e reservations. It also supports smooth rerouting of label-switched paths, preemption, and loop detection. RTCP (Real-Time Transport Control Protocol) An ITU protocol that provides status feedback from senders to receivers. RTCP XR (RTCP Reporting Extension) An emerging media transport standard that allows information hidden by SRTP to be extracted directly from the digital signal processor software and IP phones and gateways and reported directly in the RTCP XR message. RTMP (Routing Table Maintenance Protocol) A communication protocol AppleTalk to ensure that all routers on the network have consistent routing information. Glossary RTP (Real-Time Transport Protocol) RTP (Real-Time Transport Protocol) An Internet protocol for transmitting real-time data such as audio and video. RTP itself does not guarantee real-time delivery of data, but it does pro- vide mechanisms for the sending and receiving applications to support streaming data. RTSP (Real-Time Streaming Protocol) A protocol that runs on top of IP multicasting, UDP, RTP, and RTCP. sampling A statistical procedure whereby generalizations are drawn from a relatively small number of observations. SAN (storage area network) A network designed to attach computer storage devices such as disk array controllers and tape libraries to servers. SANs are common in enterprise storage. satellite communications The use of orbiting satellites to relay transmissions from one earth station to another or to multiple earth stations. scattering A cause of lightwave signal loss in optical fiber transmission. Diffusion of a light beam is caused by microscopic variations in the material density of the transmission medium. SCP (service control point) A centralized node that contains service logic for the manage- ment of a call. scrambler A coding device that is applied to a digital channel to produce an apparently ran- dom bit sequence. A corresponding device is used to decode the channel (i.e., the coding is reversible). ScTP (screened twisted-pair) STP cabling with metal shieldi