er data is passed on the primary, high-speed channels of the circuit. security Protection of information against unauthorized access or use. Segmentation and Reassembly sublayer A sublayer of the AAL that supports mapping between variable-length data units and ATM cells. selective ringing A system that has the capability of ringing only the desired subscriber's telephone on a multiparty line. Ringers tuned to one of five possible frequencies are used to achieve this effect. Semantic Web Tim Berners-Lee's latest project, which is focused on creating a universal medium for information exchange using refined indexing and searching-in other words, pro- viding meaning (semantics) to the content of documents in a manner that is understandable to machines. sensor mesh network A type of wireless micromesh network that uses many connected sen- sors to monitor a variety of factors. The sensors are all connected to each other and then to a base station. The sensors synchronize with each other, collect data, and sleep until the next iteration. server A processor that provides a specific service to the network. A routing server connects nodes and networks of like architectures, a gateway server connects nodes and networks of dif- ferent architectures, and so on. server-based network A network in which one computer is the repository (i.e., the server) and the other computers request information from and store information on the server. session A period of time in which an end user engages in dialog with an interactive computer system. session layer Layer 5 of the OSI model. It manages a logical connection between two com- munication points. set-top box A locally powered piece of cable equipment that resides in the subscriber's home and provides tuning, descrambling, and pay-per-view capabilities. SGSN (serving GPRS support node) A device that provides the packet-switched link to mobile stations in the mobile IMS architecture. The SGSN provides packet routing to and from the SGSN service area for all users in that service area.