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245U-E Wireless Ethernet Modem User Manual
115
Rev Version 2.24
CSMA/CD
Carrier sense multiple access/collision detection (CSMA/CD) is the access method
used on an Ethernet network. A network device transmits data after detecting that
a channel is available. However, if two devices transmit data simultaneously, the
sending devices detect a collision and retransmit after a random time delay.
DHCP
Dynamic Host Configuration Protocol (DHCP) is a utility that enables a server to
dynamically assign IP addresses from a predefined list and limit their time of use so
that they can be reassigned. Without DHCP, an IT manager would need to manually
enter all the IP addresses of all the computers on the network. When DHCP is
used, whenever a computer logs onto the network, an IP address is automatically
assigned to it.
Dial-up
A communication connection via the standard telephone network, or plain old
telephone service (POTS).
DNS
Domain name service (DNS) is a program that translates URLs to IP addresses by
accessing a database maintained on a collection of Internet servers. The program
works behind the scenes to facilitate surfing the Web with alpha versus numeric
addresses. A DNS server converts a name like mywebsite.com to a series of
numbers like 107.22.55.26. Every website has its own specific IP address on the
Internet.
DSL
Digital subscriber line (DSL) is a family of technology protocols for high-speed data,
voice and video transmission over ordinary twisted-pair copper plain old telephone
service (POTS) telephone wires.
Encryption Key
An alphanumeric (letters and/or numbers) series that enables data to be encrypted
and then decrypted so it can be safely shared among members of a network. WEP
uses an encryption key that automatically encrypts outgoing wireless data. On the
receiving side, the same encryption key enables the computer to automatically
decrypt the information so that it can be read. Encryption keys should be kept
secret.
Firewall
A device or computer program that keeps unauthorized users out of a private
network. Everything entering or leaving a system’s internal network passes
through the firewall and must meet the system’s security standards in order to
be transmitted. Often used to keep unauthorized people from using systems
connected to the Internet.
Hub
A multiport device used to connect PCs to a network via Ethernet cabling or via
802.11. Wired hubs can have numerous ports and can transmit data at speeds
ranging from 10 Mbps to multi-Gigabyte speeds per second. A hub transmits
packets it receives to all the connected ports. A small wired hub may only connect
4 computers; a large hub can connect 48 or more.
Hz
Hertz. The international unit for measuring frequency, equivalent to the older unit
of cycles-per-second. One megahertz (MHz) is one million hertz. One gigahertz
(GHz) is one billion hertz. The standard US electrical power frequency is 60 Hz,
the AM broadcast radio frequency band is 535–605 kHz, the FM broadcast radio
frequency band is 88–108 MHz, and wireless 802.11b/g LANs operate at 2.4 GHz.
IEEE
Institute of Electrical and Electronics Engineers, New York, www.ieee.org. A
membership organization that includes engineers, scientists and students in
electronics and allied fields. IEEE has more than 300,000 members and is involved
with setting standards for computers and communications.
