Abbreviations and Technical Terms
79
UDP
Stands for
U
ser
D
atagram
P
rotocol and can be used instead of
Æ
TCP if
reliability is not an issue. UDP does not guarantee that packets will be de-
livered, nor does it ensure that packets will arrive in a certain order.
URI
Abbreviation of
U
niform
R
esource
I
dentifier. Content is identified in the In-
ternet with a URI. In general, content refers to files of all possible format,
for example text, HTML, XML, video, sound to name but a few. The most
frequent form of URI is a URL. A typical URI describes:
•
the mechanism for accessing the content (for example a protocol, such
as http, ftp or file)
•
the computer on which the content is located
•
the specific name of the content on this computer (usually a file name)
The parts are optional which is why a file name is a (relative) URI.
URL
Abbreviation of
U
niform
R
esource
L
ocator. A URL is the address of a file
that can be accessed over the Internet. The type of file is defined by the
access protocol (not the file type). For example, the HTTP protocol sup-
ports HTML pages, Java applets, CGI scripts, etc. A URL consists of
•
the access protocol
•
a computer name (the domain)
•
a specific file name
VLAN
Abbreviation of "
V
irtual
L
ocal
A
rea
N
etwork."
The division of an
Æ
IP network into autonomous administration groups
(domains). One way of indicating association with a VLAN is to use a
Æ
VLAN ID.
VLAN is therefore a network structure with all the properties of a conven-
tional LAN, but without a physical connection. The distance between sta-
tions in a LAN is limited; a VLAN, on the other hand, lets you connect even
more remote nodes to a virtual local network.
VLAN ID
With switches, VLAN divisions can exceed switch boundaries. A special
mechanism is provided for this. It allows you to send packets between the
switches and identifies them as belonging to a specific VLAN. Every VLAN
is assigned a specific VLAN ID (VID) for this.
