of the features that are available offer greater flexibility than those available on analog telephones. Customers have the option of having calls ring on both their mobile and landline telephone numbers without giving out their mobile numbers. They can also opt to receive their voicemail messages in their e-mail inboxes. Moreover, many smaller providers as well as some larger traditional ones are using their centralized VoIP platforms to offer the hosted telephone service described in Chapter 2, "Data Centers and Internet Protocol Private Branch Exchanges." With hosted telephone service, also referred to as IP Centrex, the VoIP infrastructure is located at the provider's site rather than at the customer's site. Scott Hoffpauir, chief technology officer and cofounder of BroadSoft, a VoIP software company for mobile and wireline networks, believes that IP Centrex sales to small and midsize enterprises were booming even during the 2009 recession because customers recognized the sav- ings in outsourcing their phone systems. Centralized VolP Services Architecture Carriers support centralized packetized voice (VoIP) and enhanced applications such as unified messaging as well as voice and video conferencing in their core networks. Centralization has been made possible by the high-speed fiber-optic networks that Convergence in Core and Metropolitan Networks connect broadband customers to long-haul networks. This phenomenon is similar to the Internet and cloud models in which applications are also supported centrally. VoIP servers are based on standard computer processors and open-standards protocols. Softswitches and Gateways Softswitches process calls, provide routing for calls, transfer control of calls to other networks, and interface with billing systems. Processing calls involves setting up, transferring, and ending calls. In the early 2000s, application servers (described later) were generally referred to as softswitches. This has changed as these servers now hold more applications. Media gateways described in this