User's Manual
143
www.gateway.com
Multicast
A Multicast sends the same message to a select group of recipients. Sending an e-mail
message to a mailing list is an example of multicasting. In wireless networks, multicast
usually refers to an interaction in which the access point sends data traffic in the form of
IEEE 802.1x Frames to a specified set of client stations (MAC addresses) on the network.
Some wireless security modes distinguish between how unicast, multicast, and broadcast
frames are encrypted or whether they are encrypted.
See also
Unicast and Broadcast.
NAT
Network Address Translation is an Internet standard that masks the internal IP addresses
being used in a
LAN. A NAT server running on a gateway maintains a translation table
that maps all internal IP addresses in outbound requests to its own address and converts
all inbound requests to the correct internal host.
NAT serves three main purposes: it provides security by obscurity by hiding internal IP
addresses, enables the use of a wide range of internal IP addresses without fear of conflict
with the addresses used by other organizations, and it allows the use of a single Internet
connection.
Network Address
See
IP Address.
NIC
A Network Interface Card is an adapter or expansion board inserted into a computer to
provide a physical connection to a network. Most NICs are designed for a particular type
of network, protocol, and media, for example,
Ethernet or wireless.
NTP
The Network Time Protocol assures accurate synchronization of the system clocks in a
network of computers. NTP servers transmit Coordinated Universal Time (UTC, also known
as Greenwich Mean Time) to their client systems. An NTP client sends periodic time requests
to servers, using the returned time stamp to adjust its clock.
OSI
The Open Systems Interconnection (OSI) reference model is a framework for network design.
The OSI model consists of seven layers:
■ Layer 1, the Physical layer, identifies the physical medium used for communication
between nodes.
■ In the case of wireless networks, the physical medium is air, and radio frequency (RF)
waves are a components of the physical layer.