the network, their PC lists all of the messages that have been received for them, giving them the ability to much more effectively manage the infor- mation contained in those messages. Today, unified messaging systems also support road warriors. A traveling employee can dial into a message gateway and download all messages- fax, e-mail-from that one central location, thus dra- matically simplifying the process of staying connected while away from the office. Call centers are undergoing tremendous change as the IP juggernaut hits them. The first of these is a redefinition of the market they serve. For the longest time, call centers have primarily served large corporations because they are expensive to deploy. With the arrival of IP, however, the cost is dropping precipitously, all major corporations are now moving toward an IP-enabled call center model because of the ability to create unified application sets and to introduce enormous flexibility into their calling models. Integrating the PBX There is an enormous installed base of legacy PBX equipment,