ers are not connected to tandem offices. Tandem central offices are being replaced by lower-cost, more efficient softswitches. TCP (Transmission Control Protocol) Includes sequence numbers for each packet SO that the packets can be reassembled at their destination. The sequence numbers ensure that all of the packets arrive and are assembled in the proper order. If some packets are discarded because of congestion, the network retransmits them. The numbering and tracking of www.TechnicalPDF.com packets make TCP a connection-oriented protocol. Router-based LAN internetworking uses TCP. TCP/IP (Transmission Control Protocol/Internet Protocol) The suite of protocols used on the Internet and also by organizations for communications among multiple networks. TD-SCDMA (Time-Division Synchronous Code- Division Multiple Access) China Mobile uses TD-SCDMA, which is a homegrown version of UMTS TDD (3G mobile protocol), for its 3G mobile service. tether The ability to connect laptop or tablet computers that don't have Internet access to the Internet via a mobile handset's Internet connection. This is generally done by connecting the computer and mobile handset together through USB ports via USB-compatible cables. throughput The actual amount of user data that can be transmitted on a telecommunications link or on wireless networks. Throughput does not include headers, for example, bits used for addressing, error correction, or prioritizing packets with voice and data bits. tier 1 provider A loosely defined term for Internet service providers that own Internet backbone fiber-optic facilities in addition to ISP services such as hosting and e-mail. Examples include AT&T, Level 3, Sprint Nextel, and Verizon. TDM (Time-Division Multiplexing) TDMs, such as T1/E1 equipment, save capacity for each device that is connected to the multiplexer. This is less efficient than other methods such as statistical www.TechnicalPDF.com multiplexing because capacity is unused when the device is not transmitting. topology The geometric shape of the p