Extreme Networks Summit WM User Manual page 315

Term
NTP
OFDM
OID
OPSEC
OS
OSI
OSI Layer 2
OSI Layer 3
Summit WM User Guide, Software Version 5.3
Explanation
Network Time Protocol, an Internet standard protocol (built on top of
TCP/IP) that assures accurate synchronization to the millisecond of
computer clock times in a network of computers. Based on UTC, NTP
synchronizes client workstation clocks to the U.S. Naval Observatory
Master Clocks in Washington, DC and Colorado Springs CO. Running as a
continuous background client program on a computer, NTP sends periodic
time requests to servers, obtaining server time stamps and using them to
adjust the client's clock. (RFC1305)
Orthogonal frequency division multiplexing, a method of digital
modulation in which a signal is split into several narrowband channels at
different frequencies. OFDM is similar to conventional frequency division
multiplexing (FDM). The difference lies in the way in which the signals are
modulated and demodulated. Priority is given to minimizing the
interference, or crosstalk, among the channels and symbols comprising the
data stream. Less importance is placed on perfecting individual channels.
OFDM is used in European digital audio broadcast services. It is also used
in wireless local area networks.
Object Identifier.
OPSEC (Open Platform for Security) is a security alliance program created
by Check Point to enable an open industry-wide framework for
interoperability of security products and applications. Products carrying
the "Secured by Check Point" seal have been tested to guarantee integration
and interoperability.
Operating system.
Open System Interconnection. An ISO standard for worldwide
communications that defines a networking framework for implementing
protocols in seven layers. Control is passed from one layer to the next,
starting at the application layer in one station, down through the
presentation, session, transport, network, data link layer to the physical
layer at the bottom, over the channel to the next station and back up the
hierarchy.
At the Data Link layer (OSI Layer 2), data packets are encoded and
decoded into bits. The data link layer has two sublayers:
The Logical Link Control (LLC) layer controls frame synchronization,
flow control and error checking
The Media Access Control (MAC) layer controls how a computer on the
network gains access to the data and permission to transmit it.
The Network layer (OSI Layer 3) provides switching and routing
technologies, creating logical paths, known as virtual circuits, for
transmitting data from node to node. Routing and forwarding are functions
of this layer, as well as addressing, internetworking, error handling,
congestion control and packet sequencing.
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