
Glossary
SCALANCE WLC711
A-8 C79000-G8976-C260-03, 07/2012, User Guide, V8.11
OFDM 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.
OID Object Identifier.
OS Operating system.
OSI 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.
OSI Layer 2 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.
OSI Layer 3 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.
OSPF Open Shortest Path First, an interior gateway routing protocol developed for IP networks
based on the shortest path first or link-state algorithm. Routers use link-state algorithms to
send routing information to all nodes in an internetwork by calculating the shortest path to
each node based on a topography of the Internet constructed by each node. Each router
sends that portion of the routing table (keeps track of routes to particular network
destinations) that describes the state of its own links, and it also sends the complete routing
structure (topography). Using OSPF, a host that obtains a change to a routing table or
detects a change in the network immediately multicasts the information to all other hosts in
the network so that all will have the same routing table information. The host using OSPF
sends only the part that has changed, and only when a change has taken place. (RFC2328)
OUI Organizationally Unique Identifier (used in MAC addressing).
Packet The unit of data that is routed between an origin and a destination on the Internet or any
other packet-switched network. When any file is sent from one place to another on the
Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file into
packets. Each packet is separately numbered and includes the Internet address of the
destination. The individual packets for a given file may travel different routes through the
Internet. When they have all arrived, they are reassembled into the original file (by the TCP
layer at the receiving end).
PAP Password Authentication Protocol is the most basic form of authentication, in which a user's
name and password are transmitted over a network and compared to a table of name-
password pairs. Typically, the passwords stored in the table are encrypted. (See CHAP).
Table A-1 Networking Terms and Abbreviations (continued)
Term Explanation
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