Jun 26, 2010

Wireless Network Glossary-Part2

Adhoc
A Peer-to-Peer wireless network. An Adhoc wireless network do not use wireless AP or
router as the central hub of the network. Instead, wireless client are connected directly to
each other. The disadvantage of Adhoc network is the lack of wired interface to Internet
connections. It is not recommended for network more than 2 nodes.


Access Point (AP)
The central hub of a wireless LAN network. Access Points have one or more Ethernet
ports that can connect devices (such as Internet connection) for sharing. Multi-function
Access Point can also function as an Ethernet client, wireless bridge, or repeat signals from
other AP. Access Points typically have more wireless functions comparing to wireless
routers.


ACK Timeout
Acknowledgement Timeout Windows. When a packet is sent out from one wireless station
to the other, it will waits for an Acknowledgement frame from the remote station. The
station will only wait for a certain amount of time, this time is called the ACK timeout. If the
ACK is NOT received within that timeout period then the packet will be re-transmitted
resulting in reduced throughput. If the ACK setting is too high then throughput will be lost


due to waiting for the Ack Window to timeout on lost packets. If the ACK setting is too low
then the ACK window will have expired and the returning packet will be dropped, greatly
lowering throughput. By having the ability to adjust the ACK setting we can effectively
optimize the throughput over long distance links. This is especially true for 802.11a and
802.11g networks. Setting the correct ACK timeout value need to consider 3 factors:
distance, AP response time, and interference. The Air3G provide ACK adjustment
capability in form of either distance or direct input. When you enter the distance
parameter, the Air3G will automatically calculate the correct ACK timeout value.


Bandwidth Management (Traffic Control)
Bandwidth Management controls the transmission speed of a port, user, IP address, and
application. Router can use bandwidth control to limit the Internet connection speed of
individual IP or Application. It can also guarantee the speed of certain special application
or privileged IP address - a crucial feature of QoS (Quality of Service) function.


Bootloader
Bootloader is the under layering program that will start at the power-up before the device
loads firmware. It is similar to BIOS on a personal computer. When a firmware crashed,
you might be able to recover your device from bootloader.


Bridge
A product that connects 2 different networks that uses the same protocol. Wireless
bridges are commonly used to link network across remote buildings. For wireless
application, there are 2 types of Bridges. WDS Bridge can be used in Point-to-Point or
Point-to-Multipoint topology. Bridge Infrastructure works with AP mode to form a star
topology.



Cable and Connector Loss: During wireless design and deployment, it is important to
factor in the cable and connector loss. Cable and connector loss will reduce the output
power and receiver sensitivity of the radio at connector end. The longer the cable length is,
the more the cable loss. Cable loss should be subtracted from the total output power
during distance calculation. For example, if the cable and connector loss is 3dBm and the
output power is 20dBm; the output power at the cable end is only 17dBm.



Client
Client means a network device or utility that receives service from host or server. A client device means end user device such as wireless cards or wireless CPE.



CPE Devices
CPE stands for Customer Premises Equipment. A CPE is a device installed on the end
user's side to receive network services. For example, on an ADSL network, the ADSL
modem/router on the subscriber's home is the CPE device. Wireless CPE means a
complete Wireless (usually an AP with built-in Antenna) that receive wireless broadband
access from the WISP. The opposite of CPE is CO.


CTS
Clear To Send. A signal sent by a device to indicate that it is ready to receive data.


DDNS
Dynamic Domain Name System. An algorithm that allows the use of dynamic IP address
for hosting Internet Server. A DDNS service provides each user account with a domain
name. A router with DDNS capability has a built-in DDNS client that updates the IP
address information to DDNS service provider whenever there is a change. Therefore,
users can build website or other Internet servers even if they don't have fixed IP connection.


DHCP
Dynamic Hosting Configuration Protocol. A protocol that enables a server to dynamically
assign IP addresses. When DHCP is used, whenever a computer logs onto the network, it automatically gets an IP address assigned to it by DHCP server. A DHCP server can either be a designated PC on the network or another network device, such as a router.


DMZ
Demilitarized Zone. When a router opens a DMZ port to an internal network device, it opens
all the TCP/UDP service ports to this particular device. The feature is used commonly for
setting up H.323 VoIP or Multi-Media servers.

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