Glossary - X
Prefix used by the CCITT to identify standards concerning data
networks. See also X.25, X.400, X.500.
A ITU-TSS packet switching
network address standard. See X.25, NSAP,
One of the first - CCITT standardized - public (data)
packet switching network protocols. Originally
designed to operate over unreliable communications links, it supported both virtual circuit
(VC) and datagram
services. It specifies the protocols and functions of layers 1, 2 and 3 at the interface between
users and the network for this type of network. See X.121.
- X.400 (standard, messaging)
The international standard protocol for electronic mail.
X.400 defines an electronic system for exchanging messages among store-and-forward mail systems.
- X.500 (standard, communications)
The ITU-T and ISO international
standard for electronic directory services that store and serve (to clients using a variety of
interfaces) centrally-managed personal location information. The standard defines a hierarchical
directory structure for administrative domains (organization, divisions, departments and workgroups).
Examples: white pages, Knowbot,
- X.509 (standard, communications)
A security standard that defines a certification process by which users are authenticated.
- Cross-Connect (network)
Xrm Decrease Factor (ATM)
An ABR service parameter, XDF controls the decrease in ACR associated
with Xrm. It is a power of two in range: [0, 1].
eXternal Data Representation
A standard for machine independent data structures developed by Sun Microsystems and defined
in RFCs 1014 and 1832. It is similar to
Abstract Syntax Notation One (ASN.1) [Source: RFC1208].
eXtensible Markup Language (language, text, Internet)
An initiative from the W3C defining an "extremely simple" dialect
of SGML suitable for use on the World-Wide Web.
Web site: http://www.w3.org/XML/.
- eXtended Memory Specification (hardware)
Xerox Network Systems (network)
A protocol suite developed by Xerox Corporation to run on LAN
and WAN networks, where the LANs are typically
Ethernet. Implementations exist for both Xerox's workstations
and 4.3BSD, and 4.3BSD-derived, systems.
XNS denotes not only the protocol stack, but also an architecture of standard programming interfaces,
conventions, and service functions for authentication, directory, filing, email, and remote
XNS is also the name of Xerox's implementation.
An ABR service parameter, Xrm limits the number of forward RM-cells
which may be sent in the absence of received backward RM-cells. The range is 0-255.
- eXpress Transport Protocol (network)
- X-Windows (standard)
X is the name for TCP/IP based network-oriented window systems.
Network window systems allow a program to use a display on a different computer.
The most widely-implemented window system is X11 - a component of MIT's Project Athena.