Terminal Adapter (TA) A device that connects non-compatible ISDN devices to an ISDN network. If a TA is used for an ISDN dialup connection, then it can be thought of as a modem. If a TA is used to connect a device to a LAN, then it can be thought of as a network interface card. It should be noted that although a TA is frequently referred to as an ISDN modem or digital modem in the context of an ISDN dialup connection, this reference is incorrect. By definition, a modem performs analog-to-digital and digital-to-analog conversions. Since ISDN is completely digital, no such conversions are necessary, which makes the expressions, ISDN modem or digital modem, incongruous. Terminator Layer 1 device that prevents signal reflections by providing electrical resistance at the end of a cable to “absorb” signals to keep them from bouncing back and being heard again by the devices connected to the cable. Thick Ethernet Describes IEEE 802.3 10BASE5, which uses “thick” coaxial cable (outer diameter between 0.375-inch and 0.405-inch) as its physical medium. Thin Ethernet Describes IEEE 802.3 10BASE2, which uses “thin” coaxial cable (outer diameter between 0.175-inch and 0.195-inch) as its physical medium. Threat Assessment An activity that involves determining how much security is necessary for proper control of system and network assets. Threat assessment is guided by answering the overriding question, “What assets are critical to the operation of my network and who do I think would want access to them?” Throughput A realistic measure of the amount of data transmitted between two nodes in a given time period. It is a function of hardware/software speed, CPU
310 310 power, overhead, and many other items. Compared to bandwidth , throughput is what the channel really achieves, where bandwidth is what is theoretically possible. Time Division Multiplexing (TDM) A multiplexing technique that assigns to each node connected to a channel an identification number and a small amount of time in which to transmit. TDM-based transmissions are serially sequenced. Token A special frame on a token ring or token bus network. Possession of the token permits a node to transmit data. Token Bus A local area network technology based on a token-passing protocol for media access. Defined in IEEE 802.4. A token bus network is characterized as a logical ring on a physical bus—physically, the network resembles a bus topology, but logically, the network is arranged as a ring with respect to passing the token from node to node. Token Passing Protocol A network protocol that requires nodes to first possess a special frame, called a token , prior to transmitting data. Token-passing schemes are both contention-free and collision-free. Token Ring A local area network technology based on a token-passing protocol for media access control. Defined by IEEE 802.5. A token ring LAN is implemented either as a logical ring using a physical ring topology, or as a logical ring structure arranged in a physical star configuration.
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