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Glossary
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SYN Flood. A method that the user of a hostile client program can use to conduct a denial-of-service (DOS)
attack on a computer server. The hostile client repeatedly sends SYN (synchronization) packets to every
port on the server, using fake IP addresses.
T
TCP/IP (Transmission Control Protocol/Internet Protocol). A method of packet-switched data
transmission used on the Internet. The protocol specifies the manner in which a signal is divided into parts,
as well as the manner in which “address” information is added to each packet to ensure that it reaches its
destination and can be reassembled into the original message.
Transmission Control Protocol/Internet Protocol (TCP/IP). See TCP/IP.
U
UDP (User Datagram Protocol). A TCP/IP protocol describing how data packets reach application programs
within a destination computer.
V
VPI (Virtual Path Identifier). Identifier contained in the ATM cell header to designate the virtual path on the
physical ATM link.
VCI (Virtual Channel Identifier). Identifier contained in the ATM cell header to designate the virtual channel
on the physical ATM link.
W
Wireless. Transmission of data over radio waves rather than wiring.
Wireless channel. The 2Wire gateway supports up to 13 wireless channels (based on country restrictions).
For example, the United States and Canada support channels 1 to 11; Europe and Australia support
channels 1 to 13.
In an 802.1b or 802.11g wireless network, data is transmitted at 2.5GHz. Wireless nodes communicate
with each other using radio frequency signals in the band between 2.4GHz and 2.5GHz. Neighboring
channels are 5 MHz apart; however, due to the spread spectrum effect of the signals, a node sending
signals using a particular channel will use frequency spectrum 12.5HHz above and below the center
channel frequency. As a result, two separate wireless networks using neighboring channels (for example,
channels 1 and 2) in the same general vicinity will interfere with each other. Applying two channels that
allow the maximum channel separation (such as channels 1 and 6, or channels 6 and 11) will provide a
noticeable performance increase over networks with minimal channel separation.
The radio frequency channels used in 802.11b/g networks are shown in the following table.
Channel Range
Channel 1 2399.5 MHz - 2424.5 MHz
Channel 2 2404.5 MHz - 2429.5 MHz