 capacity for each device connected to it. It tandem central offices operates either on a first-come, first-served basis or on a priority basis in which certain Used in the core of traditional, traditional streams of traffic have higher priority than Public Switched Telephone Networks others. (PSTNs). Tandem central offices switch traf- fic between central offices. End users are not streaming video and audio connected to tandem offices. Tandem cen- A means of starting to play a message while tral offices are being replaced by lower-cost, the rest of it is being received. Streaming uses more efficient softswitches. compression to make the voice, video, and data files smaller SO that they can be transmit- TCP (Transmission Control Protocol) ted in less time. Streaming video and audio Includes sequence numbers for each packet is used in broadcasting video and audio over SO that the packets can be reassembled at the Internet. their destination. The sequence numbers ensure that all of the packets arrive and are switching assembled in the proper order. If some pack- Equipment with input and output ports that ets are discarded because of congestion, the transmits traffic and sets up paths to desti- network retransmits them. The numbering nations based on digits dialed or addressing bits. and tracking of packets make TCP a connec- tion-oriented protocol. Router-based LAN T.120 internetworking uses TCP. The ITU-defined standard for document sharing and white boarding. People using TCP/IP (Transmission Control Proto- T.120-adherent software can participate in col/Internet Protocol) document-sharing conferences with one The suite of protocols used on the Internet another over the Internet. For example, and also by organizations for communica- vendors can demonstrate their products to tions among multiple networks. Glossary TD-SCDMA (Time-Division Synchro- network, the configuration in which lines are nous Code-Division Multiple Access) connected to one another. China Mobile uses TD-SCDMA, which is a homegrown version of UMT