Tier-1. T1 is a data rate unit equivalent with 1,544 kbps. Used in North America and Japan. Also known as DS1 (Digital Signal level 1). Larger data units: T2/DS2 (6.312 Mbps), T3/DS3 (44.736 Mbps ).
Compare with E1. Also see PDH.

Transmission Control Protocol. TCP is a standard connection-oriented and reliable delivery protocol. TCP works at Layer 4 in the OSI model. TCP is used for connection establishment, data transfer and connection termination. TCP ensures that no packets are lost during transmission and packets are sent in correct order.
Also see OSI model.

Time Division Duplex. A duplexing technique which uses two separate time slots on the same frequency channel for downlink and uplink transmission. TDD enables operator to adjust downlink and uplink bandwidth dynamically based on user requirement. Therefore, it can support asymmetric traffic efficiently and is suitable for handling bursty data traffic. TDD is mostly deployed in license-exempt spectrum by WISP or independent service provider.
Contrast with FDD.

Time Division Multiplexing. A multiplexing technique in which signals are put in different time slots and each signal occupies full bandwidth.
Also see multiplexing. Compare with FDM.

Time Division Multiple Access. A multiple access technique in which signals from multiple stations are transmitted in sequence (or different time slots) using total bandwidth.
Also see multiple access. Compare with FDMA.

A DOS command for working on a computer remotely. It is also a standard Internet protocol that allows working on a remote computer (server) as if it were local. Telnet is a Layer 7 protocol.
Also see OSI model.

An adapter that connects serial cables ( e.g. RS-232, RS-422, RS-449, RS-485) to Ethernet ports.
Also see serial port, RS-232, and Ethernet.

The amount of data passing through a network from one node to another in a given time period.
Also see jitter and latency.

Telecommunications Industry Association. A trade association that works closely with EIA in producing telecommunication standards. The most well-known collaborative standard is TIA/EIA-568A "Commercial Building Telecommunications Wiring Standard".

TiVo refers to a device or a service that enables users to record favorite TV programming from cable TV or satellite TV channels by scheduling it in advance. A TiVo service requires a phone connection during setup and once the setup is done the TiVo box can be connected to a home network with broadband connection. The TiVo box comes with a uniquely designed remote control.

Temporal Key Integrity Protocol. An encryption protocol based on IEEE 802.11i specifications that changes the encryption key periodically to make it harder to crack. TKIP is intended to secure wireless LAN (Wi-Fi).
Also see Wi-Fi and WPA.

Transport Layer Security. A standard protocol that provides secure communications over the Internet using cryptography. TLS evolves from SSL.
Also see SSL.

An access method in which each node must wait for a passing token to start transmission. If a "wants-to-transmit" node is passed by the token, it processes the token and starts sending packet.
Other nodes compare the packet destination address with their addresses, if it matches a node's address then the node processes the token. When the process finishes, the node sends the token back to the network.
Network technologies that use token passing access method are Token Ring and FDDI.
Compare with contention and demand priority.

A LAN technology in which packet is carried by a token passing around all nodes in a closed loop. Supported data rates are 4 and 16 Mbps depending on the cable type. Token Ring implementation uses logical ring (physical star) topology. At its center is a MSAU, acting as the hub. There can be up to 33 MSAUs per ring.
Typical Token Ring network uses STP cable, but it may also use UTP or fiber optic cable. Maximum number of nodes in one ring is 260 for STP and 72 for UTP. Maximum cable length (from a node to MSAU) is 100 meters for STP and 45 meters for UTP.

The physical layout of all connections in a network. Topology describes how nodes in a network are interconnected to one another.
Also see bus, star, ring, and mesh topologies.

A device that works both as transmitter and receiver.

A device that transforms natural events like human speech into electrical signal that can be transmitted across telecommunication network.
Also see analog signal.

A transceiver that is carried by a satellite. Transponder links a satellite with its earth stations, that's receiving signal from an earth station (uplink), amplifying it, and retransmitting the signal to another earth station (downlink).

Layer 4 in the the OSI model. The Transport Layer is responsible for end-to-end transport between end users. This layer performs buffering, ordering, flow control, and error checking to make sure that data is received in the correct sequence and without error.
TCP and UDP are examples of Transport Layer protocols.
Also see OSI model.

Refers to integrated voice, video, and data services offered by established telcos or new service providers. Included in the triple play are new breeds of services, like VoIP, VoD, and IPTV.

The bus topology where each node is connected to the trunk using a drop cable. 10Base5 LAN (Thicknet) uses trunk/drop topology.
Also see bus topology.

A virtual pipe that connects two nodes (i.e. client computer and server) over a public network like the Internet. A tunnel is created by encapsulation and encryption of packets. Thereby, tunnel provides secure and private link across a public network. Physically, packets in a tunnel may take different routes in their travel to a destination node.
Also see VPN.

Two copper wires that are twisted around each other to minimize interference. Twisted pair cable is classified into several categories based on its design (i.e. wiring structure, number of wires, insulating material type) and its bandwidth. Twisted pair cables categories and their corresponding bandwidths and applications are as follows:

Cat 1, Cat 2, and Cat 4 are rarely used now. Cat 3 is still used for telephone cable. Cat 5 is the most widely used today in computer networks. While Cat 5e (Enhanced Cat 5) and Cat 6 are chosen for building future proof network cabling. Cat 7 is the newest type that is designed for high speed networks in more noise sensitive environments.
See picture. Also see UTP, ScTP, and STP.

Notation for Transmitter.