CCNA Cisco Certified Network Associate Study Guide - FTP Server

Glossary 695
OSI reference model Open System Interconnection reference model: A
conceptual model defined by the International Organization for Standardization
(ISO), describing how any combination of devices can be connected
for the purpose of communication. The OSI model divides the task into
seven functional layers, forming a hierarchy with the applications at the top
and the physical medium at the bottom, and it defines the functions each
layer must provide. See also: Application layer, Data Link layer, Network
layer, Physical layer, Presentation layer, Session layer, and Transport layer.
OSPF Open Shortest Path First: A link-state, hierarchical IGP routing algorithm
derived from an earlier version of the IS-IS protocol, whose features
include multipath routing, load balancing, and least-cost routing. OSPF is
the suggested successor to RIP in the Internet environment. See also:
Enhanced IGRP, IGP, and IP.
OUI Organizationally Unique Identifier: Is assigned by the IEEE to an
organization that makes network interface cards. The organization then puts
this OUI on each and every card they manufacture. The OUI is 3 bytes
(24 bits) long. The manufacturer then adds a 3-byte identifier to uniquely
identify the host on an internetwork. The total length of the address is 48 bits
(6 bytes) and is called a hardware address or MAC address.
out-of-band management Management “outside” of the network’s
physical channels. For example, using a console connection not directly
interfaced through the local LAN or WAN or a dial-in modem. Compare to:
in-band management.
out-of-band signaling Within a network, any transmission that uses
physical channels or frequencies separate from those ordinarily used for data
transfer. For example, the initial configuration of a Cisco Catalyst switch
requires an out-of-band connection via a console port.
packet In data communications, the basic logical unit of information
transferred. A packet consists of a certain number of data bytes, wrapped or
encapsulated in headers and/or trailers that contain information about
where the packet came from, where it’s going, and so on. The various protocols
involved in sending a transmission add their own layers of header
information, which the corresponding protocols in receiving devices then
interpret.