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Professional Access Point
Administrator Guide
Glossary - 308
D
DCF
The Distribution Control Function is a component of the IEEE 802.11e Quality of Service (QoS) technology
standard. The DCF coordinates channel access among multiple stations on a wireless network by
controlling wait times for channel access. Wait times are determined by a random backoff timer which is
configurable by defining minimum and maximum contention windows. See also EDCF.
DHCP
The Dynamic Host Configuration Protocol (DHCP) is a protocol specifying how a central server can
dynamically provide network configuration information to clients. A DHCP server offers a lease (for a pre-
configured period of time—see Lease Time) to the client system. The information supplied includes the
client's IP addresses and netmask plus the address of its DNS servers and Gateway.
DNS
The Domain Name Service (DNS) is a general-purpose query service used for translating fully-qualified
names into Internet addresses. A fully-qualified name consists of the hostname of a system plus its domain
name. For example,
www
is the host name of a Web server and
www.usr.com
is the fully-qualified name of
that server. DNS translates the domain name
www.usr.com
to an IP address, for example
66.93.138.219
.
A domain name identifies one or more IP addresses. Conversely, an IP address may map to more than
one domain name.
A domain name has a suffix that indicates which top level domain (TLD) it belongs to. Every country has its
own top-level domain, for example
.de
for Germany,
.fr
for France,
.jp
for Japan,
.tw
for Taiwan,
.uk
for
the United Kingdom,
.us
for the U.S.A., and so on. There are also
.com
for commercial bodies,
.edu
for
educational institutions,
.net
for network operators, and
.org
for other organizations as well as
.gov
for
the U. S. government and
.mil
for its armed services.
DOM
The Document Object Model (DOM) is an interface that allows programs and scripts to dynamically access
and update the content, structure, and style of documents. The DOM allows you to model the objects in an
HTML or XML document (text, links, , tables), defining the attributes of each object and how they can be
manipulated.
Further details about the DOM can be found at the W3C.
DTIM
The Delivery Traffic Information Map (DTIM) message is an element included in some Beacon frames. It
indicates which stations, currently sleeping in low-power mode, have data buffered on the Access Point
awaiting pick-up. Part of the DTIM message indicates how frequently stations must check for buffered
data.
Dynamic IP Address
See IP Address.