U

UA: User Agent

UCB: University of California at Berkeley

UBR: Unspecified Bit Rate; An ATMservice type in which the ATM network makes a 'besteffort' to meet the transmitter's bandwidth requirements.

UDP: User Datagram Protocol

UE: User Element

UFR: Unspecified Frame Rate; one of Frame Relay'sanswers to QoS.

UFS: _ File System

UI: Unix International

UMTS: Universal Mobile TelecommunicationsSystem

UNI: User Network Interface

unicast: Message sent to a single networkdestination. Compare with broadcast and multicast.

unicast address: Address specifyinga single network device. Compare with broadcastaddress and multicast address. Seealso unicast.

UNICOS: Unix version offered by Cray, (CrayResearch, Inc.)

UNIX: THE computer operating system (the basicsystem software running on a computer, underneath things like any variousand sundry application programs). UNIX is designed to be used by many peopleat the same time (it is multi-user) and each of those people can be doingmany things at the same time (it is multi-tasking) and has TCP/IP built-in.It is the most common operating system for servers on the Internet.

UNMA: Unified Network Management Architecture

UPE:

URL: Uniform Resource Locator, (WWW)

USB: Universal Serial Bus; a new external busstandard that supports data transfer rates of 12 Mbps (12 million bitsper second). A single USB port can be used to connect up to 127 peripheraldevices, such as mice, modems, and keyboards. USB also supports Plug-and-Playinstallation and hot plugging.  Starting in 1996, a few computer manufacturersstarted including USB support in their new machines.  Since the releaseof Intel's 440LX chipset in 1997, USB has become more widespread. It isexpected to eventually completely replace serial and parallel ports. (seealso IEEE 1394)

USSB: United States Satellite Broadcasting,(USSB Channel 1)(www.ussb.com)

UTC: Universal Time Coordinated

UTP: Unshielded Twisted Pair

UTS: Version of Unix provided by Amdahl.

UUCP: Unix to Unix Copy Program / Protocol

UUNet: UNIX to UNIX Network; The first commercialInternet service provider, headquartered in Fairfax, VA. The company (www.us.uu.net)was founded in 1987 by Rick Adams, one of the original developers of ARPAnet,the precursor to the Internet. In 1996, UUNET merged with MFS Communications,Inc., and later that year, WorldCom acquired both MFS and UUNET. In 1998,WorldCom acquired Advanced Network Services (ANS) andCompuServe Network Services. UUNET is now a full-service provider.

UVSG: United Video Satellite Group