through communications lines, generally measured in bits per second. transmit To send information from one location to another. transparent bridging A system in which a bridge functions as a node on each of the con- nected networks, and its presence in the communications path between nodes is transparent. Communication proceeds as if the nodes were on the same network. transponder The receiver, transmitter, and antenna equipment that forms a single repeater channel on a satellite. transport layer transport layer Layer 4 of the OSI model, which provides reliable, transparent transfer of data between endpoints. tree A type of bus network topology in which the medium branches at certain points along its length to connect stations or clusters of stations; also called a branching bus. triple-play services A service provider's bundle of voice, data, and video/TV services, deliv- ered over the same infrastructure. troubleshooting Monitoring and testing the performance of a network to detect and fix problems. trunk A circuit that is configured to support the calling loads generated by a group of users; the transmission facility that ties together switching systems. TTC (Telecommunications Technology Committee) A body that creates telecommu- nications standards that are followed in Japan. tunneling The encapsulation of one protocol within another. Tunneling is often used to transport a LAN protocol across a backbone network that does not support the LAN protocol. turnkey system A complete communications system, including hardware and software, that is assembled and installed by a vendor and sold as a total package. twisted-pair cable A cable that consists of two insulated wires twisted around each other (and sometimes wrapped in additional insulation to help shield the signals from electromagnetic noise). Twisted-pair cable is often used in telephone wires; it also serves as the transmission medium in some LANs. Twofish A very strong encryption algorithm that was one of the five initial candidates for AES. two-wire circui