 where policy servers authorize and commit these QoS requests. PacketCable 1.5 PacketCable 1.5 supersedes previous versions (1.1, 1.2, and 1.3) and consists of additional capabilities. It consists of 21 specifications and 1 techni- cal report that define the call signaling, QoS, codec, client provisioning, billing, message collection, PSTN interconnection, and security interfaces necessary to implement a single-zone or multizone PacketCable solution for residential IP voice services. PacketCable 2.0 PacketCable 2.0 will replace MGCP with SIP. (The MGCP and SIP protocols are discussed in Chapter 9.) OpenCable Digital cable TV devices present another exciting area to watch in the coming years. The goal of the CableLabs OpenCable program (www.opencable.org) is to publish specifications that define digital cable network interfaces, as well as nature of next-generation cable set-top boxes. CableLabs started the OpenCable initiative in 1997, with the goal of helping the cable industry deploy interactive services over cable, creating a common standard for digital cable TV within the United States, and promoting competition among licensed device manufacturers. OpenCable has two key components: a hardware specification and a software specification. The hardware specification describes a receiver that ensures interop- erability and can be sold at retail. The software specification, called the OpenCable Applications Platform (OCAP), creates a common platform on which interactive services can be deployed. The following sections describe these two components. OpenCable Hardware The CableLabs cable modem standard MCNS will be used with OpenCable set-top boxes, with advanced digital video compression cir- cuitry to create terminals capable of supporting next-generation video and the entire range of current and future Internet and Web-based applications. The OpenCable effort is seen as the linchpin of the cable industry's digital future. It is independent of the processor and operating system. Compliant set-top boxes must allow 