Hirschmann RS20 Reference Manual page 222

Glossary
W
WAN. See "Wide Area Network" on
page 222.
Web. Also known as World-Wide
Web (WWW) or W3. An Internet
client-server system to distribute
information, based upon the
hypertext transfer protocol (HTTP).
Wide Area Network. A WAN is a
computer network that spans a
relatively large geographical area.
Typically, a WAN consists of two or
more local-area networks (LANs).
X
X.500. A directory standard that
enables applications like e-mail to
access information that can either
be central or distributed. The benefit
of a directory is the ability to
minimize the impact on the user of
changes to a network. The standard
is broken down under subsequent
standards, as follows:
X.501 Models
X.509 Authentication framework
X.511 Abstract service definition
X.518 Procedures for distributed
operation
X.519 Protocol specifications
X.520 Selected attribute types
X.521 Selected object types
222
XModem. One of the most popular
file transfer protocols (FTPs).
Xmodem is fairly effective at
detecting errors. It sends blocks of
data together with a checksum and
then waits for acknowledgment of
the block's receipt. The waiting
slows down the rate of data
transmission considerably, but it
ensures accurate transmission.
Xmodem can be implemented either
in software or in hardware. Many
modems, and almost all
communications software packages,
support Xmodem. However, it is
useful only at relatively slow data
transmission speeds (less than
4,800 bps). Enhanced versions of
Xmodem that work at higher
transmission speeds are known as
Ymodem and Zmodem.
CLI L2B
Release 4.0 11/07