OARnet OBC Object instance
OCLC OCR Octet
ODA ODBC ODI
OEM OIM OIW
OLE ONC ones density
ONN Optical Network Unit OOFS
OOP open architecture open circuit
OPROM optical fiber
OS OS/2 OSF
OSI OSINET OSI Network Address
OSI Presentat. Address OSI reference model OSLOnett
OSPF outframe out-of-band signaling
OARnet (Ohio Academic
resources Network). Connects sites, including the Ohio supercomputer center
OBC (On-Board Computer).
Object instance Network
management term referring to an instance of an object type that has been
bound to a value.
OCLC (Online Computer Library
Catalog). OCLC is a nonprofit membership organization offering computer-
based services to libraries, educational organizations, and their users.
The OCLC library information network connects more than 10,000 libraries
worldwide. Libraries use the OCLC System for cataloging, interlibrary loan,
collection development, bibliographic verification, and reference searching.
OCR (Optical Character Recognition).
Octet An octet is 8 bits.
This term is used in networking, rather than byte, because some systems
have bytes that are not 8 bits long. [Source: RFC1392]
ODA (Office Documentation
Architecture). OSI standard that specifies
how documents are transmitted electronically.
ODBC (Open Database Connectivity).
A Windows extension.
ODI (Open Data-link
Interface). Novell specification providing a standardized way to access
OEM (Original-Equipment Manufacturer).
OIM (OSI Internet Management).
A group tasked with specifying ways in which OSI
network management protocols can be used to manage TCP/IP
OIW (Workshop for Implementors
of OSI). Frequently called NIST
OIW or the NIST Workshop, this is the North American regional forum at
which OSI implementation agreements are decided. It is equivalent to EWOS
in Europe and AOW in the Pacific.
OLE (Object Linking and Embedding).
ONC (Open Network Computing).
A distributed applications architecture promoted and controlled by a consortium
led by Sun Microsystems. The NFS protocols
are part of ONC.
ones density See pulse
Open Network Node that provides routing and directory services for APPN
End Nodes (EN) and Low
Entry Nodes (LEN).
Counterpart to APPN's network node (NN). On the network side,
an ONN uses TCP/IP transport and routing capabilities.
ONU (Optical Network
Unit) A form of Access Node that converts optical signals transmitted
via fiber to electrical signals that can be transmitted via coaxial cable
or twisted pair copper wiring to individual subscribers.[Source: ADSL
OOFS (Object-Oriented File
OOP (Object-Oriented Programming).
A method of programming in which the basic elements are modules, or objects,
with their own data structures and programming code, that can interact
with one another to add new features or be grouped together to form a program.
open architecture An architecture
according to which third-party developers can legally develop products
and for which public domain specifications exist.
open circuit A broken
path along a transmission medium. Open circuits will usually prevent network
OPROM (Optical Programmable
optical fiber See fiber-optic-cable.
OS (Operating System).
OS/2 (Operating System 2).
OSF (Open Software Foundation).
A consortium led by Digital, IBM and Hewlett Packard.
OSI (Open Systems Interconnection).
A suite of protocols, designed by ISO committees, to be the international
standard computer network architecture. See also: International
Organization for Standardization. [Source: RFC1392]
Reference Model A seven-layer structure designed to describe computer
network architectures and the way that data passes through them. This model
was developed by the ISO in 1978 to clearly define the interfaces in multivendor
networks, and to provide users of those networks with conceptual guidelines
in the construction of such networks. See also: International
Organization for Standardization. [Source: NNSC]
association designed to promote OSI in vendor architectures.
OSI Network Address
The address, consisting of up to 20 octets, used to locate an
OSI Transport entity. The address is formatted into an Initial Domain Part
which is standardized for each of several addressing domains, and a Domain
Specific Part which is the responsibility of the addressing authority for
Address The 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 A
network architectural model developed by ISO
and CCITT. 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 highest layer (the application layer) is closest to the media technology.
The OSI reference model is used universally as a method for teaching and
understanding network functionality.
Internet service provider in Norway, with "home base" in Oslo (as the name
should indicate). Currently has a large chunk of the dial-up Internet access
market in Norway.
OSPF (Open Shortest-Path
First Interior Gateway Protocol). A link state, as opposed to distance
vector, routing protocol. It is an Internet standard IGP defined in RFC
1247. See also: Interior Gateway Protocol,
Routing Information Protocol. [Source:
outframe Maximum number
of outstanding frames, allowed in an SNA PU2 server at any time.
out-of-band signaling Transmission
using frequencies or channels outside the normal frequencies or channels
used for information transfer. Out-of-band signaling is often used for
error reporting in situations in which in-band signaling can be effected
by whatever problems the network might be experiencing.
PABX pacing Packet
packet buffer Packet Switching PACNET
PAD page PAL
PAM parallel channel parallel transmission
parent directory Parity Bit parity check
password path control layer path control network
path cost pathname payload
PBX PC PCI
PCL PCM PCMCIA
PCX PD PDA
PDES PDF PDL
PDN PDS PDU
PEEL peer-to-peer computing PEM
performance management PERT peripheral node
P/F PGA PGC
phase PHIGS PHOTOSHOP
PHY physical address physical control layer
Physical Layer Physical Media physical medium
PHYSNET PIA PICS
piggybacking PIM PIN
PING PINGnet ping-ponging
PIPEX PIXAR PLA
PLANET On Line Ltd. PLC PLCP
PLD PLE Plesiochronous
PLOKT PL/1 PMMU
PNO Point Of Presence Point-to-Point (Link)
poison reverse updates Polling POP
port POS POSE
POSI POST PostScript
Postmaster POTS PPP
Presentation Address Presentation Layer presentation services layer
PRI primary station print server
priority queueing PRMD Probe
PROFS PROF-I-NET PROM
prompt propagation delay Prospero
protocol protocol address
protocol converter protocol stack protocol translator
Proxy Proxy ARP PSN
PSDN PSNP PSTN
PTT PU PU2.1
pulse density PUP PVC
PABX (Private Automatic
Branch eXchange). A private telephone exchange that automatically handles
calls to and from the public telephone network.
pacing IBM term for
flow control. See flow control.
Packet The unit of data
sent across a network. "Packet" a generic term used to describe unit of
data at all levels of the protocol stack, but it is most correctly used
to describe application data units. See also: Datagram,
frame. [Source: RFC1392]
packet buffer Storage
area to hold incoming data until the receiving device can process the data.
See also buffer.
Packet Switching (Message
Switching) A communications paradigm in which packets (messages)
are individually routed between hosts, with no previously established communication
path. See also: Circuit Switching,
Connectionless. [Source: RFC1392]
A communications technique in which messages of any length are cut into
packets, which are routed between hosts sharing the communication lines
of the network with other data flows. See also circuit
switching and message switching.
PACNET A New-Zeland-based
PAD (Packet Assembly/Disassembly).
Device used to connect simple device (like character-mode terminals) that
are by themselves not capable of assembling and disassembling packets to
X.25 networks. PADs buffer data sent between hosts and terminals across
an X.25 network, as defined by CCITT
Recommendation X.3, X.28,
page In UNIX a screen of
information in UNIXhelp. A screen may be scrollable.
PAL (Phase Alternate Line).
A European video standard.
Also: (Programmable Array Logic).
PAM (Pulse Amplitude
Modulation). Modulation scheme where the modulating wave is caused to modulate
the amplitude of a pulse stream.
parallel channel A
channel having a system/370 channel-to-control-unit I/O interface that
uses bus-and-tag cables as a transmission medium. See also bus
and tag channel.
parent directory In UNIX
the directory that is one level above the current directory.
parallel transmission The
simultaneous transmission of all bits making up a character or byte. See
also serial transmission.
Parity Bit An additional
non-information bit added to a group of bits to ensure that the total number
of 1 bits in the character is even or odd.
parity check A process
for checking the integrity of a character. A parity check involves appending
a bit that makes the total number of bynary "1" digits in a character or
word (excluding the parity bit) either odd (for "odd parity") or even (for
password A security
device consisting of a string of characters known only to the user and
the system. The user must supply this string when prompted to gain access
to the system. See also: login
path control layer Layer
3 in the SNA architectural model. This
is the SNA layer that routes packets through an internetwork.
path control network SNA
concept that consists of lower-level components that controlhe routing
and data flow through an SNA network and handle physical data transmission
between SNA nodes.
contrasts with NAUs, which
provide upper-level services.
path cost Arbitrary
value used as a routing metric to determine the best path to a destination.
See also routing metric.
payload The 192 bits
of information in a DS-1 frame.
pathname In UNIX a file
name given as the sequence of directories that lead to the file. A pathname
can be either a full pathname
or a relative pathname
PBX (Private Branch
Exchange). A telephone switchboard on the user premises.
PC (Personal Computer). Acronym
for computers which are compatible with the IBM pc or AT computers.
PCI (Protocol Control Information).
The protocol information added by an OSI entity to the service data unit
passed down from the layer above, all together forming a Protocol Data
Also: (Peripheral Component Interconnect).
PCL (Printer Control Language).
A proprietary command set used by programs to communicate with printers.
PCM (Pulse Code Modulation).
A procedure for adapting an analog signal (such as voice) into a 64 kbps
digital stream for transmission. The analog signal is sampled 8000 times
per second, and an 8-bit code is used to convert to digital.
PCMCIA (Personal Computer
Memory Card Interface Association).
PCX (PC Paintbrush). This
file format will write up to 24 bit images..
PD (Public Domain)
PDA (Personal Digital Assistant)
PDES (Product Data Exchange
PDF (Portable Document Format).
An Adobe Systems format for files may contain binary data either in strings
or in streams (which are used to represent images among other things).
PDL (Page-Description Language).
A programming language that describes output (e.g., type, sizes, fonts,
and graphics) to a display or printer.
PDN (Public Data Network).
A network operated either by a government (as in Europe) or by a private
concern to provide computer communications to the public, ususally for
a fee. PDNs enable small organizations to create a WAN without all the
equipment costs of long-distance circuits.
PDS (Promises Distribution
System). Wiring system developed and marketed by AT&T.
PDU (Protocol Data Unit).
"PDU" is International Standards Committee Speak for packet. See also:
packet. [Source: RFC1392]
PEEL (Programmable Electrically
peer-to-peer computing As
contrasted with client-server computing, peer-to-peer computing calls for
each network device to run both client and server portions of an application.
See also client-server computing. The phrase can also be used to describe
communication between implementations of the same OSI reference model layer
in two different network devices.
PEM (Privacy Enhanced Mail).
Internet email which provides confidentiality, authentication and message
integrity using various encryption methods. See also: Electronic
Mail, Encryption. [Source:
performance management One
of five categories of network management defined by ISO for management
of OSI networks.
Performance management subsystems are responsible for analyxing
and controlling network performance including network throughput and error
rates. See also accounting management,
configuration management, fault
management, and security management.
PERT (Program Evaluation
and Review Technique)
peripheral node In
SNA, a node that uses local addresses and is therefore not effected by
changes to network addresses. Peripheral nodes require boundary function
assistance from an adjacent subarea node.
P/F (Poll/Final bit).
A bit in bit-synchronous link-layer protocols that indicates the function
of a frame. If the frame is a response, a "1" in this bit indicates that
the current frame is the last frame in the response.
PGA (Pin Grid Array). A technique
of placing chips on boards in which the pins protrude from the bottom of
Also: (Professional Graphics Adapter). IBM's video interface card for
CAD applications, which provides 640-by
480-pixel resolution and supports 256 colors.
PGC (Professional Graphics
PGL (Professional Graphics
ph (short for phonebook).
A client to interrogate the phonebook database. See also CSO.
Also: (Parity High bit)
phase The location
of a position on an alternating wave form.
PHIGS (Programmer's Hierarchical
Interactive Graphics Standard). A standard graphics language that allows
applications to use a graphics coprocessor without having to rely on a
particular type of hardware.
format). This image file format is the only format that supports all of
the color modes including Duotones, Lab colors, and Multichannel. This
may be useful when working inside of Photoshop itself, however, this file
cannot be compressed and is not very compatible with other programs.
physical sublayer designation for FDDI
physical address Term
sometimes used to refer to the link-layer address of a network device.
Contrasts with a network or protocol address, which is a network-layer
address. See also hardware address.
physical control layer Layer
1 in the SNA architectural model. See physical
Physical Layer The
OSI layer that provides the means to activate and use physical connections
for bit transmission. In plain terms, the Physical Layer provides the procedures
for transferring a single bit across a Physical Media.
Physical Media Any
means in the physical world for transferring signals between OSI systems.
Considered to be outside the OSI Model, and therefore sometimes referred
to as "Layer 0." The physical connector to the media can be considered
as defining the bottom interface of the Physical Layer, i.e., the bottom
of the OSI.
physical medium See
PHYSNET Physics Network.
A group of many DECnet-based physics
research networks, including HEPnet.
PIA (Peripheral Interface
PICS (Platform for Internet
Content Selection). Is an infrastructure for associating labels with Internet
content. It was originally designed to help parents and teachers control
what children access on the Internet, but it also facilitates other uses
for labels, including code signing, privacy, and intellectual property
rights management. Source: [ W3ORG
PICS is an effort of the World Wide Web Consortium at MIT's Laboratory
for Computer Science, drawing on the resources of a broad cross-section
of the industry. Project history, a long list of supporting organizations,
and details of the specifications may be found at http://w3.org/PICS
PICT (Macintosh PICT format).
This is a widely used Macintosh file format which stores 16 or 32 bits
per pixel. It can also compress files using JPEG
PIF (Program Information
piggybacking The process
of carrying acknowledgments within a data packet to save network bandwidth.
PIM (Personal Information
PIN (Positive Intrinsic Negative).
PING (Packet InterNet Groper).
A program used to test reachability of destinations by sending them an
ICMP echo request and waiting for a reply. The term is used as a verb:
"Ping host X to see if it is up!" See also: Internet
Control Message Protocol. [Source: RFC1208]
A Swiss commercial internet provider.
used to describe the actions of a packet in a two-node routing loop.
(Public IP EXchange). The largest commercial Internet service
provider in the UK, and one of a number of Pan-European providers. A subsidiary
of Unipalm Group PLC
PIXAR (PIXAR file format)
- This image file format can be used for PIXAR's rendering and animation
PLA (Programmable Logic Array).
A French commercial Internet provider.
On Line Ltd. The Planet Online is a digital dial on demand
(using ISDN) service provider based
in Leeds, UK. We currently offer a number of total connectivity solutions.
Our pricing includes rental of the preconfigured hardware and software
that is neccessary to use Internet services via proxy.
PLC (Programmable Logic Controller).
PLCP (Physical Layer
Convergence Procedure). Mapping of cells to a specific physical transmission
medium (such as DS-3).
PLD (Programmable Logic Device).
PLE (Programmable Logic Element).
Plesiochronous A condition
in a synchronized digital network where communicating devices each are
synchronized to a different timing source of comparable accuracy and stability.
PLOKT Abbreviation of
press a lot of keys to abort.
PL/1 (Programming Language/1).
PMMU (Paged Memory Management
Unit). Hardware that handles functions related to the use of memory by
applications and virtual-memory operating systems.
PNG (Portable Network Graphics).
Is an extensible file format for the lossless, portable, well-compressed
storage of raster images. PNG provides a patent-free replacement for GIF
and can also replace many common uses of TIFF. Indexed-color, grayscale,
and truecolor images are supported, plus an optional alpha channel for
transparency. Sample depths range from 1 to 16 bits. The development of
the PNG specification was supported by W3C and by CompuServe - original
creators of the GIF format and now W3C Members - who both wished to see
PNG become accepted as the new Internet standard format for lossless graphics.
The official PNG home page
is maintained by Greg Roelofs and includes a frequently updated listing
of Web browsers that support PNG (including plug-ins), helper applications,
and content creation tools (both interactive editors and conversion tools)
Source: [ W3ORG ]
PNG, an extensible file format for the lossless, portable, well-compressed
storage of raster images. PNG provides a patent-free replacement for GIF
and can also replace many common uses of TIFF. Indexed-color, grayscale,
and truecolor images are supported, plus an optional alpha channel. Sample
depths range from 1 to 16 bits. Source: [RFC
PNO (Public Network Operator).
Usually a PSTN PTTs
of some sort.
Point Of Presence (POP)
A site where there exists a collection of telecommunications equipment,
usually digital leased lines and multi-protocol routers. [Source: RFC1392]
Point-to-Point (Link) A
connection between two, and only two pieces of equipment.
poison reverse updates Routing
updates that specifically indicate that a network or subnet is unreachable,
rather than implying that a network is unreachable by not including it
in updates. Poison reverse updates are sent to defeat large routing loops.
Working on the premise that increased route metrics generally indicate
routing loops. Cisco's IGRP implementation
sends poison reverse updates if a route metric has increasred by a factor
of 1.1 or greater.
Polling Connecting to
another system to check for things like mail or news. [Source: ZEN]
In Data Communications polling a means of controlling devices on a
multipoint line in a polling scheme each terminal is called in turn to
permit it to transmit information.
POP (Post Office
Protocol). A protocol designed to allow single user hosts to read
mail from a server. There are three versions: POP (RFC
918), POP2 (RFC
937), and POP3 (RFC
1939). Latter versions are NOT compatible with earlier versions. See
also: Electronic Mail.
Also: (Point Of Presence).
port A port is a transport
layer demultiplexing value. Each application has a unique port number associated
with it. See also: Transmission Control Protocol,
User Datagram Protocol. [Source:
3 meanings. First and most generally, a place where information goes
into or out of a computer, or both. E.g. the "serial port" on a personal
computer is where a modem would be connected. On the Internet "port" often
refers to a number that is part of a URL, appearing after a colon (:) right
after the domain name. Every service on an Internet server "listens" on
a particular port number on that server. Most services have standard port
number, e.g. Web servers normally listen on port 80. Services can also
listen on non-standard ports, in which case the port number must be specified
in a URL when accessing the server, so you might see a URL of the form:
gopher://gopher.cnuce.cnr.it:7000/ which shows a gopher server running
on a non-standard port (the standard gopher port is 70). Finally, "port"
also refers to translating a piece of software to bring it from one type
of computer system to another, e.g. to translate a Windows program so that
it will run on a Macintosh. See also: Domain,
POS (Programmable Option
POSE (Picture-Oriented Software
POSI (Promoting Conference
for OSI). The OSI "800-pound gorilla" in Japan. Consists of executives
from the six major Japanese computer manufacturers and Nippon Telephone
and Telegraph. They set policies and commit resources to promote OSI.
POST (Power-On Self Test)
PostScript A page
description language developed by Adobe System
Postmaster The person
responsible for taking care of electronic mail problems, answering queries
about users, and other related work at a site. [Source: ZEN]
POTS (Plain Old Telephone
Service). Standard analog telephone service used by many telephone companies
throughout the United States.
PPP (Point-to-Point Protocol).
The Point-to-Point Protocol, defined in RFC
1661, provides a standard method for transporting multi-protocol datagrams
over point-to-point links. See also: SLIP.
Presentation Layer The
OSI layer that determines how Application information is represented (i.e.,
encoded) while in transit between two end systems.
presentation services layer Layer
6 of the SNA architectural model. See presentation
PRI (Primary Rate Interface).
ISDN interface to primary rate access.
Primary rate access consists of a single 64-Kbps D channel plus 23 (in
the case of 1.544 Mbps) or 30 (in the case of 2.048 Mbps) B channels for
voice and/or data. See also basic rate
interface, BISDN, and ISDN.
primary station In
bit-synchronous link-layer protocols such as HDLC
and SDLC, station that controls
the transmission activity of secondary stations and performs other mangement
functions such as error control through polling or other means. Primary
stations send commands to secondary stations and receive responses. Also
called primaries. See also secondary
print server A networked
computer systems that fields, manages, and executes (or sends for execution)
print requests from other network devices.
priority queueing Routing
feature in which frames in an inteface output queue are prioritized based
on various features such as packet size and interface type.
PRMD (Private Management
Domain). An X.400 Message
Handling System private organization mail system. Example: NASAmail.
Probe An address resolution
protocol developed by Hewlett-Packard.
An Austrian Information Provider.
PROFS (PRofessional OFfice
PROM (Programmable Read-Only
prompt See: shell
propagation delay The
time required for data to travel over a network from source to ultimate
Prospero A distributed
filesystem which provides the user with the ability to create multiple
views of a single collection of files distributed across the Internet.
Prospero provides a file naming system, and file access is provided by
existing access methods (e.g., anonymous FTP and NFS). The Prospero protocol
is also used for communication between clients and servers in the archie
system. See also: Anonymous FTP,
Site, Gopher, Network
File System, Wide Area Information
Servers. [Source: RFC1392]
protocol A formal description
of message formats and the rules two computers must follow to exchange
those messages. Protocols can describe low-level details of machine-to-machine
interfaces (e.g., the order in which bits and bytes are sent across a wire)
or high-level exchanges between allocation programs (e.g., the way in which
two programs transfer a file across the Internet). [Source: MALAMUD]
protocol (file transfer) Many
protocols have been developed to ensure reliable data transfer at maximum
speed, among them XModem, YModem,
ZModem and Kermit.
With modern modems the use of integrated hardware protocols (MNP4
and V.42) is recommended. The G-flavors
of the above mentioned Ymodem and Zmodem allow transfers of multiple files
with no additional error correction.
protocol address See
protocol converter A
device/program which translates between different protocols which serve
similar functions (e.g., TCP and TP4).
protocol stack A
layered set of protocols which work together to provide a set of network
functions. See also: layer, protocol.
Examples include Apple Talk
protocol translator A
network device or software that converts one protocol into another, similar,
protocol. For example, the Cisco CPT
performs conversion between X.25
PAD and Telnet.
Proxy The mechanism whereby
one system "fronts for" another system in responding to protocol requests.
Proxy systems are used in network management to avoid having to implement
full protocol stacks in simple devices, such as modems.
Proxy ARP The technique
in which one machine, usually a router, answers ARP requests intended for
another machine. By "faking" its identity, the router accepts responsibility
for routing packets to the "real" destination. Proxy ARP allows a site
to use a single IP address with two physical networks. Subnetting would
normally be a better solution. See also: Address
Resolution Protocol. [Source: RFC1208]
PSN (Packet Switch Node).
A dedicated computer whose purpose is to accept, route and forward packets
in a packet switched network. See also: packet
switching, router. [Source: NNSC]
PSDN (Packet Switched Data
PSNP (Partial Sequence
Number). PDUs. Used to request LSPs
from one Integrated IS-IS another.
PSTN (Public Switched
Telephone Network). Refers to the telephone network.
PTT (Postal Telegraph and
Telephone). Outside the USA, PTT refers to a telephone service provider,
which is usually a monopoly, in a particular country. [Source: RFC1392]
PU (Physical Unit). SNA component
that manages the physical resources of node, as requested by a SSCP.
There is one PU per node.
PU2.1 (Physical Unit 2.1).
A type of network node used for connecting SNA nodes in a peer-oriented
network. APPN is based upon Node Type
2.1. Type 2.1 nodes can also be connected into a traditional hierarchical
pulse density Also
called ones density. A measure
of ones compared with the total number of digit time slots transmitted.
Some specifications require no more than 15 consecutive zeros, with an
average of 12.5% pulse density on T1 facilities.
PUP (PARC Universal
Protocol). A protocol similar to IP developed at Xerox Palo Alto Research
PVC (Permanent Virtual
Circuit). Generally, a virtual circuit that is permanently established.
PVCs save bandwidth associated with circuit astablishment and tear down
in those situations where certain virtual circuits must exist all the time.
Q.920/Q.921 Q.931 Q.93B
QEMM QLLC QOS
query queue queueing delay
queueing theory QuickTime
specifications for the user-network interface (UNI) data-link layer. See
recommendation. The standard for signaling to set up ISDN
recommendation that is a standard for signaling to set up ATM
virtual connections. An evolution of CCITT Recommendation Q.931.
QEMM (Quarterdeck Expanded
QLLC Qualified LLC.
OSI/SNA - IBM protocol use X.25 network as SNA data link.
QOS (Quality of Service).
A measure of performance for a transmission system that reflects its transmission
quality and availability of service.
query Message used
(usually in a request-response protocol) to inquire about the value of
some variable or set of variables.
queue Generally, an
ordered list of elements waiting to be processed. In routing, a backlog
of packets waiting to be forwarded over a router interface.
queueing delay The
amount of time that data must wait before it can be transmitted onto a
statistically multiplexed physical circuit.
queueing theory Scientific
principles governing the formation or lack of formation of congestion on
a network or at an interface.
QuickTime A movie format
developed by Apple Computer.