User manual

100 www.cooperbussmann.com/wirelessresources
Cooper Bussmann 245U-E Wireless Ethernet Modem & Device Server User Manual
Rev Version 2.19
appENDIx B - GLOSSarY
ACK
Message acknowledgment.
Access Point
An access point connects wireless network stations (or clients) to other stations within the
wireless network and also can serve as the point of interconnection between the wireless
network and a wired network. Each access point can serve multiple users within a defined
network area. Also known as a base station.
Ad-Hoc Network
Ad hoc network often refers to a mode of operation of IEEE 802.11 wireless networks. An
ad hoc network is any set of networks where all devices have equal status on a network
and are free to associate with any other ad hoc network device in link range. Each node
participates in routing by forwarding data for other nodes, so the determination of which
nodes forward data is made dynamically on the basis of network connectivity.
Antenna Gain
Antennae do not increase the transmission power, but instead focus the signal. Rather
than transmitting in every direction (including the sky and ground), antenna focus the signal
more horizontally or in one particular direction. This gain is measured in decibels.
Bandwidth
The maximum data transfer speed available to a user through a network.
Bridge
A bridge connects two local area networks, and is typically used to connect wireless
networks to wired networks. Bridges usually transfer messages between networks only
when the message destination is on the other network. Messages destined for the network
on which they originated are not passed on to the other network. This reduces traffic on the
entire network.
Collision Avoidance
A network node procedure for proactively detecting that it can transmit a signal without
risking a collision with transmissions from other network nodes.
Client / Sta / Station
A device on a network that gains access to data, information, and other devices through a
server (access point).
Crossover Cable
A cable used for networking two computers without the use of a hub. Crossover cables
may also be required for connecting a cable or DSL modem to a wireless gateway or
access point. The cable is wired so that the signals “crossover,” connecting transmit signal
on one side to receiver signals on the other.
CSMA/CA
Carrier sense multiple access/collision avoidance (CSMA/CA) is a “listen before talk”
method of minimizing (but not eliminating) collisions caused by simultaneous transmission
by multiple radios. IEEE 802.11 states that a collision avoidance method rather than
collision detection must be used because the standard employs half-duplex radios, which
are capable of transmission or reception but not both simultaneously.
Unlike conventional wired Ethernet nodes, a WLAN station cannot detect a collision while
transmitting. If a collision occurs, the transmitting station will not receive an ACKnowledge
packet from the intended receive station. For this reason, ACK packets have a higher
priority than all other network traffic. After completion of a data transmission, the receive
station will begin transmission of the ACK packet before any other node can begin
transmitting a new data packet. All other stations must wait a longer pseudo-randomized
period of time before transmitting. If an ACK packet is not received, the transmitting station
will wait for a subsequent opportunity to retry the transmission.
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).