U

UART (Universal Asynchronous Receiver/Transmitter)

A chip that is responsible for communications carried over a serial port; it converts between data bits and serial bits.

UDP (User Datagram Protocol)

A communications protocol that provides connectionless, unreliable communications services and operates at the transport layer of the OSI model. It requires a network-layer protocol such as IP to guide it to the destination host.

unbound media (or boundless media)

A term used to describe any media that do not have physical constraints. Examples of unbound media include infrared, wireless, and microwave. Compare with bound media.

UNC (Universal Naming Convention)

An industry naming standard for computers and resources that provides a common syntax that should work in most systems, including Windows, Unix, and NetWare. An example of a UNC name is \servernamesharename.

unicast

A network communication that is directed at a single network node. Unicast is the standard method of communication on a network.

UPS (uninterruptible power supply)

A system that provides protection against power surges and power outages. During blackouts, a UPS gives you time to shut down the network before the temporary power interruption becomes permanent. A UPS is also referred to as battery backup.

uptime

The amount of time that a device has been on and operating.

URL (uniform resource locator)

A name used to identify a site and subsequently a page on the Internet. An example of a URL is www.quepublishing.com/products.

USB (universal serial bus)

A type of interface between a computer system and peripheral devices. The USB interface allows you to add or remove devices without shutting down the computer. USB supports up to 127 devices.

user account

An account that an end user uses when logging in to a network. It contains the rights and permissions assigned to the user.

UTP (unshielded twisted-pair)

A type of cable that uses multiple twisted pairs of copper wire in a casing that does not provide much protection from EMI. The most common network cable in Ethernet networks, UTP is rated in categories including Category 1 through Category 5, as well as Category 5e and Category 6.