Glossary - O

OAM

Operation, Administration, and Maintenance (ATM)
A range of diverse network management functions performedby dedicated ATM cells, including fault and performance management (operations); addressing, data collection, and usage monitoring (administration); and analysis, diagnosis, and repair of network faults (maintenance). OAM cells do not help segmentation and reassembly.

OAM&P

Operations, Administration, Maintenance and Provisioning
A set of network management functions and services that interact to provide the necessary network management tools and control. See NMS.

OC-1

Optical Carrier 1 (network)
ITU-TSS physical standard for optical fiber used in transmission systems operating at 51.84 Mbps.

OC-n

Optical Carrier
Fundamental unit in the SONET (Synchronous Optical Network) hierarchy. OC indicates an optical signal and n represents increments of 51.84 Mbit/s. Thus, OC-1, -3, and -12 equal optical signals of 51, 155,and 622 Mbit/s. The optical counterpart of STS-n.

Octet (network)

8 bits or one byte. This term is used in networking, in preference to byte, because some systems use the term "byte" for things that are not 8 bits long. Hence, "octet" is less confusing.

ODBC

Open Databases Connectivity
Software interface developed by Microsoft to connect to a database. It is competing with IDAPI.

ODI

Open Data-link Interface (network)
Novell specification for a multi-protocol API allowing NetWare and other transport protocols to share a common network interface card for PCs on a LAN.

Off-Line

Not directly connected to the computer (e.g., an off-line tape drive), or with connection suspended ("take the printer off-line").

OID

Object IDentifier (network management, MIB)
The address of a MIB variable.

OLE

Object Linking and Embedding
Windows' feature that allows applications to share information, even from different contexts and applications.

OLTP

On Line Transaction Processing

OMG

Object Management Group (standard, vendor consortium)
Vendor consortium organisation on Object-oriented Standards.
OMG Web site: http://www.omg.org/

ONA

Open Network Architecture

On-Line

Ready for use or Accessible via a computer (or terminal), rather than on paper or other medium.
This also means "interactive" as opposed to batch.

ONP

Open Network Provision
Set of rules established by the EU to regulate the access to public networks.

OOF

Out-Of-Frame (physical layer, alarm)

(The) Open Group (standard, vendor consortium)

Vendor consortium organisation on open systems.
Open Group Web site: http://www.opengroup.org/.

Openview

Network administration system developed by Hewlett-Packard. It is based on SNMP.

ORB

Object Request Broker (operating system)

OSF

Open Software Foundation (standard, body)
Consortium that originally developed Motif, OSF/1, DCE (Distributed Computing Environment) and CDE (Common Desktop Environment).

OSI

Open Systems Interconnection (normalization, network)
The OSI Reference Model of network architecture and a suite of protocols (protocol stack) to implement it were developed by ISO in 1978 as a framework for international standards in heterogeneous computer network architecture.
The architecture is split between seven layers:

application layer

presentation layer

session layer

transport layer

network layer

datalink layer

physical layer

Each specifying the protocols and functions required for two nodes to communicate using the underlying network infrastructure (physical medium, switches, routers, bridges, multiplexers, intermediate nodes).
Each layer uses the layer immediately below it and provides a service to the layer above. See also OSIRM.

OSPF

Open Shortest Path First Protocol (network, Internet, routing protocol)
A routing algorithm for IP that incorporates least-cost, equal-cost, and load balancing.

OSIRM

Open Systems Interconnection Reference Model
See OSI.

OUI

Organzationally Unique Identifier (network)
See RFC 1483.

OURS

Open User Recommended Solutions (information technology, standard, vendor consortium)
Vendor consortium organisation on information technology.
Web site: http://www.ours.org/.

Overhead (communications)

All information, such as control, routing, and error-checking characters, added by transmission protocols in addition to user-transmitted data; includes information that carries network status or operational instructions, network routing information, and retransmissions of user data messages that are received in error.

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