Workshop

An essential part of a network interface card (NIC) that connects the network cable to the card.
Most 10BaseT cards have them built in; however, in some cases, you might have to get a
transceiver for an AUI port to connect to 10BaseT cable.
transport layer
Layer 4 of the OSI reference model. This layer controls the movement of data between systems,
defines the protocols for messages, and does error checking.
trap door
See back door.
Trivial File Transfer Protocol (TFTP)
An antiquated file transfer protocol now seldom used on the Internet. (TFTP is a lot like FTP
without authentication.) Frequently used for “diskless” booting from the network.
Trojan Horse
An application or code that, unbeknownst to the user, performs surreptitious and unauthorized
tasks that can compromise system security. (Also referred to as a Trojan.)
trusted system
An operating system or other system secure enough for use in environments where classified
information is warehoused.
tunneling
The practice of encapsulating one type of traffic within another type of traffic. For example, if you
only had a TCP/IP connection between two sites, you might tunnel IPX/SPX traffic within the
TCP/IP traffic. Nowadays, tunneling often implies employing encryption between two points, thus
shielding that data from others who may be surreptitiously sniffing the wire. These types of
tunneling procedures encrypt data within packets, making it extremely difficult for outsiders to
access such data.
twisted pair
A cable made up of one or more pairs of wires that are twisted to improve their electrical
performance.
User Datagram Protocol (UDP)
A connectionless protocol from the TCP/IP family. Connectionless protocols will transmit data
between two hosts even though those hosts do not currently have an active session. Such protocols
are considered “unreliable” because there’s no absolute guarantee that the data will arrive as it as
intended.
user
Anyone who uses a computer system or system resources.
user ID
In general, any value by which a user is identified, including his or her username. More
specifically, and in relation to UNIX and other multiuser environments, any process ID—usually a
numeric value—that identifies the owner of a particular process. See also owner and user.
UTP
Unshielded twisted pair. See also 10BaseT.
virtual private network (VPN)
VPN technology allows companies with leased lines to form a closed and secure circuit over the
Internet, between themselves. In this way, such companies ensure that data passed between them