3130
Bit - A binary digit. The value - 0 or 1-used in the binary numbering system.
Also, the smallest form of data.
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) - In local
area networking, this is the CSMA technique that combines slotted time-divi-
sion multiplexing with carrier sense multiple access/collision detection
(CSMA/CD) to avoid having collisions occur a second time. This works best if
the time allocated is short compared to packet length and if the number of sit-
uations is small.
CSMA/CD (Carrier Sense Multiple Access/Collision Detection) - The LAN
access method used in Ethernet. When a device wants to gain access to the net-
work, it checks to see if the network is quiet (senses the carrier). If it is not, it
waits a random amount of time before retrying. If the network is quiet and two
devices access the line at exactly the same time, their signals collide. When the
collision is detected, they both back off and each wait a random amount of time
before retrying.
CTS(Clear To Send) - An RS-232 signal sent from the receiving station to the
transmitting station that indicates it is ready to accept data.
Default Gateway - The routing device used to forward all traffic that is not
addressed to a station within the local subnet.
DHCP (Dynamic Host Configuration Protocol) - A protocol that lets network
administrators manage centrally and automate the assignment of Internet
Protocol (IP) addresses in an organization's network. Using the Internet's set of
protocol (TCP/IP), each machine that can connect to the Internet needs a
unique IP address. When an organization sets up its computer users with a con-
nection to the Internet, an IP address must be assigned to each machine.
Without DHCP, the IP address must be entered manually at each computer and,
if computers move to another location in another part of the network, a new IP
address must be entered. DHCP lets a network administrator supervise and dis-
tribute IP addresses from a central point and automatically sends a new IP
address when a computer is plugged into a different place in the network.
DHCP uses the concept of a "lease" or amount of time that a given IP address
will be valid for a computer. The lease time can vary depending on how long a
user is likely to require the Internet connection at a particular location. It's espe-
cially useful in education and other environments where users change fre-
quently. Using very short leases, DHCP can dynamically reconfigure networks
in which there are more computers than there are available IP addresses.
Appendix B: Glossary
802.11b - One of the IEEE standards for wireless networking hardware.
Products that adhere to a specific IEEE standard will work with each other,
even if they are manufactured by different companies. The 802.11b standard
specifies a maximum data transfer rate of 11Mbps, an operating frequency of
2.4GHz, and WEP encryption for security. 802.11b networks are also referred
to as Wi-Fi networks.
802.11g - A proposed, but as yet unratified extension of the IEEE 802.11 stan-
dard for wireless networking hardware. The draft 802.11g specifications used
by Linksys specify a maximum data transfer rate of 54Mbps using OFDM
modulation, an operating frequency of 2.4GHz, backward compatibility with
IEEE 802.11b devices, and WEP encryption for security.
Adapter - Printed circuit board that plugs into a PC to add to capabilities or
connectivity to a PC. In a networked environment, a network interface card is
the typical adapter that allows the PC or server to connect to the intranet and/or
Internet.
Ad-hoc Network - An ad-hoc network is a group of computers, each with a
wireless adapter, connected as an independent 802.11 wireless LAN. Ad-hoc
wireless computers operate on a peer-to-peer basis, communicating directly
with each other without the use of an access point. Ad-hoc mode is also
referred to as an Independent Basic Service Set or as peer-to-peer mode.
Automatic Fall-back - A feature provided by some wireless products to
increase connection reliability. Automatic fall-back enables a device to dynam-
ically shift between various data transfer rates. It works by decreasing the data
transfer rate when interference increases, distance increases, and other factors
undermine signal strength and quality.
Backbone - The part of a network that connects most of the systems and net-
works together and handles the most data.
Bandwidth - The transmission capacity of a given facility, in terms of how
much data the facility can transmit in a fixed amount of time; expressed in bits
per second (bps).