Glossary- O
A Data Communication Historical Series
By Bob Pollard

HOME                          INDEX

OADM:

Optical Add Drop Multiplexer: Optical multiplexing equipment that provides interfaces between different signals in a network.

OAI:

See Open Application Interface

OAKLEY:

Key establishment protocol based on the Diffie-Hellman algorithm and designed to be a compatible component of ISAKMP (Internet Security Association and Key Management Protocol).

OAM CELL:

Operation, Administration, and Maintenance Cell: ATM Forum specification for cells used to monitor virtual circuits. OAM cells provide a virtual circuit-level loop-back in which a router responds to the cells, demonstrating that the circuit is up and the router is operational.

OAM&P:

Operations, Administration, Management, and Provisioning: Provides the facilities and the personnel required to manage a network.

OARNET:

Ohio Academic Resources Network: Internet service provider that connects a number of U.S. sites, including the Ohio supercomputer center in Columbus, Ohio.

OAS:

See Office Automation Systems

OASD:

Office of the Assistant Secretary of Defense

OASD C3I:

Office of the Assistant Secretary of Defense for Command, Control and Communications, which is responsible, as required, for providing programmatic, policy, and acquisition guidance and oversight for DMS Organizational Message Service; ensures all organizational messages are prepared, validated, sent, and received reliably, regardless of origin or destination.

OBC:

Out-of-Band Control: Refers to the standard method of issuing MICA technology commands on the control channel, versus IBC, on the in-band data channel. Out-of-band commands are passed through the MICA mailbox mechanism.

OBJECT:

An entity, such as a file, folder, shared folder, printer, or Active Directory object described by a distinct, named set of attributes. For example: the attributes of a File object include its name, location, and size; the attributes of an Active Directory User object might include the user's first name, last name, and e-mail address. For OLE and ActiveX, an object can also be any piece of information that can be linked to, or embedded into, another object.

OBJECT CODE:

An executable machine code, derived from the output of a translating program such as an assembler or a compiler. Contrast with source code.

OBJECT IDENTIFIER:

See OID

OBJECT INSTANCE:

Network management term referring to an instance (occurrence) of an object type that has been bound to a value

OBJECT PROGRAM:

The machine language: Binary version of an assembly language program that can be internally deciphered by the computer.

OBJECT REQUEST BROKER (ORB):

A protocol: Redirects and routes received-real-time messages.

OC:

Optical Carrier: Series of physical protocols (OC-1, OC-2, OC-3, etc), defined for SONET optical signal transmissions. OC signal levels put STS frames onto multimode fiber-optic lines at a variety of speeds. The base rate is 51.84 Mbps (OC-1); each signal level thereafter operates at a speed divisible by that number (OC-3 =155.52 Mbps). See Optical Carrier

OCC:

1) Originating Call Control

2) See Other Common Carriers

OCLC:

Online Computer Library Catalog: Nonprofit membership organization offering computer-based services to libraries, educational organizations, and their users.

OC-n:

SONET optical carrier, Level n: Such as n = 3, 12, 48, 192, etc

OCR:

See Optical Character Recognition

OCTAL:

A numbering system with a base number of 8 (8 state); digital system 0-7

OCTC:

Operator's Console Transfer Channel: The interface between the Operators console and the computer.

OCTET:

A data unit composed of eight ordered bits, similar to one byte or a pair of data symbols in a Fiber Distributed Data Interface (FDDI).

8 bits: In networking, the term octet often is used, rather than byte, because some machine architectures employ bytes that are not 8 bits long.

OCU:

See Office Channel Unit

ODA:

Open Document Architecture: ISO standard that specifies how documents are represented and transmitted electronically.

ODBC:

Open Data-Base Connectivity: Standard application programming interface for accessing data in both relational and non-relational database management systems. Using this application programming interface, database applications can access data stored in database management systems on a variety of computers, even if each database management system use different data storage formats and programming interfaces.

ODBC is based on the call level interface specification of the X/Open SQL Access Group and was developed by Digital Equipment Corporation, Lotus, Microsoft, and Sybase.

ODI (ODLI):

See Open Data Link Interface

OEM:

See Original Equipment Manufacturer

OEMI CHANNEL:

Sane as Block Multiplexer Channel: An IBM term used to describe a multiplexer channel that interleaves blocks of data.

OFA:

Optical Fiber Amplifier: A device that amplifies an optical signal directly, without the need to convert it to an electrical signal, amplify it electrically, and reconvert is to an optical signal.

OFDM:

Orthogonal Frequency-Division Multiplexing: Is similar to the technology used in a DSL (Digital Subscriber Line) MODEM. OFDM is a variation of the Frequency-Division Multiplexing (FDM) used in phone-line networking. FDM puts computer data on separate frequencies from the voice signals being carried by the phone line, separating the extra signal space on a typical phone line into distinct data channels by splitting total bandwidth into uniform individual portions (sub-bands).

OFF- HOOK:

An activated telephone set or a MODEM automatically answering a call. Contrast with on-hook.

Call condition in which transmission facilities are already in use. Also known as busy.

OFFICE DOCUMENT ARCHITECTURE:

See ODA

OFFLINE / OFF-LINE:

1) A state that marks a component in a cluster as unavailable: A node in an offline state is either inactive or not running. Resources and groups also have an offline state.

2) May refer to peripheral equipment not being serviced (used) by the central processor and is available to other systems. Also, may refer to terminal equipment not connected to a transmission line.

OFF LOADING / OFF LOADED:

A process where a device is relieved of certain processing tasks, so that another (possibly less expensive) device can assume those duties.

OFF-NET:

A term used to indicate a location is beyond the primary serving area of a Dataphone Digital Service (DDS).

OFF-THE-SHELF:

Refers to Items (equipment/software) that are ready to operate and immediately accessible from stock.

OFFICE AUTOMATION SYSTEM (OAS):

Computer based word processors, spreadsheets, communications, etc. that make office activities more efficient.

OFFICE CHANNEL UNIT (OCU):

A terminal in a central office or DDS serving an end office that provides Dataphone Digital Service (DDS) circuit accesses.

OFFICE SYSTEMS NODE (OSN):

An IBM specified concept describing a set of functions and services provided to connect nodes in an IBM office system.

OIC:

Officer in Charge: Military or civilian.

OID:

Object Identifier: Values are defined in specific MIB modules. The Event MIB allows a user or an NMS to watch over specified objects and to set event triggers based on existence, threshold, and Boolean tests. An event occurs when a trigger is fired; this means that a specified test on an object returns a value of true. To create a trigger, a user or an NMS configures a trigger entry in the mte-Trigger-Table of the Event MIB. This trigger entry specifies the OID of the object to be watched. For each trigger entry type, corresponding tables, existence, threshold, and Boolean tables, are populated with the information required for carrying out the test. The MIB can be configured so that when triggers are activated (fired) either an SNMP Set is performed, a notification is sent out to the interested host, or both.

OIM:

OSI Internet Management: Group tasked with specifying ways in which OSI network management protocols can be used to manage TCP/IP networks.

OIR:

Online Insertion and Removal: Feature that permits the addition, the replacement, or the removal of cards without interrupting the system power, entering console commands, or causing other software or interfaces to shutdown.

OLE

Refers to a way to transfer and share information between applications by pasting information created in one application into a document created in another application, such as a spreadsheet or word processing file.

OLEX:

On Line Exerciser: The final stage for the development of the AAMPS maintenance programs was to grab some idle time during the online message switching control program cycle. At the end of each message processing cycle, a ledger of all system statistics was written to rotating drum storage memory. This was done to facilitate a failure recovery by using the previous cycle's ledger information. During this Ledger Write interval, a certain amount of non-processing, or cycle dead time, was found to be available. OLEX was developed and installed as part of the Processors Operating Program. OLEX was a fast and efficient hardware exerciser. It contained a set of routines that could perform tests on certain areas of CDP hardware, which allowed it to examine the online computer's state-of-health during each processing cycle.

OLO:

Other Local Operator

OLR:

Off-Line Reader: Software that will collect messages from mail, newsgroups, and message bases, and send newly written messages, and allow a response offline.

OLTP:

Online Transaction Processing: A system that processes transactions the instant the computer receives them and updates master files immediately. OLTP is essential for good financial record keeping and inventory tracking.

O&M:

Operations and Maintenance

OMG:

Object Management Group

OMTN:

Other Military Type Network

ON-ACCESS SCANNER:

A real-time virus scanner that scans disks and files automatically and often in the background: An on-access scanner scans files for viruses as the computer accesses the files.

ONC:

Open Network Computing: Distributed applications architecture designed by Sun Microsystems, currently controlled by a consortium led by Sun. The NFS protocols are part of ONC.

ON-DEMAND SCANNER:

A virus scanner the user starts manually. Most on-demand scanners allow the user to set various configurations and to scan specific files, folders or disks.

ON HOOK:

1) Condition that exists when a receiver or a handset is resting on the switch-hook, or is not in use.

2) Idle state (open loop) of a single telephone or private branch exchange (PBX) line loop

ON-NET:

A term used to indicate a location is within the primary serving area of a Dataphone Digital Service (DDS).

1-PERSISTENT:

A term used in a LAN (Local Area Network) environment; See persistent.

100baseT

The Ethernet standard for Local Area Networks (LAN) using twisted-pair cable: Can carry data at 100 megabits per second (Mbps).

ONE WAY CHANNEL:

A channel (line/terminal): Permits transmission in one direction only. See Simplex

ONE-WAY ENCRYPTION:

Irreversible transformation of plaintext to cipher-text: Such that the plain-text cannot be recovered from the cipher-text by other than exhaustive procedures even if the cryptographic key is known.

ONES DENSITY:

Scheme that allows a CSU/DSU to recover the data clock reliably: The CSU/DSU derives the data clock from the data that passes through it. To recover the clock, the CSU/DSU hardware must receive at least one 1 bit value for every 8 bits of data that pass through it.

ONLINE:

1) A condition where a device (peripheral/terminal) is connected and accessible by a processor (computer) and not available to other systems for off-line work.

2) A connection to the Internet ‘Online’

ONLINE INSERTION AND REMOVAL (OIR):

See OIR

ONLINE PROCESSING:

Refers to the processing of remote and local input data by a central processor, which would also be under the direct management of the central processor.

ONMA: See Open Network Management Architecture

ON-NET:

A term used to define any location that is beyond the primary serving area of a DDS. Contrast with off-net.

ONP:

See Open Network Provision

OOF: See Out-Of Frame

OOP:

Object Oriented Programming

OOS:

1) Out-of-Service.

2) Telecommunications: Out-of-Service signaling.

OOTB:

Out-of-The-Box: Default configuration for a product when it is first installed.

OPC:

Own Point Code: Point code of the Cisco SC2200 signaling controller

OPI:

Open Peripheral Interface: Cisco proprietary interface between Peripheral Gateways (PG) and the ICM(s) Central Controller.

OPEN ACCESS:

The availability of unrestricted access to a telecommunications service: Open access enables competitive access providers and other local service competitors to interconnect and operate within the public switched network.

OPEN AIR TRANSMISSION:

Data communications media using radio frequency (RF) signaling: infrared, microwave, satellite, T V and radio.

OPEN APPLICATION INTERFACE (OAI):

A program (window) in a computer that performs the private branch exchange (PBX) function.

OPEN ARCHITECTURE:

Refers to a network structure in which network hardware and software are based on industry standards that provides multi-vendor compatibility.

Architecture which third-party developers can legally use to develop products and public domain specifications exist

OPEN CIRCUIT:

Broken path along a transmission medium: Open circuits (non-usable) prevent network communication on the line in question

OPEN CONTENT:

Copyrighted information that is made available by the copyright owner to the general public under license terms that allow reuse of the material often with the requirement that a user must grant the public the same rights to a version modified by the user. Information that is in the Public Domain might also be considered a form of Open Content.

OPEN DATABASE CONNECTIVITY:

See ODBC

OPEN DATA LINK INTERFACE (ODI):

1) Network architecture: Allows multiple network protocols and LAN adapters to be used concurrently on the same workstation or file server.

2) Novell specification providing a standardized interface for NIC(s) (Network Interface Cards) that allows multiple protocols to use a single NIC

OPEN DOCUMENT ARCHITECTURE:

See ODA

OPEN GROUP:

Group formed in February 1996 by the consolidation of the two leading open systems consortia: X/Open Company Ltd (X/Open) and the Open Software Foundation (OSF).

OPEN INTER-NETWORK ACCESSIBILITY:

A network user’s operational capability to access other or different networks

OPEN NETWORK ARCHITECTURE:

The basic network facilities designed to permit usage by a Local Exchange Carrier (LEC) and competitors on an un-bundled basis; a set of provisions imposed by the Federal Communications Commission (FCC).

OPEN NETWORK COMPUTING:

See ONC

OPEN NETWORK MANAGEMENT ARCHITECTURE (ONMA)

Refers to IBM network management architecture consisting of Entry Points, Service Points and Focal Points, and implemented as NetView.

OPEN NETWORK PROVISION (ONP):

A Public Telecommunications Network / Public Telecommunications Services regulatory concept; introduced by the Commission of the European Communities.

OPEN SHORTEST PATH FIRST (OSPF):

A router function: Permits routers to exchange network configuration data in Transmission Control Protocol/Internet Protocol (TCP/IP) networks.

OPEN SOFTWARE FOUNDATION (OSF):

A group of hardware manufacturers that have established common standards for various systems that includes operating systems and networks; The OSF has previously defined the Distributed Computing Environment.

OPEN SOURCE SOFTWARE:

Refers to software where the underlying programming code is available to the users. The user may read it, make changes to it, and build new versions of the software incorporating the new changes. There are many types of Open Source Software, mainly differing in the licensing term under which (altered) copies of the source code may (or must) be re-distributed.

OPEN SYSTEM:

A system that provides operational compatibility among different Vendors equipment

OPEN SYSTEM INTERCONNECTIONS (OSI):

The International Standards Organization (ISO) model that defines standards for communicating between systems manufactured by different companies: OSI standards consist of seven layers used to perform different functions in data communications. Each layer performs a specific data communications function. Each of these layer’s, builds on the one below it. Although each step must be performed in order and each layer provides several options. The first three layers are physical, data link, and network, all of which are concerned with data transmission and routing. The fourth layer, transmission, provides an interface between the first three layers and last three layers. The last three layers are session, presentation, and application. These layers focus on user applications.

OPEN TYPE FONTS:

1) Outline fonts that are rendered from line and curve commands, and can be scaled and rotated.

2) Open Type fonts are clear and readable in all sizes and on all output devices supported by Windows. Open Type is an extension of TrueType font technology.

OPEN WIRE:

A description used to define a transmission line(s) supported separately on a pole above the ground. Or in maintenance terms an “open wire or circuit”, no current.

OPERAND(S):

The entity on which operations are performed

 OPERATING SYSTEM (OS):

The computer control program consisting of tasks or processes used in the performance of various processing, supervisory and control functions; this would include, hardware device allocation, access to software resources, message processing, security, etc.

OPERATION CODE / OP CODE:

The part of a computer instruction which specifies what operation has to be performed on the operands.

OPERATIONAL INTEGRATION:

Refers to a systems capability to allow several telecommunications media to operate as a single unit (network or system).

OPERATORS:

1) In mathematics and in programming and computer applications: A symbol or other character indicating an operation that acts on one or more elements. For example: the following four operators are used in standard calculations: / divide; * multiply; - subtract; + add.

2) For Indexing Service: a word or character that specifies a relationship in a query.

OPS/INE:

Operations Provisioning System / intelligent Network Element: Bellcore OSS that provides provisioning services for intelligent network elements.

OPT:

Cisco's Open Packet Telephony architecture

OPTICAL CARRIER (OC):

Defined transport levels for synchronous optical networks (SONET).

OPTICAL CHARACTER RECOGNITION (OCR):

A software function of converting scanned images into text files, which can be processed.

OPTICAL FIBER (Fiber Optic cable):

The thin filaments of glass, glass strands, contained within a shielded cable, each strand being an independent circuit for transmission of very wide frequency ranges. Optical fiber is contained in a shielded fiber optic cable for communications use.

OPTIMIZED BANDWIDTH MANAGEMENT:  

Refers to Cisco wide-area switches that ensure fair and cost-efficient bandwidth utilization using various techniques: ABR (Available Bit Rate) and Optimized Bandwidth Management are used for ATM and Frame Relay traffic. ABR is a standards-based ATM traffic management mechanism, and Fore-Sight is Cisco's implementation that mirrors ABR capabilities for Frame Relay traffic. ABR and Optimized Bandwidth Management optimize real-time traffic performance and throughput, and minimize data loss. Bandwidth management for voice is achieved through the use of standards-based voice compression and silence suppression mechanisms for circuit data services.

ORB:

See Object Request Broker

 ORIGINAL EQUIPMENT MANUFACTURE (OEM):

Refers to equipment manufactured and marketed by a vendor other than the original manufacturer.

ORPHAN FILE:

A file that is stored inside My Briefcase (file) and not linked to any file outside My Briefcase: The orphan file is not synchronized with any other file.

OSF:

Open Software Foundation: Group responsible for the Distributed Computing Environment (DCE) and the Distributed Management Environment (DME). See Open Software Foundation

OSI:

1) Open System Interconnection: A term that refers to a set of protocols as well as a communication reference model created and promulgated by ISO.

2) International standardization program created by ISO and ITU-T to develop standards for data networking that facilitate multi-vendor equipment interoperability.

OSI MODEL:

Open Systems Interconnection Model: The 7-layer reference model recommended by the ISO to provide a logical structure for network operations protocol.

OSI NETWORK ADDRESS:

Address, consisting of up to 20 octets, used to locate an OSI Transport entity. The address is formatted into two parts: an Initial Domain Part that is standardized for each of several addressing domains and a Domain Specific Part that is the responsibility of the addressing authority for that domain.

OSI PRESENTATION ADDRESS:

Open System Interconnection Presentation Address used to locate an OSI Application entity: It consists of an OSI Network Address and up to three selectors, one each for use by the transport, session, and presentation entities.

OSI REFERENCE MODEL:

Open System Interconnection Reference Model: Network architectural model developed by ISO and ITU-T. The model consists of seven layers, each of which specifies particular network functions, such as addressing, flow control, error control, encapsulation, and reliable message transfer. The lowest layer (physical layer) is closest to the media technology. The lower two layers are implemented in hardware and software whereas the upper five layers are implemented only in software. The highest layer (application layer) is closest to the user. The OSI reference model is used universally as a method for teaching and understanding network functionality.

OSINET:

International association designs used to promote OSI in vendor architecture

OSP:

1) On-Site Programmer

2) Open Settlement Protocol: Client/server protocol that establish authenticated connections between gateways, and allows gateways and servers to transfer accounting and routing information securely. OSP allows service providers to roll out VoIP services without establishing direct peering agreements.

OSPF:

Open Shortest Path First: Link-state, hierarchical IGP routing algorithm proposed as a successor to RIP in the Internet community. OSPF features include least-cost routing, multi-path routing, and load balancing. OSPF was derived from an early version of the IS-IS protocol.

See Open Shortest Path First

OSS:

Operations Support System: Network management system supporting a specific management function, such as alarm surveillance and provisioning, in a carrier network. Many OSS(s) are large centralized systems running on mainframes or minicomputers. See REACT 2000 and REACT 2001

OSSI:

Operations Support System Interface: DOCSIS specification. For example: DOCSIS OSSI 1.0 defines the network management requirements for support in a DOCSIS 1.0 environment.

OS/2:

A protected mode, virtual memory, multitasking operating system for personal computers based on the Intel 80286, 80386, i486, and Pentium processors. OS/2 can run most MS-DOS-based programs and can read all MS-DOS disks.

OTHER COMMON CARRIERS (OCC):

1) Past usage: A Company, other than AT&T, that has its own long-distance circuits, either owned or leased.

2) A term used to include domestic and International Record Carriers (IRC), Specialized Common Carriers (SCC), and domestic satellite carriers

OUI:

Organizational Unique Identifier: Three octets in a block of 48-bit LAN addresses.

OUT OF BAND:

Refers to frequencies outside the normal voice band

OUT OF BAND SIGNALING:

Transmission using frequencies or channels outside the frequencies or channels normally used for information transfer: Out-of-band signaling often is used for error reporting.

OUT-OF-FRAME (OOF):

A circuit or device framing condition counter that increases by one with each change in the framing status.

OUTFRAME:

Maximum number of outstanding frames allowed in a SNA PU 2 server at any time

OUTPULSE RULE:

Sequence of instructions that define autonomous call processing actions to be completed on outgoing ports in the Cisco VCO/4K switch.

OUTPUT:

1) The process of transferring data from an internal storage to an external storage device.

2) Output Devices – Devices that receive information from the computer, Example: Disk, Magnetic Tape, Printer, etc.

3) Output Circuit/Station – Communications link between the station and the computer over which data is sent to the station (terminal).

OUTSTATION:

Terminal, Tributary or Compound Terminal: A remote send/receive device or unit.

OVERLAP:

A mode where call control is waiting for possible additional call information from the preceding PINX (Private Integrated Services Network Exchange): This occurs because it received acknowledgment that the subsequent PINX can receive additional call information.

OVERFLOW STORAGE:

A Switching Center Overload protection function: When message load for one or more channels, or the entire switching center, is so high saturation of the center intrinsic storage space may result, causing a denial of service. Normally messages would be routed, low priority first, to magnetic tape or associated magnetic disk for future reentry into the system.

OVERHEAD/OVERHEAD BIT:

Additional non user information (bits/characters) that that may be transmitted, which may be added to the user originated/transmitted data. Overhead includes information that carries network status or operational instructions, network routing information, control characters, MODEM signals and re-transmission of data messages that are received in error.

OVERBUILD:

Adding capacity to a telecommunications network by increasing the capacity of existing facilities

OVERFLOW:

Excess traffic on a particular route that is transferred to another route for completion

OVERLOAD:

Exceeding the operational capacity of a computer (software/hardware) system; or excessive activity on a Network causing calls to be blocked.

OVERRIDE:

Refers to the seizure of a circuit or facilities even though it is already occupied

OVERRUN:

The resulting data loss when a receiving device is unable to accept data at the speed of the transmitting device.

OVERSAMPLING:

A method used in TDM (time Division Multiplexing) where each bit from each channel may be sampled more than once.

OVERSPEED:

A situation where transmitting devices would operate at a slightly faster speed than the data sent for transmission; a MODEM and a PABX have over-speeds of 0.1% and 0.5% respectively.

OVERWRITING VIRUS:

An overwriting virus copies its code over the host data files, thus destroying the original program. Disinfection is possible, although files cannot be recovered. It is usually necessary to delete the original file and replace it with a clean copy.