|
| Glossary
of Selected Terms (U-Z) |
| |
| Section
U |
| unbalanced
transmission Telecommunications transmission across
metallic conductors (i.e. wire pairs) in which the two conductors
do not play an equal role. (e.g. 75 ohm coaxial cabling) |
| UDP
(user datagram protocol) A transport protocol of the
IP-suite (and alternative to TCP). UDP provides an unreliable
and connectionless transport service. |
| UMTS
(universal mobile telephone service) The most modern
type of mobile telephone network, which is designed to be capable
of efficient carriage both of telephone calls and high speed
data messages. |
| unicode
A binary coding scheme using 16-bit binary values to represent
textual characters. It was developed as an extension of the
ASCII code to include all possible international characters.
|
| URL
(uniform resource locator) A fancy name for a Worldwide
Web address in the form http://www.company.com |
| usage
parameter control (UPC) The execution of appropriate
action when negotiated values of information transfer are exceeded.
|
| user-network
interface (UNI) The interface (physical interface and
protocols) between a user's terminal equipment and the network.
|
| user
plane A conceptual end-to-end communications connection
between user terminal equipments for communicating user information
(i.e. the useful information content of a communications session).
UTP (unshielded twisted pair) Term applied particularly to indoor
cabling of a type in which twisted copper pairs are sheathed
directly in a plastic covering without a foil shield. This is
the simplest and cheapest form of indoor telephone and data
network cabling. |
| Section
V |
| valid
cell, packet or frame A cell in which the header is
declared by the header error control process to be free of errors.
|
| virtual
connection A means of conveying data from origin to
destination without there ever being a dedicated physical path
between the two. An example is a packet-switched connection.
|
| VLAN
(virtual-bridged LAN) A means by which LAN users on
different physical segments can be interconnected as if they
were part of a single broadcast domain. |
| VOIP
(voice over IP) The practice of communicating live
telephone conversation or audio conferencing signals in real-time
by means of the Internet protocol (IP) or the Internet itself.
|
| VPN
(virtual private network) As far as the user of a VPN
is concerned, the network appears to be a private network---with
the security and network performance benefits of a dedicated
network---but is actually carried by means of a public network
(e.g. the Internet). The result is a virtual private network
achieved at lower cost. |
| Section
W |
| (WAN)
wide area network A term applied to describe the long
distance part of a network. |
| web
browser A software used by human users to `surf' the
Internet and view documents held in html format. |
| webpage
An html document held somewhere in the Worldwide Web. When viewed
using a web browser, the page appears like a page of text, maybe
including pictures and (underlined) hyperlinks which provide
for quick connection to other related web pages. |
| web
server A computer and associated software connected
to the Internet on which the web pages related to a given domain
(e.g. all those of www.company.com) are stored. The server responds
to requests from Internet `surfers' by means of http. |
| website
Any machine connected to the Internet running a web server.
|
| Worldwide
Web (www) An interconnected network of computer servers
around the world, which provide for fast and easy access to
online information via the Internet. |
