tructure convergence, device convergence, and applications convergence. conversion The process of changing from one method to another. It may refer to changing processing methods, data, or systems. COPS (Common Open Policy Service) An IETF query/response-based client/server tocol for supporting policy control. It addresses how servers and clients on a network exchange policy information, and it transmits information between a policy server and its clients, which are policy-aware devices such as switches. core The central part of a network. CoS (class of service) A categorization of subscribers or traffic according to priority levels. Network resources are allocated based on the CoS. CPE (customer premises equipment) Equipment that is located at the customer pre- mises and is owned and managed by the customer. CR (cognitive radio) A forthcoming device that can seamlessly switch call and transmission modes to whatever makes the most sense, given the location at a given time, whether cellular, Wi-Fi, or VoIP. CR is a smart system in which a radio device and its antenna can adapt their spec- trum use in response to their operating environment, including the radio frequency spectrum, user behavior, and network state. CRC (cyclic redundancy check) A powerful error-detecting technique. By using a poly- nomial, a series of two 8-bit block-check characters are generated that represent the entire block of data. The block-check characters are incorporated into the transmission frame and then checked at the receiving end. CR-LDP (Constraint-Based Routed Label Distribution Protocol) A protocol in the MPLS architecture that can set up paths to meet traffic-engineering requirements. crossbar switch A switch that has a crosspoint for each input/output pair, and only one con- tact pair needs to be closed to establish an input to output connection. crosstalk Interference or an unwanted signal from one transmission circuit detected on another, usually parallel, circuit. CRTP (Compressed Real-Time Transport Protocol) RTP compression