Glossary O
Centillion 1200N ATM Switch User Manual B-53
NTP 297-8103-903
OSC
Oscillator: A device for generating an analog test signal or a n electronic circuit that
creates a single frequency signal.
OSI
Open Systems Interconnection: 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 Physical Layer
Usually taken to be SONET/SDH (which itself has 4 layers...) but can be other
things as well. The PHY deals with medium-related issues.1
OSPF
Open Shortest Path First: A link-state routing algorithm that is used to calculate
routes based on the number of routers, transmission speed, delays and route cost.
OUI
Organizationally Unique Identifier: The OUI is a three-octet field in the IEEE
802.1a defined SubNetwork Attachment Point (SNAP) header, identifying an
organization which administers the meaning of the following two octet Protocol
Identifier (PID) field in the SNAP header. Together the y identify a distinct routed
or bridged protocol.
Outlier
A node whose exclusion from its containing peer group would significantly
improve the accuracy and simplicity of the aggregation of the remain der of the peer
group topology.
Outside Link
A link to an outside node.
Outside Node
A node which is participating in PNNI routing, but which is not a member of a
particular peer group.
1.ICell Relay Retreat. Indiana University 25 August 1996
http://cell-relay.indiana.edu/cell-relay/