n trunk connections and the LAN/WAN. The customer money saved using a distributed or dispersed IPT system solution for multiple-premises communications requirements can be substantial, and a single-system design can also provide significantly enhanced performance and operating benefits. Using an IP PBX system design that supports multiple locations allows advanced features such as station user roaming and automatic call distribution to be accessed and implemented by system subscribers, regardless of their physical location. This con- tributes to the enhanced performance potential of the single distributed system solution with local survivability options. Open-Source PBXs The theory behind open source is that too many cooks actually improve the broth. Widespread peer review finds and fixes bugs faster than the efforts of a smaller, albeit dedicated, project team. The result is often more robust software, lower support costs, and more rapid innovation. Of course, this Chapter 9 IP Services challenges the established IP PBX pricing model while facilitating standards-based cooperation. However, customer concerns about product schedules and quality detract from trust in the open-source model. Service Provider VolP Solutions The three major approaches to service provider VoIP solutions are IP centrex, hosted PBX, and virtual PBX services, such as pro- vider-managed call servers, application servers, and media gateways. The main driver of service provider VoIP solutions is reducing the enterprise administration and reducing capital expenditures. Voice quality is often compara- ble to that in the PSTN. But the greatest benefit is the cost-efficient bundling of voice, Internet access, and enhanced features, including an auto-attendant, a Web- based dashboard for each user and administrator, integrated messaging (e.g., voice- mail as e-mail file attachments), redirection to other phones, and simultaneous ringing of up to 10 phones. Standards for IP Voice Before we talk about the standards for IP voice, we need to discuss t