A dedicated Internet connection operating at 1.544 Mbps. Since it usually requires running a dedicated Ethernet or fiber optic line from a data center, it is very expensive ($500-$1200/mo.) and is therefore typically reserved for business use. Unlike cable modem and DSL connections, however, the bandwidth of a T1 line is guaranteed at all times.


Transmission Control Protocol. A connection-based protocol for use on IP networks. Its error-correction features guarantee that data will be delivered, and also that packets will arrive in the same order in which they were sent.


Transmission Control Protocol/Internet Protocol. A set of protocols used to connect computers on the Internet. Because it is so effective, TCP/IP is also sometimes used for LANs and is built into almost all operating systems.


A program that emulates a remote computer or device.

In the context of Internet connection sharing, the control panels of some cable/DSL routers must be accessed using telnet. Almost all operating systems include some sort of telnet program; in Windows, it can be accessed by opening the Run box and entering “telnet”.


Terms of Service. A legal contract that establishes rules for the use of a service. Most ISPs, for example, require their subscribers to agree to a ToS and can terminate the service if that agreement is violated.


Trivial File Transfer Protocol. A simple protocol that uses UDP connections (instead of more-prevalent TCP connections) to transfer data across a network. It is commonly used to update the firmware of cable/DSL routers.


The amount of data that can be transferred in a given amount of time. Usually expressed in bps (bits per second), Kbps, or Mbps. Synomyn for bandwidth.


The physical shape and arrangement of a LAN. There are three major types:

  • star topology - all devices are connected to a central hub or switch. This is the most popular configuration.
  • bus topology - all devices are connected to a central cable, called a backbone.
  • ring topology - all devices are connected to each other in a ring shape.

A type of cable in which two insulted wires are twisted around each other. One wire transmits data, while the other absorbs interference. Category 5 is an example of twisted-pair cabling.