NETGEAR 7200 Series User Manual page 144

User Manual for the NETGEAR 7200 Series Layer 2 Managed Switch Software
them, and are the only areas that can contain an ASBR. Compare with stub area. See also ASAM and OSPF.
(Cisco Systems Inc.)
O
Open Systems Interconnection
OSI is a seven (7) layer architecture model for communications systems developed by the ISO for the
interconnection of data communications systems. Each layer uses and builds on the services provided by
those below it.
OSI
See "Open Systems Interconnection" on page 12.
P
packet
A block of information sent over a network. A packet typically contains a source and destination network
address, some protocol and length information, a block of data, and a checksum.
PDU
See "Protocol Data Unit" on page 13.
PHY
The OSI Physical Layer: The physical layer provides for transmission of cells over a physical medium
connecting two ATM devices. This physical layer is comprised of two sublayers: the Physical Medium
Dependent (PMD) sublayer, and the Transmission Convergence (TC) sublayer.
PMC
Packet Mode Channel.
Point-to-Point Protocol
PPP. A protocol allowing a computer using TCP/IP to connect directly to the Internet.
Port Mirroring
Also known as a roving analysis port. This is a method of monitoring network traffic that forwards a copy of
each incoming and outgoing packet from one port of a network switch to another port where the packet can
be studied. A network administrator uses port mirroring as a diagnostic tool or debugging feature, especially
when fending off an attack. It enables the administrator to keep close track of switch performance and alter it
if necessary. Port mirroring can be managed locally or remotely. An administrator configures port mirroring
by assigning a port from which to copy all packets and another port where those packets will be sent. A
B-12 Glossary
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