Technical data

© 2012 Meru Networks, Inc. Glossary 329
CSMA-CA
CSMA/CA is the principle medium access method employed by IEEE 802.11 WLANs. It is a
"listen before talk" method of minimizing (but not eliminating) collisions caused by simul-
taneous transmission by multiple radios. IEEE 802.11 states collision avoidance method
rather than collision detection must be used, because the standard employs half duplex
radios-radios capable of transmission or reception-but not both simultaneously.
CSMA/CD
A method of managing traffic and reducing noise 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.
D
dBm
A measurement of relative power (decibel) related to 1 milliwatt (mW).
Denial of Service
(DoS) A condition in which users are deliberately prevented from using network resources.
DES
Data Encryption Standard. A symmetric encryption algorithm that always uses 56 bit keys.
It is rapidly being replaced by its more secure successor, 3DES.
DHCP
A utility that enables a server to dynamically assign IP addresses from a predefined list for
a predefined time period, limiting their use time so that they can be reassigned. Without
DHCP, IP addresses would have to be manually assigned to all computers on the network.
When DHCP is used, whenever a computer logs onto the network, it automatically is
assigned an IP address.
DNS
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 myweb-
site.com to a series of numbers like 107.22.55.26. Every website has its own specific IP
address on the Internet.
DSL
Various technology protocols for high-speed data, voice and video transmission over ordi-
nary twisted-pair copper POTS (Plain Old Telephone Service) telephone wires.
E
EAP
Extensible Authentication Protocol. An extension to PPP. EAP is a general protocol for
authentication that also supports multiple authentication methods, such as token cards,
Kerberos, one-time passwords, certificates, public key authentication and smart cards.
IEEE 802.1x specifies how EAP should be encapsulated in LAN frames.
EAP-TLS
Extensible Authentication Protocol with Transport Layer Security. EAP-TLS supports mutual
authentication using digital certificates. When a client requests access, the authentication
server responds with a server certificate. The client replies with its own certificate and
also validates the server certificate. The certificate values are used to derive session
encryption keys.