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Domain
- A subnetwork comprised of a group of clients and servers under the control of
one security database. Dividing LANs into domains improves performance and security.
Download
- To receive a file transmitted over a network. In a communications session,
download means receive, and upload means transmit.
DSL -
(Digital Subscriber Line) - An always-on broadband connection over traditional
phone lines.
Driver
- A workstation or server software module that provides an interface between a
network interface card and the upper-layer protocol software running in the computer; it
is designed for a specific NIC, and is installed during the initial installation of a network-
compatible client or server operating system.
DSSS (Direct-Sequence Spread-Spectrum)
- DSSS generates a redundant bit pattern
for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The
longer the chip, the greater the probability that the original data can be recovered. Even
if one or more bits in the chip are damaged during transmission, statistical techniques
embedded in the radio can recover the original data without the need for retransmission.
To an unintended receiver, DSSS appears as low power wideband noise and is rejected
(ignored) by most narrowband receivers.
DTIM -
(Delivery Traffic Indication Message) - A message included in data packets that
can increase wireless efficiency.
Dynamic IP Address
- An IP address that is automatically assigned to a client station in
a TCP/IP network, typically by a DHCP server. Network devices that serve multiple
users, such as servers and printers, are usually assigned static IP addresses.
Dynamic Routing
- The ability for a router to forward data via a different route based on
the current conditions of the communications circuits. For example, it can adjust for
overloaded traffic or failing lines and is much more flexible than static routing, which
uses a fixed forwarding path.
Encapsulation
- The wrapping of data in a particular protocol header. For example,
Ethernet data is wrapped in a specific Ethernet header before network transit.
Encryption
- Applying a specific algorithm to data in order to alter the data’s
appearance and prevent other devices from reading information. Decryption applies the
algorithm in reverse to restore the data to its original form.
Ethernet
- A baseband LAN specification invented by Xerox Corporation and developed
jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks operate at
10 Mbps using CSMA/CD to run over coaxial cable. Ethernet is similar to a series of
standards produced by IEEE referred to as IEEE 802.3.
Fast Ethernet
- A 100 Mbps technology based on the 10Base-T Ethernet CSMA/CD
network access method.
Firewall
- A firewall is a set of related programs, located at a network gateway server,
which protects the resources of a network from users from other networks. (The term
also implies the security policy that is used with the programs.) An enterprise with an
intranet that allows its workers access to the wider Internet installs a firewall to prevent
outsiders from accessing its own private data resources and for controlling what outside
resources to which its own users have access. Basically, a firewall, working closely with
a router, examines each network packet to determine whether to forward it toward its
destination.
Firmware
- Programming that is inserted into programmable read-only memory, thus
becoming a permanent part of a computing device.
