Glossary- P
A Data Communication Historical Series
By Bob Pollard

HOME                       INDEX

PABX:

Private Automatic Exchange or Exchange, Private Automatic:

See Exchange, Private Automatic or Private Automatic Exchange

PACING:

1) The process of sending a predefined quantity of information before an acknowledgment response has been received for the previously transmitted data, similar to Block by Block transmission.

2) Flow Control: Technique for ensuring that a transmitting entity, such as a modem, does not overwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed.

PACKAGE:

An icon that represents embedded or linked information. The information may consist of a complete file, such as a Paint bitmap, or part of a file, such as a spreadsheet cell. When a user chooses the package, the application used to create the object either plays the object (example: a sound file) or opens and displays the object. If a user changes the original information, linked information is automatically updated. However, a user must manually update embedded information.

PACKER:

A BBS program which packs new messages together for transmission later by a mailer or the messages may be downloaded by a user for off line mail reading.

PACKET:

Logical grouping of information that includes a header containing control information and (usually) user data: Packets often are used to refer to network layer units of data; the continuous stream of data sent or received over a circuit in a ‘Packet’ switching environment is broken into ‘packets’ (blocks). This would occur when sending or receiving data on the Internet. These packets contain control information, along with the text, about which computer sent the data and where the data is going. If an error occurs during transmission, the ‘Packet’ can attempt to find another route. When all the ‘Packets’ are delivered (received), the recipient computer reassembles all the ‘Packets’ in the original order, as sent.

PACKET ASSEMBLER/DIS-ASSEMBLER:

See PAD

PACKET ASSEMBLY UNIT:

A device or facility attached to a packet switched system that allows non packet-mode terminals to transmit and receive data with packet-mode terminals. See PAD

PACKET BUFFER:

Memory space reserved for storing a packet(s) awaiting transmission or for storing a received packet(s).

PACKET HEADER:

A term used in a packet-switched environment to describe the first three octets of an X.25 packet.

PACKET INTERNET GROUPER:

See PING

PACKET OF DISCONNECT (POD):

Process that allows a PPP session to be verified and then terminated by the network access server: It terminates connections on the network access server when particular session attributes are identified. The POD client, residing on a UNIX workstation, sends disconnect packets to the POD server running on the network access server using session information obtained from AAA. The network access server terminates any inbound user session with one or more matching key attributes. It rejects requests that do not have the required fields or where an exact match is not found.

PACKET SWITCHING:

WAN (Wide Area Network) that routes packets along the most efficient path and allows a communications channel to be shared by multiple connections: A transmission protocol in which data is segmented into packets that can be individually addressed and routed through the Packet Switched network and the routing may use several different routes as necessary. The sequence of the packets is maintained and the destination established by the exchange of control information, contained in the packets. The receiving-end node determines that all packets are received and in the proper sequence before forwarding the reassembled message to the addressee. See Packet, Packet Switching Network and PAD.

PACKET SWITCHING MODULE:

The Packet switching Module provides an interface between a PBX and the Packet Switching network interface. Data terminals are provided with the necessary speed (bit rates), codes, and protocols in order to process data calls to packet-switching networks.

PACKET SWITCHED NETWORK:

A communications network in which data is transmitted in predetermined packets (blocks). Packets can be routed individually over the best available network connection and reassembled to form a complete message at the destination. See Packet, Packet Switching and PAD.

PACKET SWITCHING NODE (PSN):

Individual termination points (connections) on a Packet Switch Network; or the name of an individual Arpanet packet switch.

PACKET TERMINAL:

Any DTE (Data Terminal Equipment) device able to transmit and receive packets

PACKING DENSITY:

The number of bits, characters or units of useful information contained within in a given linear dimension, such as the number of bits per inch of magnetic tape or number of bytes that can be stored on a disk.

PACING GROUP:

A term used in an IBM SNA environment to define the number of data units that can be sent before a returned response.

PAD:

Packet Assembler / Dis-assembler: A device that converts a serial data (character) stream from a terminal or host computer into packets that can be handled by a packet-switching network. It also can receive packets from the network, and disassembles them into character (data) streams that can be handled by the terminal or host computer. Header information is inserted in the transmitted packet to allow proper routing to the destination. See Packet and Packet Switching Network.

PAD CHARACTER:

A character normally sent at the beginning / end of a synchronous transmission to provide timing and bit synchronization.

PADDING:

A process where the communications program may add blank data (characters) to fill up a block when a file that is being transferred ends in the middle of the block. Some programs will strip these fill characters before saving the file to disk.

PAGE DESCRIPTION LANGUAGE (PDL):

A computer language that describes the arrangement of text and graphics on a printed page

PAGE FAULT:

The interrupt that occurs when software attempts to read from or write to a virtual memory location that is marked not present

PAGE FAULT DELTA:

In Task Manager, the change in the number of page faults since the last update.

PAGED POOL:

The system allocated virtual memory that can be paged. Paging is the moving of infrequently used parts of a programs working memory from RAM to another storage medium, usually the hard disk.

In Task Manager: the amount of system allocated virtual memory, in kilobytes, used by a process.

PAGING FILE:

A hidden file on the hard disk that Windows uses to hold parts of programs and data files that do not fit in memory: The paging file and physical memory, or RAM (Random Access Memory), comprise virtual memory. Windows moves data from the paging file to memory as needed and moves data from memory to the paging file to make room for new data. Paging file is also called a swap file.

PAgP:

Port Aggregation Protocol

PAL:

1) Phase Alternating Line: TV system used in most of Europe in which the color carrier phase definition changes in alternate scan lines; utilizes an 8 MHz-wide modulated signal.

2) Public Access Line

PAL FORMAT:

For Phase Alteration Line - 625 lines of resolution at 25 frames per second.

PAM:

1) Pulse Amplitude Modulation: A sampled analog signal which may exist prior to its coding and quantifying.

2) Pulse Amplitude Modulation: Modulation scheme where the information modulating wave modulates the amplitude of a pulse stream.

3) Port to Application Mapping: PAM allows the user to customize TCP or UDP port numbers for network services or applications.

PANOSE:

A font-classification method that measures values: such as serifs, weight, and stroke variations, for a TrueType font. These values are represented by a Panose number. The Panose number is then used to associate the font with other fonts of similar appearance but different names. The closer the Panose number of two fonts, the more similar they are.

PAP:

Password Authentication Protocol: Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and the host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access but merely identifies the remote end. The router or access server then determines whether that user is allowed access. PAP is supported only on PPP lines.

PAPER TAPE:

An input/output medium on which data would be recorded as a pattern of five or eight bit punched holes across the tape, i.e. Baudot code set, five bits and ASCII code set, eight bits.

PAPER TAPE READER:

A device capable of sensing information punched in a paper tape in the form of a series of holes. The holes are normally punched across the tape to represent characters. The width of the tape is determined by the device character code set, i.e. Baudot code set, five bits and ASCII code set, eight bits.

PARC UNIVERSAL PACKET (PUP):

An Internet system developed by the Xerox Corporation: The PUP is the fundamental unit of transfer, similar to the Internet Protocol (IP) data-gram in a Transmission Control Protocol / Internet Protocol (TCP/IP) Internet.

PARABOLIC ANTENNA:

Dish-like antenna that sends RF waves in a highly focused manner. Such antennas provide very large power gains and are highly efficient. This antenna is typically used by Cisco's LMDS, U-NII, and MMDS.

PARALLEL CHANNEL:

Channel that uses bus and tag cables as a transmission medium

PARALLEL INTERFACE:

An interface or circuit that can transmit/receive a group of bits (byte, character size) at the same time, by transmitting each bit over a separate wire.

PARALLEL PORT:

The input/output connector for a parallel interface device: Printers are generally plugged into a parallel port.

PARALLEL TRANSMISSION:

Simultaneous transmission of all data bits making up a character or byte, either over separate channels (lines) or on different carrier frequencies on one channel.

PARALLELISM:

Multiple paths between two points in a network: These paths might be of equal or unequal cost. Parallelism is often designed into a network because if one path fails, there is redundancy in the network to ensure that an alternate path to the same point exists.

PARC:

Palo Alto Research Center: Research and development center operated by XEROX. A number of widely used technologies were originally conceived at PARC, including the first personal computers and LAN(s).

PARENT PEER GROUP:  

In ATM, a peer group that acts as a ‘parent’ to a subordinate peer group. Organizing peer groups hierarchically reduces the exchange of PTSP(s).

PARTIAL MESH:

Network in which devices are organized in a mesh topology with some network nodes organized in a full mesh, while others are connected only to one or two other nodes in the network. A partial mesh does not provide the level of redundancy of a full mesh topology but is less expensive to implement. Partial mesh topologies generally are used in the peripheral networks that connect to a fully meshed backbone.

PARITY (Parity Bit):

A method used to determine if an error was introduced during data communications or internal processing. A method of error detection that uses an extra bit to make the total number of marking bits (1) in a character either odd or even. In the ASCII code set the 8th bit is normally used as the parity bit. If a character is transmitted with odd parity, it should be received with odd parity if no errors were introduced during the communications process. Internally within the computer architecture a parity bit is usually added to the transfer of information between memory to devices, devices to devices and devices to memory. Processing between internal computer registers may also involve parity checking. In a Packet switching environment a 2 or 4 byte error-check value is used to validate the entire Packet (block).

PARITY CHECK:

The examination of a character (byte) and its parity bit to determine if the character has been received correctly. A parity check involves appending a bit that makes the total number of binary 1 digits in a character, byte or word, excluding the parity bit, either odd (odd parity) or even (even parity) parity.

PARITY CHECK, HORIZONTAL:

A form of Longitudinal Redundancy Check (LRC) - A method for performing parity checks, where a parity check is applied to a group of particular bits from each character in a block.

See Longitudinal Redundancy Check (LRC)

PARITY CHECK, VERTICAL:

A method for performing a parity check where a parity check bit is added to the character bits creating an even or odd number of one bits; a function of character or group (block) Parity Checking. See VRC (Vertical Redundancy Check)

PARITY ERROR:

A data error where an extra or missing bit is detected

PART 68:

The FCC regulations permitting the registration of voice/data communications equipment provided they meet federal requirements designed to ensure no harm to the telephone network.

PARTITION:

A portion of a physical disk that functions as though it were a physically separate disk: After a user creates a partition, it must be formatted and assigned a drive letter before a user can store data on it.

On basic disks, partitions are known as basic volumes, which include primary partitions and logical drives. On dynamic disks, partitions are known as dynamic volumes, which include simple, striped, spanned, mirrored, and RAID-5 volumes.

PARTITIONED EMULATION PROGRAMMING EXTENSION (PEP):

IBM software used with the Network Control Program (NCP) to permit a communications controller to operate in a partitioned mode, controlling an SNA network while managing a number of non-SNA communications lines.

PASS-BAND:

A range of frequencies passed by a device or network

PASS-BAND FILTERS:

A filter used to allow only certain frequencies within the communications channel to pass while rejecting all frequencies outside the pass-band. Such filters may be internal to the MODEM or a separate device.

PASSWORD:

A security measure used to restrict logon names to user accounts and access to computer systems and resources. A password is a string of characters that must be provided before a logon name or an access is authorized. A password can be made up of letters, numbers, and symbols, and it is usually case sensitive.

PASSWORD ATTACKS:

A password attack is an attempt to obtain or decrypt a legitimate user's password. Hackers can use password dictionaries, cracking programs, and password ‘sniffers’ in password attacks. Defense against password attacks is rather limited but usually consists of a password policy including a minimum length, unrecognizable words, and frequent changes.

PASSWORD PROTECTION:

The use of system passwords as a security measure to protect against unauthorized access

PASSWORD SNIFFING:

The use of a ‘sniffer’ to capture passwords as they cross a network: The network could be a local area network, or the Internet itself. The sniffer can be hardware or software. Most sniffers are passive and only log passwords. The attacker must then analyze the logs later.

PATCH:

1) A temporary jack and patch cord connection, utilizing a jack matrix, such as in a Technical Control facility or Wire room.

2) A temporary or permanent computer program revision (program patch) inserted via an input device.

PATCHING JACKS:

A series-access (jack matrix) hardware device or cable, used to patch or bypass faulty equipment by using any available spare units.

PATH CONTROL LAYER:

Layer 3 in the SNA architectural model: This layer performs sequencing services related to proper data reassembly. The path control layer also is responsible for routing.

The network processing layer in an IBM SNA environment, handling the routing of data units through the communications network and also managing shared link resources.

PATH CONTROL NETWORK:

SNA concept consisting lower-level components that control the routing and data flow through an SNA network, and handles physical data transmission between SNA nodes.

PATH DISCOVERY:  

For a digital certificate: The process of finding a set of public-key certificates that comprise a certification path from a trusted key to a specific certificate.

PATH LOSS:

Power loss that occurs when Radio Frequency (RF) waves are transmitted through the air: This loss occurs because the atmosphere provides a filtering effect on the signal. Certain electromagnetic frequencies (very high / non-commercial) are completely blocked or filtered by the atmosphere.

PATH NAME:  

Full name of a DOS, Mac OS, or UNIX file or directory; including all directory and subdirectory names: Consecutive names in a path name typically are separated by a backslash (\) for DOS, a colon (:) for Mac OS, and a forward slash (/) for UNIX.

PATH STATE BLOCK(s):

Block maintained by RSVP to store a path.

PATH VALIDATION:

Process of validating all the digital certificates in a certification path, and determining the required relationships between those certificates; thus validating the contents of the last certificate on the path

PATS:

Personal AUTODIN Terminal System

PAX:

Private Automatic Exchange or Exchange, Private Automatic:

See Exchange, Private Automatic or Private Automatic Exchange

PAYLOAD:

Refers to the effects produced by a virus attack. Sometimes refers to a virus associated with a dropper or Trojan horse.

Portion of a cell, frame, or packet that contains upper-layer information (data)

PB:

PetaByte: 1 quadrillion bytes or one thousand terabytes.

PBX:

Private Branch Exchange: A telephone/data switching system, usually located on customer premises and belonging to the user.

PC:

See Personal Computer

PC CARD:

A removable device: Approximately the size of a credit card that can be plugged into a Personal Computer Memory Card International Association (PCMCIA) slot in a portable computer. PCMCIA devices can include MODEM, network cards, and hard disk drive interfaces. Also a term used for laptop NIC cards

PCI:

1) Protocol Control Information: Control information added to user data to comprise an OSI packet; the OSI equivalent of a header.

2) See Peripheral Component Interconnect

PCI EXPANSION SLOT:

A connection socket for a peripheral designed for the Peripheral Component Interconnect (PCI) local bus on a computer motherboard.

PCL:

Printer Control / Command Language

PCM:

1) Plug Compatible Machine: A device capable of being substituted in place of the original manufacturer's device.

2) Pulse Code Modulation: A form of digital modulation where an analog signal is sampled, each sample is quantified independently of other samples, and then it is converted to a digital signal. Technique of encoding analog voice into a 64-kbit data stream by sampling with eight-bit resolution at a rate of 8000 times per second.

3) See Physical Connection Management

PCMCIA DEVICE:

  Personal Computer Memory Card International Association: A removable device, approximately the size of a credit card that can be plugged into a PCMCIA slot in a portable computer. PCMCIA devices can include MODEM, network adapters, and hard disk drive interfaces.

  Some PCMCIA cards can be connected to and disconnected from the computer without restarting it. Before a user removes the PCMCIA card, however, one should use the Add Hardware Wizard to notify Windows that the card is being removed. Windows will then notify the user when the device can be removed.

PCR:

Peak Cell Rate: Parameter defined by the ATM Forum for ATM traffic management. In CBR (Constant Bit Rate)transmissions, PCR determines how often data samples are sent. In ABR (Available Bit Rate) transmissions, PCR determines the maximum value of the ACR.

PCS:

1) Personal Communications Service: Advanced network architecture that provides personal, terminal, and service mobility. In the United States, PCS spectrum has been allocated for broadband, narrowband, and unlicensed services.

2) Port Concentrator Switch.

See Personal Communications Service

PCU:

Packet Control Unit: Network component that normally resides in a BSC and directs packet traffic to the SGSN for processing by the GPRS network.

PDA:

See Personal Digital Assistant

PDF (pdf / pdf file):

Portable Document Format: A file format developed by Adobe Systems, that is used to capture almost any kind of document. Viewing a PDF file requires Acrobat Reader, which is built into some browsers or is free from Adobe.

PDM:

Pulse Duration Modulation or Possible Duplicate Message

PDN:

1) Public Data Network: Any network designed for the purpose of providing voice / data communications services to the public, such as packet- switching or digital DDS service. A PDN may be operated by common carriers, a PTT or private operating companies.

2) Public/private/packet data network: Represents a public or private packet-based network, such as an IP or X.25 network.

3) Packet Data Network: See packet-switched network

PDP:

1) Programmable Data Processor: A mini data processor manufactured by Digital (DEC).

2) Packet Data Protocol contest: Network protocol used by external packet data networks that communicate with a GPRS network. IP is an example of a PDP supported by GPRS. Refers to a set of information that describes a mobile wireless service call or session; normally used by mobile stations and GSN(s) in a GPRS network to identify the session

PDP 1105, PDP 1134:

A Mini-computer manufactured by Digital (DEC).

PDU:

See Protocol Data Unit

PEAK MEMORY USAGE:

In Task Manager, the peak amount of physical memory resident (utilized) in a process since it started.

PEAK RATE:

Maximum rate, in kilobits per second, at which a virtual circuit can transmit

PEER:

Router or device that participates as an endpoint in IP-Sec and IKE

PEER COMMUNICATIONS:

A form of communications in which two parties communicates with each other as equals rather than in a master/slave relationship. Peer communications protocols usually provide more powerful interaction facilities.

PEER GROUP:

Collection of ATM nodes that share identical topological databases and exchange full link state information with each other: Peer groups are arranged hierarchically to prevent excessive PTSP traffic.

PEER TO PEER COMPUTING:

Calls for each network device to run both client and server portions of an application. Also describes communication between the use of the same OSI reference model layer in two different network devices.

PEER-TO-PEER; PEER-TO-PEER MODEL; PEER-TO-PEER NETWORK; PEER-TO-PEER NETWORK COMMUNICATIONS ARCHITECTURE:

Basically all the above names refer to a network with no centralized servers. Network users can independently initiate communications sessions at their discretion in order to share resources with others on the network. Communications tasks are assigned so that data transmission between logical groups or layers in a Network is accomplished between entities in the same layer of the Open System Interconnection (OSI).

PEER-TO-PEER RESOURCE SHARING:

A system architecture that allows any station to contribute resources to the network while still running local application programs

PEM:

Privacy Enhanced Mail: Internet e-mail that provides confidentiality, authentication, and message integrity using various encryption methods.

PENATRATION:

Successful, repeatable, unauthorized access to a protected system resource

PERFORMANCE MANAGEMENT:

One of five categories of network management defined by ISO for management of OSI networks: Performance management subsystems are responsible for analyzing and controlling network performance, including network throughput and error rates.

PERFORMANCE MONITORING:

The collection of data, on either a part-time or full-time basis, in order to determine the overall data transfer efficiency of a circuit.

PERFORATOR / REPERFORATOR:

A paper tape punch; Perforator: Initial (originating) tape punching for information transmittal; Re-perforator: Automatically punches a tape based on the received information from the line.

PERIGEE:

The position in a satellite's orbit when it is closest to the earth

PERIPHERAL COMPONENT INTERCONNECT (PCI):

A unit that provides high-speed automatically configured interconnections between the cards in a PC (Personal Computer) motherboard, the system memory, and the CPU (Central Processing Unit).

PERIPHERAL DEVICE OR EQUIPMENT:

See Peripheral Devices

PERIPHERAL DEVICES:

Any devices that connect to a central or auxiliary computer would be referred to as Peripheral Devices. Such devices are generally connected to the computer through input/output (I/O) controller interfaces (Port). The controller is designed to handle speed differentials between the high-speed computer and the relatively lower speed of the device. Data transfers into and out of a peripheral device are also made through the I/O Controller. Examples of peripheral devices are, but not limited to Tape Stations (Magnetic Tape Drives), Rotating Memories (Drums and Hard Disks), Printers, and Video Monitors.

PERIPHERAL NODE:

In SNA: A node that uses local addresses and therefore is not affected by changes to network addresses. Peripheral nodes require boundary function assistance from an adjacent sub-area node.

PERL:

  Practical Extraction and Report Language: A programming language that is widely used for both simple, small tasks and for very large complex applications.
  During the 1990s it became the de-facto standard for creating CGI programs. Perl is known for providing many ways to accomplish the same task, with "there's more than one way to do it" being something of a motto in the Perl community.
  Because it is so easy to perform simple tasks in Perl it is often used by people with little or no formal programming training, and because Perl provides many sophisticated features it is often used by professionals for creating complex data-processing software, including the ‘server-side’ of large web sites. Perl does not provide significant support for creating programs with a graphical user interface.

PERMALINK:

A ‘permanent link’ to a particular posting in a blog: A permalink is a URI that points to a specific blog posting, rather than to the page in which the posting originally occurred (which may no longer contain the posting.)

PERMANENT CALLS:

Private line calls used for fixed point-to-point calls, for connections between PBXs (E&M to E&M), or for remote telephone extensions (FXO to FXS).

PERMANENT VIRTUAL CIRCUIT (PVC):

In data networking services, PVC refers to a circuit that is defined in a static manner, with static parameters, but is not tied to any physical path through the network.

PERMANENT VIRTUAL CIRCUIT INTERFACE PRIORITY QUEUING:

Interface-level priority queuing scheme in which prioritization is based on destination PVC rather than packet contents

PERMANENT VIRTUAL CONNECTION:

See Permanent Virtual Circuit

PERMISSION:

A rule associated with an object to regulate which users can gain access to the object and in what manner. Permissions are granted or denied by the objects owner.

PERSISTENT:

A LAN environment term describing a CSMA LAN where collision involved stations attempt immediate retransmission.

PERSONAL COMMUNICATIONS SERVICE (PCS):

1) Individualized telecommunications services permitting users to communicate from nearly any location. The low power, wireless communications technology uses lightweight, inexpensive pocket telephones and personal computers to transmit voice, fax, and data.

2) A designation used to describe a newer class of wireless communications services recently authorized by the FCC (Federal Communications Commission):  PCS systems use a different radio frequency (1.9 GHz band) than cellular phones and generally use all digital technology for transmission and reception.

PERSONAL COMPUTER (PC):

Any computing system used primarily by one person. Desktop, Lap or Home computer

PERSONAL COMPUTER MEMORY CARD INTERNATIONAL ASSOCIATION:

Standard used for credit-card-sized computer peripherals. Type I devices are very thin memory cards; type 2 devices include most MODEM(s) and interfaces; type 3 devices are used for disk drives and thicker components.

PERSONAL DIGITAL ASSISTANT (PDA):

A device that provides a personal carry-along database, calculator, alarm clock and personal communicator; It looks like a palmtop computer, and communications are accomplished through telephone lines or wireless.

P/F:

Poll/Final bit: Bit in bit-synchronous data link layer protocols that indicate the function of a frame. If the frame is a command, a 1 in this bit indicates a poll. If the frame is a response, a 1 in this bit indicates that the current frame is the last frame in the response.

PFS:

Perfect Forward Secrecy: Cryptographic characteristic associated with a derived shared secret value. With PFS, if one key is compromised, previous and subsequent keys are not compromised because subsequent keys are not derived from previous keys.

PG:

Peripheral Gateway: Computer and process within the ICM system that communicates directly with the ACD, PBX, or VRU at the call center. The PG reads status information from the peripheral and sends it to the Central Controller. In a private network configuration, the PG sends routing requests to the Central Controller and receives routing information in return.

PGL:

Peer Group Leader: In ATM, a node in a peer group that performs the functions of the LGN. Peer group leaders exchange PTSP(s) with peer nodes, in the parent peer group, to inform those nodes of the peer group's attributes and reach-ability, and to propagate information about the parent group and the parent group's parents to the nodes in the peer group.

PGM:

Pragmatic General Multicast: Reliable multicast transport protocol for multicast applications that require reliable, ordered, duplicate-free multicast data delivery from multiple sources to multiple receivers.

PGP:

Pretty Good Privacy: Considered the strongest program for encrypting data files and/or e-mail messages on Personal Computers (PC) and Macintosh computers. PGP includes authentication to verify the sender of a message and non-repudiation to prevent someone denying they sent a message.

PHASE:

The relative time position of a sine wave, the point at which the cycle advances

PHASE ALTERNATION LINE (PAL):

Video format used in most of Western Europe, Australia and others.

PHASE / DELAY EQUALIZER:

A corrected network where the phase delay remains substantially constant

PHASE HIT:

The unwanted shifting in the phase of an analog signal, specifically where the phase of a 1,004 Hz test signal shifts more than 20 degrees.

PHASE JITTER:

A lack of synchronization or other impairment caused by the mechanical or electrical changes in communications equipment

PHASE MODULATION (PM):

A phase shift modification of a sine wave for transmitting information, where the phase of the sine wave, or carrier, is modified in accordance with the information to be transmitted.

PHASE SHIFT:

Situation in which the relative position in time between the clock and data signals of a transmission becomes unsynchronized. In systems using long cables at higher transmission speeds, slight variances in cable construction, temperature, and other factors can cause a phase shift, resulting in high error rates.

PHASE SHIFT KEYING (PSK):

A modulation technique in which the phase of the carrier is modulated (shifted) based on the changing state of the input signal.

PHASED ARRAY:

Refers to an antenna that forms a beam by assigning different signal phases to a number of separate radiating elements

PHONE LINE NETWORKING:

Phone-line networking, may be referred to as Home-PNA, is based on the specifications developed by the Home Phone Networking Alliance (HPNA). The HPNA is a consortium of key networking technology companies that created a phone-line standard for the networking industry.  

PHOTODIODE:

A device: Detects optical (light) power and converts it to an electrical current/voltage.

PHP:

Hypertext Preprocessor: PHP is a programming language used almost exclusively for creating software that is part of a web site. The PHP language is designed to be intermingled with the HTML that is used to create web pages. Unlike HTML, the PHP code is read and processed by the web server software (HTML is read and processed by the web browser software.)

PHY:

1) Physical Sub-layer: One of two sub-layers of the FDDI physical layer.

2) Physical Layer: In ATM, the physical layer provides for the transmission of cells over a physical medium that connects two ATM devices.

3) See Physical Layer Protocol

PHYSICAL CONNECTION:

A physical link or connection - The full-duplex layer association between adjacent Physical Layer Protocols (PHY) in a Fiber Distributed Data Interface (FDDI) ring.

PHYSICAL CONNECTION MANAGEMENT (PCM):

The portion of a Fiber Distributed Data Interface (FDDI) that manages the physical connection between adjacent Physical Layer Protocols (PHY); This includes the connection signaling type, link confidence testing, and the enforcement of connection rules.

PHYSICAL CONTROL LAYER:

Layer 1 in the SNA architectural model: This layer is responsible for the physical specifications for the physical links between end systems.

PHYSICAL LAYER:

The lowest or bottom layer (layer 1) of the Open System Interconnection (OSI) model concerned with the mechanical (physical connectors) and electrical (currents, voltages, timing) and other related items, and also interfaces with the layer above, the link layer.

PHYSICAL LAYER INTERFACE MODULE:

Interface that allows AIP to a variety of physical layers, including TAXI and SONET multimode fiber-optic cable, SDH/SONET single-mode fiber cable, and E3 coaxial cable

PHYSICAL LAYER PROTOCOL (PHY):

A function of the Fiber Distributed Data Interface (FDDI) standard that defines symbols, line states, clocking requirements and the encoding of data for transmission.

PHYSICAL LINK:

A physical connection or link - The connection path, via the Physical Medium Dependent (PMD) and attached mediums, from the transmit function of one Physical Layer Protocol (PHY) entity to the receive function on an adjacent PHY entity in a ring.

PHYSICAL MEDIUM DEPENDENT (PMD):

A portion of the Fiber Distributed Data Interface (FDDI) standard: Defines the medium and protocols for transferring symbols between Physical Layer Protocols (PHY).

PHYSICAL PORT:

Input/output cards that support a number of physical communication ports; the ports can be configured for different types of frame relay interfaces and direct trunks.

PHYSICAL RECORD:

A block of data that would be transmitted between a peripheral device and a computer or between other devices, such as terminals

PHYSICAL TOPOLOGY:

The actual arrangement of lines, cables and hardware that make up a network. For example, bus, ring, or star.

PHYSICAL UNIT:

1) An input/output device and its associated recording medium such as tape units, disks, drums, card readers and printers.

2) In the IBM SNA environment, a physical unit is a component designed to manage and monitor the resources of a node.

PHYSNET:

Physics Network: Group of many DECnet-based physics research networks, including HEPnet

PIAFS:

Personal Handy-phone Internet Access Forum Standard: PHS Internet Access Forum Standard. ITU-T standard for support by ISDN of data terminal equipment with V-series type interfaces.

PIC:

1) Point in Call: Phases within a call. Examples of PIC are Answered, Long Duration, Released, etc. 2) Pre-subscribed Inter-exchange Carrier

PICO (p):

The prefix indicating one trillionth of a unit

PICOSECOND (Pico) (p):

One trillionth of a secon

PICS:

Platform for Internet Content Selection: A model for associating labels with content in header metadata, originally devised to help parents and teachers for controlling children's access to the internet.

PIGGYBACK:

1) To gain unauthorized access to a system via an authorized user's legitimate connection

2) Process of carrying acknowledgments within a data packet to save network bandwidth

PIGGYBACK ATTACK:  

Form of active wiretapping in which the attacker gains access to a system via intervals of inactivity in another user's legitimate communication connection. Sometimes referred to as a ‘between-the-lines’ attack.

PIM:

1) Peripheral Interface Manager: The Cisco proprietary interface between a peripheral and the Peripheral Gateway (PG)

2) Protocol Independent Multicast: Multicast routing architecture that allows the addition of IP multicast routing on existing IP networks. PIM is unicast routing protocol independent and can be operated in two modes: dense and sparse.

PIM DENSE MODE:

One of the two PIM operational modes: PIM dense mode is data-driven and resembles typical multicast routing protocols. Packets are forwarded on all outgoing interfaces until pruning and truncation occurs. In dense mode, receivers are densely populated, and it is assumed that the downstream networks want to receive and will probably use the data-grams that are forwarded to them. The cost of using dense mode is its default flooding behavior.

PIM SPARSE MODE:

One of the two PIM operational modes: PIM sparse mode tries to constrain data distribution so that a minimal number of routers in the network receive it. Packets are sent only if they are explicitly requested at the RP (Rendezvous Point). In sparse mode, receivers are widely distributed, and the assumption is that downstream networks will not necessarily use the data-grams that are sent to them. The cost of using sparse mode is its reliance on the periodic refreshing of explicit joint messages and its need for RP(s). Sometimes referred to as sparse mode PIM or PIM SM

PING:

Packet Internet Groper: A program useful in testing and debugging LAN/WAN troubles. It sends out an Internet Control Message sequence and expects a specified receiver to respond back in a specified time frame.

PING OF DEATH:

Attack that sends an improperly large ICMP (R0792) echo request packet (ping) with the intent of overflowing the input buffers of the destination machine and causing it to crash.

PING SWEEP:

Attack that sends ICMP (RFC 0792) echo requests (pings) to a range of IP addresses with the goal of finding hosts that can be probed for vulnerabilities

PING PONGING:

Phrase used to describe the actions of a packet in a two-node routing loop

PINX:

Private Integrated services Network Exchange: A PBX or key system which, in a BRI voice application, uses QSIG signaling.

PIT:

Plug-In Tester: A circuit card 'board' fault analyzer.

PIXEL:

Short for picture element: one spot in a rectilinear grid of thousands of such spots that form an image produced on the screen by a computer or on paper by a printer. A pixel is the smallest element that display or print hardware and software can manipulate to create letters, numbers, or graphics. A pixel is also called a pel.

PKCS:

Public-Key Cryptography Standards: Series of specifications published by RSA Laboratories for data structures and algorithm usage for basic applications of asymmetric cryptography.

PKCS #7:

Cryptographic Message Syntax Standard: It is a general syntax, developed and maintained by RSA Data Security, Inc., for data to which cryptography may be applied, such as digital signatures and encryption. It also provides syntax for disseminating certificates or certificate revocation lists.

PKCS #12:

Personal Information Exchange Syntax Standard: developed and maintained by RSA Data Security, Inc. This syntax standard specifies a portable format for storing or transporting a user’s private keys, certificates, and miscellaneous secrets.

PKI:

Public-Key Infrastructure: System of CA(s), optionally, RA(s) and other supporting servers and agents, that perform some set of certificate management, archive management, key management, and token management functions for a community of users in an application of asymmetric cryptography.

PKS:

See Public Key System

PL:

See Private Line

PLAR:

Private line, Automatic Ring-down: Leased voice circuit that connects two single endpoints together. When either telephone handset is taken off-hook, the remote telephone automatically rings.

PLAR-OPX:

PLAR Off-Premises eXtension connection: Using this option, the local voice port provides a local response before the remote voice port receives an answer. On FXO interfaces, the voice port will not answer until the remote side answers.

PLAIN OLD TELEPHONE SERVICE (POTS):

Refers to the basic service provided by a public telephone network, without any added facilities such as conditioning.

PLAINTEXT:

Data that is not encrypted; sometime also called clear text.

Data that is input to and transformed by an encryption process, or is output by a decryption process.

PLAN 2A/2B through PLAN 20:

Perforated tape Message Switching Systems:

Replacement of the ‘torn tape’ message handling process began in the late 1930’s. Western union developed switching systems (2A/2B through Plan 20) that allowed the operators to use a 9-conductor patch cord for cross-office connections. This 9-conductor cord allowed the character bits to be transmitted cross-office in parallel and were used in conjunction with a built in patch panel.

PLAN 21:

A Western Union semi-automatic perforated tape message switching Center:

Messages were received on a paper tape Printer/Perforator that punched and printed on ‘chadless’ tape. Chadless tape implied that the holes punched in the tape did not result in the hole remains (chad) being scattered all over the equipment or floor. When the holes were punched in the tape only three quarters of the hole was punched which resulted in the chad being retained or connected to the tape by a small section of chad. This allowed the transmitter mechanical pins to penetrate the holes in the tape and read the tape because the chad was pivoted up, but still connected to the paper tape.

PLAN 51:

  Semi-automatic perforated tape Switching Center: With patch cord facilities, push-button panels and relay switching matrices, which allowed rapid switching of messages.

All messages received (input) at the center were via a paper tape printer-perforator (punch), which created a printed and punched paper tape based on the message content. The printer-perforator punched and printed message information on ‘chadless’ tape.

  The Baudot (or similar) code set was used for all messages. Since the Baudot code did not have Start of Message (SOM) or End of Message (EOM) symbols it was necessary to use a sequence of characters for those purposes. Common usage was ‘ZCZC’ for the SOM and ‘NNNN’ for the EOM. When a complete message was received (at the center), EOM present, the message could be routed to its destination, based on the routing indicator(s).

PLAN 55:

  Automatic perforated tape Switching Center:

The Plan 55, Store and Forward, Automatic Message Switching System was designed and manufactured by W. U. for the Department of Defense for installation and operation at various locations around the world. Primarily these installations occurred on U. S. Air force Bases.

  The Plan 55 System was a pre-computer automatic message switching system that utilized paper tape perforators (punches), paper tape transmitters, many electrical-mechanical relays and controls, a vacuum tube matrix for reading addresses and other information, and a patchable director unit. The punched paper tape was the memory storage and history media.

  All inputs to, and outputs from the switching center, utilized the Baudot Code Set (modified). This was a five-bit code, with added start and stop bits. All tributaries operated at individually assigned speeds between 50 and 100 Words Per Minute (WPM) and used mechanical Teletype (teletypewriter) type of equipment. There was also a trunk line(s) connection between the various switching centers. The printer-perforator punched and printed message information on ‘chadless’ tape.

  Since the Baudot code did not have Start of Message (SOM) or End of Message (EOM) symbols it was necessary to use a sequence of characters for those purposes. Common usage was ‘ZCZC’ for the SOM and ‘NNNN’ for the EOM. When a complete message was received (at the center), EOM present, the message could be routed to its destination, based on the routing indicator(s).

PLAN 111A:

Partial Torn Tape message switching system:

A modernized torn tape system designed and manufactured in the early 1950s for small companies with limited budgets. The basic idea behind this system was to eliminate the costly push button and relay switching equipment or automatic center equipment and return to the torn tape concept, with some basic refinements. In this system it was not always necessary to tear the perforated tape off the perforator and hand carry it to a cross aisle send position because in many instances the receiving and sending equipment was located together in one console (unit).

PLANT:

Centrally housed equipment and line facilities installed and operated for the purpose of providing a communications medium. Physical property of the Telephone Company used for communications.

PLASMA DISPLAY:

A type of flat, visual display used instead of a cathode-ray tube (CRT) for terminal devices

PLCP:

Physical Layer Convergence Procedure: Specification that maps ATM cells into physical media, such as T3 or E3, and defines certain management information.

PLD:

Program Load Disc: A disc containing program (software) information.

PLESIOCHRONOUS TRANSMISSION:

Term describing digital signals that are sourced from different clocks of comparable accuracy and stability

PLIM:

Physical Layer Interface Module: Interface that allows the AIP (ATM Interface Processor) to service a variety of physical layers, including TAXI and SONET multimode fiber-optic cable, SDH / SONET single-mode fiber cable, and E3 coaxial cable.

PLM:

See Pulse Length Modulation

PLMN:

Public Land Mobile Network: Generic name for all mobile wireless networks that use earth-based stations rather than satellites. PLMN is the mobile equivalent of the PSTN.

PLN:

Packet Line: An inter-switch trunk designed to carry packets between IPX nodes.

PL/1:

Programming Language 1: An IBM developed general purpose programming language.

PLOTTER:

A type of computer non-impact printer often used to ‘draw’ graphic designs; any device used to draw charts, diagrams, and other line-based graphics.

PLOTTER FONT:

A font created by a series of dots connected by lines. Plotter fonts can be scaled to any size and are most often printed on plotters. Some dot-matrix printers also support plotter fonts.

PLP:

Packet Level Protocol: Network layer protocol in the X.25 protocol stack; sometimes called X.25 Level 3 and X.25 Protocol.

PLSP:

PNNI link State Packets

PLT:

Program Load Tape: A magnetic tape containing program information.

PLU:

Primary Logical Unit: The LU that is initiating a session with another LU.

PLUG AND PLAY:

A set of specifications developed by Intel that allows a computer to automatically detect and configure a device and install the appropriate device drivers.

PLUG-IN:

A piece of software incorporated into a larger piece of software that adds features to the larger piece of software.

PM:

1) Preventive Maintenance: A scheduled maintenance activity performed to reduce failures. Repair or check before failures occurred. See Phase Modulation

2) Performance Monitoring: Provides a variety of automatic functions to aid in the maintenance and operation of the network. PM is continuous, in-service monitoring of transmission quality that uses software-provision-able performance parameters. Performance parameters are measured for all four layers of the SONET signal: physical, section, line, and STS path.

PMD:

1) Polarization Mode Dispersion: An inherent property of all optical media caused by the difference in the propagation velocities of light in the transmission medium.

2) See Physical Medium Dependent

PMI:

Preventive Maintenance Inspection

PMO:

Program Management Office: The office in the DoD responsible for establishing and maintaining an aggressive DMS deployment program.

PNG:

A graphics format specifically designed for use on the World Wide Web. PNG allows the compression of images without any loss of quality, including high-resolution images

PNNI:

1) Private Network-Network Interface: ATM Forum specification for distributing topology information between switches and clusters of switches that are used to compute paths through the network. The specification is based on well-known link-state routing techniques and includes a mechanism for automatic configuration in networks in which the address structure reflects the topology.

2) Private Network Node Interface: ATM Forum specification for signaling to establish point-to-point and point-to-multipoint connections across an ATM network. The protocol is based on the ATM Forum UNI specification with additional mechanisms for source routing, crank-back, and alternate routing of call setup requests.

PODCASTING / POD-CASTING:

A form of audio broadcasting using the Internet: Pod-casting takes its name from a combination of ‘iPod’ and broadcasting. iPod is the popular digital audio player made by Apple computer, but pod-casting does not actually require the use of an iPod.
Pod-casting involves making one or more audio files available as ‘enclosures’ in an RSS feed. A pod-caster creates a list of music, and/or other sound files, such as recorded poetry, or ‘talk radio’ material, and makes that list available in the RSS 2.0 format. This list can then be obtained by people using various pod-cast ‘retriever’ software and in turn make these audio files available to digital audio devices.

POINT-TO-MULTIPOINT CIRCUIT:

A circuit that connects a single node or terminal to a multi-terminal line or switch

POINT-TO-POINT:

A private (private line), direct connection established for data transmission between two stations (terminals).

POINT-TO-POINT CONNECTION:

1) An uninterrupted direct link (line) between two pieces of equipment; could be a leased line or private line.

2) In ATM, a point-to-multipoint connection is a unidirectional connection in which a single source end-system (root node) connects to multiple destination end-systems (leaves). Also in ATM, a point-to-point connection can be a unidirectional or bidirectional connection between two ATM end-systems.

POINT-TO-POINT NETWORK:

A network configuration that interconnects two points (lines) together via a mechanical and/or electrical switching matrix or through a computerized system. The connection can be dedicated or switched and multiple connections may be established simultaneously, such as in the Circuit Switching Unit (CSU), Telex, TWX, Telephone, and Broadband Exchange or via a point to point transmission in Packet Switching networks.

POINT-TO-POINT PROTOCOL (PPP):

The Internet standard method for transmitting Internet Protocol (IP) packets over serial point-to-point links. PPP supports both asynchronous and synchronous lines, and can configure connections to a remote network dynamically, and ensure that the link is usable. PPP is documented in RFC 1661.

POINT TO POINT PROTOCOL OVER ETHERNET: (PPPoE):

A specification for connecting users on an Ethernet network to the Internet through a broadband connection: Such as a single DSL line, wireless device, or cable MODEM. Using PPPoE and a broadband MODEM, LAN (Local Area Network) users can gain individual authenticated access to high-speed data networks. By combining Ethernet and Point-to-Point Protocol (PPP), PPPoE provides an efficient way to create a separate connection for each user to a remote server.

POINT TO POINT TUNNELING PROTOCOL (PPTP):

Networking technology that supports multi-protocol Virtual Private Networks (VPN): enables remote users to access corporate networks securely across the Internet or other networks by dialing into an Internet Service Provider (ISP) or by connecting directly to the Internet. The Point-to-Point Tunneling Protocol (PPTP) tunnels, or encompasses, IP, IPX, or NetBEUI traffic inside of IP packets. This means that users can remotely run applications that are dependent upon particular network protocols. See PPTP

Note: IP: Internet Protocol; IPX: Integrated Packet Exchange; NetBEUI: NetBIOS Extended User Interface

POINT OF PRESENCE (POP):

The physical location or the junction between an inter-LATA common carrier and the intra-LATA common carrier: See POP.

POINT OF SALE:

A type of data transaction terminal used in retail sales

POISON REVERSE UPDATES:  

Routing updates that explicitly indicate that a network or a 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.

POL:

Provisioning Object Library

POLAR:

A binary bit stream in which all one bits are the same voltage polarity (either positive or negative) and all zero bits will be the opposite polarity, alternating polarities.

POLAR RETURN-TO-ZERO:

A polar signal with a 50 percent duty cycle, only the positive or negative pulse is used, not both

POLAR TRANSMISSION:

A method of transmitting teletypewriter signals (digital), where the marking bit is represented by a direct current flowing in one direction (positive) and the spacing bit is equally represented by a current flowing in the opposite direction (negative); Positive and Negative pulses.

POLICY:

The mechanism by which desktop settings are configured automatically: Defined by the administrator or any defined rule that determines the use of resources within the network. A policy can be based on a user, a device, a sub-network, a network, or an application.

POLICY DECISION POINT:

Server that makes policy decisions: It has global knowledge of network policies, and is consulted by network devices (like routers) that enforce the policies.

POLICY ENFORCEMENT POINT:

Device on which policy decisions are carried out: Usually a network node like a router or a switch.

POLICY ROUTING:

Routing scheme that forwards packets to specific interfaces based on user-configured policies. Such policies might specify that traffic sent from a particular network should be forwarded on one interface, and all other traffic should be forwarded on another interface.

POLICY SERVER:

At least one server in each QoS domain that holds policies for reference by client routers and switches and is used for decisions over client routers and switches

POLL / POLLING:

1) Past: The process of asking each terminal, in sequence, on a multipoint line if they wish to transmit (poll) or are ready to receive (call): an electrical, mechanical or control character action. The communications device or computer queries each terminal by transmitting a message (control characters) that the terminal can acknowledge by indicating its need for service. If a negative response to the polling is received from a terminal the polling continues with the next terminal in sequence until all terminals on the polling list are queried. Normally only one terminal at a time can be active, sending or receiving.

2) Present: Access method in which a primary network device inquires, in an orderly fashion, whether secondary devices have data to transmit. The inquiry occurs in the form of a message to each secondary that gives the secondary the right to transmit.

POLLING DELAY:

The predetermined time interval at which a device is polled by the master computer or control device

POLLING LIST:

A system station polling list used to determined which stations (terminals) will be polled and in what order. A line (station) polling list may also be used to determine polling priority.

POLOPHONIC RINGTONES:

Phones that play polyphonic ring-tones have the ability to produce 16 separate sounds at once. This provides music that is much richer and the tunes sound more like the music.

POLYMORPHIC VIRUS:

Polymorphic viruses create varied (fully functional) copies of themselves as a way to avoid detection from anti-virus software. Some polymorphic virus use different encryption schemes and requires different decryption routines. Thus, the same virus may look completely different on different systems or even within different files. Other polymorphic viruses vary instruction sequences and use false commands in the attempt to thwart anti-virus software. One of the most advanced polymorphic viruses uses a mutation-engine and random-number generators to change the virus code and its decryption routine.

POM:

1) Program Objective Memorandum

2) Provisioning Object Manager

PONY:

A local circuit not having a direct connection to a communications center or network: Sometimes used for maintenance testing or operational functions.

POP:

Point of Presence

1) The physical interface connection between a local exchange carrier and the main network.

2) The point to which the communications company terminates a subscriber's circuit for long distance service or leased line communications

3) The consolidation point in a local calling area where traffic is routed to an Internet Service Provider (ISP).

4) In OSS, a physical location where an inter-exchange carrier installed equipment to interconnect with a local exchange carrier (LEC).

5) Post Office Protocol. Protocol that client e-mail applications use to retrieve mail from a mail server.

POP3:

Post Office Protocol, level 3: An Internet Email Protocol providing for the delivery of messages between sender and receiver. POP 3 is the receiving server for the e-mail client (user).

PORT:

1) A network entry or exit point; a connection between a computer and an external device such as a printer port; a connection point for a multiplexer; the entrance or access point to a computer, multiplexer, device or network where signals may be supplied, extracted or observed.

2) On the Internet ‘port’ often refers to a number that is part of a URL (Universal Resource Locator), 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 numbers and Web servers would 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.

3) Interface on an internetworking device (such as a router).

4) To rewrite software or microcode so that it runs on a different hardware platform or in a different software environment than that for which it was originally designed.

PORT ADDRESS TRANSLATION:

Translation method that allows the user to conserve addresses in the global address pool by allowing source ports in TCP connections or UDP conversations to be translated. Different local addresses then map to the same global address, with port translation providing the necessary uniqueness.

PORT CONCENTRATOR:

A device that allows several terminals to share a single computer port

PORT SCAN:

Attack that sends client requests to a range of server port addresses on a host with the goal of finding an active port and exploiting a known vulnerability of that service.

PORT SELECTOR:

An electronic switch designed to furnish connectivity between different computer devices

PORT SHARING DEVICE:

A digital device physically located at the Front End Processor (FEP) end of the line that helps to extend the circuit capacity of a FEP by treating several point-to-point lines as if they were a single multipoint line.

PORTAL:

1) A device that allows unlike (translation required) systems to communicate over a common network link.

2) May be used to describe a Web site that is or intended to be the first place people see when using the Web. Typically a Portal site has a catalog of web sites, a search engine, or both. A Portal site may also offer E-mail and other service to entice people to use that site as their main ‘point of entry’ to the Web.

PORTWARE:

Software running on a MICA technology HMM or DMM

POSI:

Promoting conference for OSI: Group of executives from the six major Japanese computer manufacturers and Nippon Telephone and Telegraph that sets policies and commits resources to promote OSI

POSIX:

An acronym identifying the connecting interface to the UNIX operating system

POST:

Power-On Self Test: Set of hardware diagnostics that runs on a hardware device when that device is first powered up.

POSTCRIPT:

A Page Description Language (PDL): Developed by Adobe Systems for printing on laser printers. PostScript offers flexible font capability and high-quality graphics. It is the standard for desktop publishing because it is supported by image-setters, the high-resolution printers used by printing services for commercial typesetting.

POSTSCRIPT FONTS:

  Fonts that are defined in terms of the PostScript Page Description Language (PDL) rules and are intended to be printed on a PostScript compatible printer. When a document displayed in a screen font is sent to a PostScript printer, the printer uses the PostScript version if the font exists.

  If the font doesn't exist but a version is installed on the computer, that font is downloaded to the printer. If there is no PostScript font installed in either the printer or the computer, the bit-mapped (raster) font is translated into PostScript and the printer produces text using the bit-mapped font.

  PostScript fonts are distinguished from bit-mapped fonts by their smoothness, detail, and faithfulness to standards of quality established in the typographic industry.

POSTSCRIPT PRINTER:

A printer that uses the PostScript Page Description Language (PDL) to create text and graphics on the output medium, such as paper or overhead transparency. Examples of PostScript printers include the Apple LaserWriter, the NEC LC-890, and the QMS PS-810.

POST OFFICE PROTOCOL (POP):

An E-mail protocol that allows users to access e-mail using a graphical format mail program. The mail program (client) connects to the mail server only to transfer messages.

POSTING:

A single message entered into a network communications system.
POTS:

Plain Old Telephone Service

POTS DIAL PEER:  

Dial peer connected via a traditional telephony network: POTS peers point to a particular voice port on a voice network device.

POTS SPLITTER:

A device, which may be part of a larger device, that enables both a DSL data device, for example, a Cisco 1400 series router, and a standard analog device (telephone) to share the same ADSL line.

POWER LINE CARRIER:

A technique using a radio frequency carrier transmitted over the AC circuit in a building.

POWER-ON SERVICING:

Feature that allows faulty components to be diagnosed, removed, and replaced while the rest of the device continues to operate normally

POWER SCHEME:

A group of preset power management options. For example: a user can set elapsed times for putting the computer on standby and for turning off the monitor and hard disk. These settings are saved as a named power scheme.

PPM:

See Pulse Position Modulation 

PPP:

  Point-to-Point Protocol: A protocol for converting a Dial-up Connection to a point-to-point connection over the Internet. Frequently used for accessing the World Wide Web over telephone lines

  Successor to SLIP that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. Where SLIP was designed to work with IP; PPP was designed to work with several network layer protocols, such as IP, IPX, and ARA. PPP also has built-in security mechanisms, such as CHAP and PAP. PPP relies on two protocols: LCP and NCP.

PPPoE:
Point to Point Protocol over Ethernet: Software that works with a NIC to simulate a dial-up session and allows dynamic IP address assignment.

PPS:

Packet per Second

PPTP:

Point-to-Point Tunneling Protocol: A Linux, FreeBSD, NetBSD and OpenBSD client for the proprietary Microsoft Point-to-Point Tunneling Protocol. PPTP allows connection to a PPTP based Virtual Private Network (VPN) as used by employers and some cable and ADSL (Asymmetric Digital Subscriber Line) internet service providers. See Point-to-Point Tunneling Protocol.

PQ:

Priority Queuing

PQ/CBWFQ:

Priority queuing / Class-Based Weighted Fair Queuing: Feature that brings strict priority queuing to CBWFQ. Strict priority queuing allows delay-sensitive data, such as voice, to be de-queued and sent first before packets in other queues are de-queued, giving delay-sensitive data preferential treatment over other traffic.

PRA:

See Primary Rate Access

PRBS:

See Pseudo Random Binary Pulse Sequence

PRECEDENCE:

See Priority or Priority Indicators

PRECEDENCE ORDER:

Determines which value of an option is applied to a cable MODEM. Options defined in the most specific option set take precedence over the same options defined in more general sets. Within an option set, common options always have a lower precedence order than a specific service option if the cable MODEM has an associated service package. If a service package is not associated with the cable MODEM, the Trivial File Transfer Protocol (TFTP) server uses the common options.

PRECLONING:

Cloning a specified number of virtual access interfaces from a virtual template at system startup or when the command is configured.

PREEMPTION:

An interruption of a lower priority call or message in order to use the same circuit to transmit a higher priority message

PRESENTATION LAYER:

The sixth layer of the Open Systems Interconnection (OSI) model of data communications. It controls the formats of screens and files. Control codes, special graphics, and character sets work in this layer.

This layer ensures that information sent by the application layer of one system will be readable by the application layer of another. The presentation layer also is concerned with the data structures used by programs and therefore negotiates data transfer syntax for the application layer.

PRESENTATION SERVICES LAYER:

Layer 6 of the SNA architectural model: This layer provides network resource management, session presentation services, and some application management.

PRESET TO CALLBACK:

A form of security in which a remote access server verifies users by calling them back at numbers supplied by the network administrator at the time user privileges are granted. Only a network administrator can change a preset callback number. This ensures that no one can borrow a user's password and connect to the server from a location other than the user's normal location.

PRE-SHARED KEY:

Shared secret key that is used during IKE authentication

PREVENTIVE MAINTENANCE:

Planned periodic inspection, cleaning, adjustments and repairs in order to prevent system malfunctions

PRI:

Primary Rate Interface: An Integrated Services Digital Network (ISDN) interface typically used by larger customers. This interface consists of a single 64 Kbps Data (or ‘D’) channel plus 23 or 30 Bearer (or ‘B’) channels for voice and/or data; also known as Primary Rate Access, or PRA.

PRIMARY AREA:

A customer's local telephone calling area.

PRIMARY BLOCK:

See Primary Group

 PRIMARY DISK:

The hard disk drive that contains the system and boot partitions used to start Windows.

PRIMARY GROUP:

A group of basic signals (data patterns) that are combined through a multiplexing function, also may be referred to as the lowest level of the multiplexing hierarchy.

PRIMARY INTEREXCHANGE CARRIER (PIC):

The IEC designated by a customer to provide inter-LATA service automatically when the customer dials 1+ an area code and number.

PRIMARY MOUSE BUTTON:

The button used most often for clicking and double-clicking: The primary mouse button is the left button on most mice and trackball devices, and the lower button on some trackball devices, but a user can switch the function of the buttons by using the Mouse Properties dialog box in Control Panel.

PRIMARY PARTITION:

A type of partition that a user can create on basic disks: A primary partition is a portion of a physical disk that functions as though it were a physically separate disk. On basic Master Boot Record (MBR) disks, a user can create up to four primary partitions on a basic disk, or three primary partitions and an extended partition with multiple logical drives. On basic GPT disks, a user can create up to 128 primary partitions. Primary partitions are also known as volumes.

PRIMARY PATH:

The preferred switched route between two nodes or terminals

PRIMARY RATE ACCESS (PRA):

An Integrated Services Digital Network (ISDN) access method using maximum data rates of 2.048 Mbps in Europe, or 1.544 Mbps in the US and Japan.

PRIMARY RATE INTERFACE (PRI):

An Integrated Services Digital Network (ISDN) circuit transmitting at T1 or DS-1 speed: Provides the equivalent of 24 voice-grade channels. The ‘D’ channel is used for signaling (controls), leaving 23 ‘B’ channels for data and voice communications.

PRIMARY RING:

One of the two rings that make up a FDDI or CDDI ring: The primary ring is the default path for data transmissions.

PRIMARY ROUTING POINT:

The switch designated as the control point for a long distance telephone call.

PRIMARY STATION:

1) A station responsible for controlling a group data link; it controls one or more secondary stations.

2) In bit-synchronous data link layer protocols, such as HDLC and SDLC, a station that controls the transmission activity of secondary stations and performs other management functions, such as error control through polling or other means. Primary stations send commands to secondary stations and receive responses.

PRIMARY STORAGE:

Usually refers to the memory of a computer, Example: Delay Line, Film, Core, Crystal, Solid State, etc.

PRINT JOB:

The source code that contains both the data to be printed and the commands for print: Print jobs are classified into data types based on what modifications, if any, the spooler must make in order for the job to print correctly.

PRINT PROCESSOR:

The component working in conjunction with the printers driver, receives and alters print jobs, as necessary, according to their data type to ensure that the jobs print correctly.

PRINT QUEUE:

A print queue is a list of documents waiting to be printed on the printer. The print queue provides information such as the size of the document, document originator, and status information for printing.

PRINT SERVER:

A computer that is dedicated to managing the printers on a network: The print server can be any computer on the network; a computer and/or program which provides Local Area Network (LAN) users with access to a centralized printer; print jobs are usually handled in the order received (FIFO).

PRINT SPOOLER:

Software that accepts a document sent to a printer and then stores it on disk or in memory until the printer is ready for it. This collection of Dynamic Link Libraries (DLL) receives, processes, schedules, and distributes documents for printing. The term spooler is an acronym created from Simultaneous Print Operations on Line.

PRINT SPOOLER RESOURCE:

Printer queues providing access to a network printer connected to the network by an IP (Internet Protocol) address rather than by an individual name. Print spoolers are supported as cluster resources by a Resource DLL (Dynamic Link Libraries).

PRINTER:

A device that puts text or images on paper or other print media: Examples are laser printers or dot-matrix printers.

PRINTER CONTROL LANGUAGE (PCL):

The Page Description Language (PDL) developed by Hewlett Packard for their laser and inkjet printers. Because of the widespread use of laser printers, this command language has become a standard in many printers.

PRINTER CONVERTER:

A device used to allow an asynchronous printer to emulate an IBM 3287 synchronous printer, also known as a coaxial converter.

PRINTER DRIVER:

A program designed to allow other programs to work with a particular printer without concern for the specifics of the printer hardware and internal language. By using printer drivers that handle the uniqueness of each printer, programs can communicate properly with a variety of printers.

PRINTER FONTS:

Fonts residing in or intended for a printer: A printer font, usually located in the printers read-only memory (ROM), can be internal, downloaded, or on a font cartridge.

PRINTER JOB LANGUAGE (PJL):

The printer command language developed by Hewlett Packard that provides printer control at the print-job level. Using PJL commands, a user can change default printer settings such as number of copies to print. PJL commands also permit switching printer languages between print jobs without action by the user. If bi-directional communication is supported, a PJL-compatible printer can send information such as printer model and job status to the print server.

PRINTER PERFORATOR:

A paper tape perforator, that prints the characters (information) on the tape as it is being punched. Usually the printed character appears several holes in time after the actual punched character.

PRINTER PERMISSIONS:

Permissions that specify the type of access that a user or group has to a printer. The printer permissions are Print, Manage Printers, and Manage Documents.

PRINTER WINDOW:

Also called the queue view, the Printer window shows information about any pending print jobs for the printer. For each printer a user has installed or connected, the user can view and change such information as to how many documents are waiting to be printed, who owns them, and how large they are.

PRINTERS AND FAXES:

The folder in Control Panel that contains the Add Printer Wizard and icons for all the printers installed on the computer.

PRINTING POOL:

Two or more identical printers that are connected to one print server and act as a single printer. In this case, when a user prints a document, the print job will be sent to the first available printer in the pool.

PRIORITY:

The ranking of precedence or importance; priority indicators are contained in message headers. See Priority Indicators.

PRIORITY INDICATORS:

A code (character group) in a message header that determines transmission priority: such as urgent, rush, routine, or deferred.

PRIORITY QUEUE:

Routing feature in which frames in an output queue are prioritized based on various characteristics, such as packet size and interface type.

PRIVATE AUTOMATIC BRANCH EXCHANGE (PABX):

A small local telephone switch, in which users must dial 9 to access a local line

PRIVATE AUTOMATIC EXCHANGE:

See PABX or PBX

PRIVATE BRANCH EXCHANGE (PBX):
A private telephone switch that provides a full set of switching features for an office or campus. A PBX often uses digital-line protocols, although some are analog-based.

PRIVATE CABLE MODEM:

Each subscriber / account pair is associated with a single cable MODEM, which services one or more CPE(s) also associated with the subscriber / account

PRIVATE KEY:

The secret half of a cryptographic key pair that is used with a public key algorithm: Private keys are typically used to decrypt a symmetric session key, digitally sign data, or decrypt data that has been encrypted with the corresponding public key.

PRIVATE LINE (PL):

A telephone system that uses dedicated circuits to connect a customer's equipment at both ends of the line; a leased communications path assigned for the private use of one customer and having no connection to the public telephone system. A private line normally does not provide any carrier switching capability.

PRIVATE LINE SERVICE (PLS):

A dedicated telecommunications service provided to customers with high volume or special requirements. PLS falls under FCC regulation, and in most cases, would involve lines connected directly or indirectly (via a PBX) to the public switched telephone network

PRIVATE NETWORK:

An exclusive use communications network: Established and operated by an individual, business or organization. Private networks are usually made up of private lines and possibly some Private Branch Exchange (PBX) switching.

PRIVATE USE NETWORK:

Two or more restricted use private lines (channels) contracted by a customer and restricted for use by that customer only.

PRIVILEGE:

A user's right to perform a specific task, usually one that affects an entire computer system rather than a particular object. Privileges are assigned by administrators to individual users or groups of users as part of the security settings for the computer.

PRIVILEGE LEVEL:

A form of priority or user-level security in Packet switched networks; one of three settings: user, administration or guest is assigned for each user account.

PRIVILEGED PROCESS:

Computer process that is authorized and trusted to perform some security-relevant functions that ordinary processes may not perform.

PRL:

Preferred Roaming List: A database in a CDMA (Code Division Multiple Access) based wireless phone that tells it how to find and connect to locally available wireless network(s). The function of the PRL is most important when a phone is outside its home network and must seek out an alternate network. The PRL in a phone can be periodically updated to account for changes in wireless networks that the phone may encounter.

PRMD:

Private Management Domain: X.400 Message Handling System private organization mail system; example, NASA-mail.

PROBE:

Probe is an intrusive analysis technique that uses the information obtained during scanning to more fully interrogate each network device. The probe uses well known techniques to fully confirm any suspected device vulnerability, as well as detect any vulnerability that cannot be found using non-intrusive techniques.

PROCESSING DELAY:

In data communications, the time taken by a computer to operate on an inbound message and return a response

PROCESS SWITCHING:

Operation that provides full route evaluation and per-packet load balancing across parallel WAN links: Involves the transmission of entire frames to the router CPU, where they are repackaged for delivery to or from a WAN interface, with the router making a route selection for each packet. Process switching is the most resource-intensive switching operation that the CPU can perform.

PROFILE:

A term used in packet-switched environments to describe a set of parameters or values defining a hardware device (printer, terminal) that would be stored and later recalled as a group for later use.

PROGRAM:

The specific sequence of computational steps in a programming language; a set of instructions for a computer to perform

PROGRAM CIRCUIT:

A voice grade circuit (channel) which has been equalized (conditioned) to handle a wider range of frequencies than what ordinary voice signals require.

PROGRAM FLOWCHARTING:

See Flowchart

PROGRAM INFECTOR:

A program infector virus infects other program files once an infected application is executed and the activated virus is loaded into memory.

PROGRAMMABLE READ ONLY MEMORY (PROM):

Nonvolatile memory: Programmed by the equipment manufacturer. PROM can be modified (re-programmed) with special equipment that erases the previous program. It is unaffected by power loss.

PROGRAMMABLE TERMINAL:

A computer terminal that contains memory and has processor capability: Also known as an intelligent terminal.

PROGRAMMER, APPLICATION:

The individual responsible for writing or maintaining application programs

PROGRAMMER, SYSTEM:

The individual(s) responsible for writing or maintaining operating systems or programs that have to do with translation, loading, supervision, maintenance, control, running of computers and computer programs. On small, special-purpose or limited-purpose computers the distinction between application programmer and system programmer is not always obvious, and often they may be the same individual.

PROM:

See Programmable Read Only Memory

PROPAGATION DELAY:

The time it takes for a signal to travel between two points on the network; greater the distance and equipment involved, greater the delay. Propagation delay is useful in determining the response time of a device to a signal. 

PROPRIETARY:

Refers to information (property) that is owned by an individual or an organization that is restricted for use by other entities

PROTECTED CHECKSUM:

Checksum that is computed for a data object that protects against active attacks that attempt to change the checksum value to make it correlate with illegal changes made to the data object

PROTECTED DISTRIBUTION SYSTEM:

Wire-line or fiber-optic system that includes sufficient safeguards, acoustic, electrical, electromagnetic, and physical, to permit its use for unencrypted transmission of clear text data.

 PROTECTION RING:

One of a hierarchy of privileged operation modes of a system that gives certain access rights to processes authorized to operate in that mode.

PROTOCOL:

A set of procedures used between equipment such as terminals (stations) and computers to permit communication and exchange of data between them.

Formal description of a set of rules and conventions that govern how devices on a network exchange information

PROTOCOL ADDRESS:

Network Address: Network layer address referring to a logical, rather than a physical, network device.

PROTOCOL ANALYZER:

A device or software application, that allows a user to analyze the performance of the network and data to ensure that the network is operating within the specified parameters.

PROTOCOL CONVERTER:

A node that connects otherwise incompatible networks: Converts (translates) data codes and transmission protocols to enable interoperability.

PROTOCOL DATA UNIT (PDU):

Information delivered as a unit between similar entities that may contain control information, address information, data from a Service Data Unit (SDU) at a higher layer, or any combination of those three data types.

PROTOCOL FILTERING:

A bridge feature: Can be programmed to always forward or always reject specific protocol signals that may be contained in data transmissions.

PROTOCOL INDEPENDENT ROUTER:

A routing device that provides the same functions as protocol specific routers, such as Transmission Control Protocol/Internet Protocol (TCP/IP) or DECnet routers, but functions independent of protocols.

PROTOCOL STACK:

Set of related communications protocols that operate together and, as a group, address communication at some or all of the seven layers of the OSI reference model. Not every protocol stack covers each layer of the model, and often a single protocol in the stack addresses a number of layers at once. TCP/IP is a typical protocol stack.

PROTOCOL SUITE:

Complementary collection of communication protocols used in a computer network

PROTOCOL TRANSLATOR:

Network device or software that converts one protocol into another similar protocol

PROTOCOL VITAL SIGNS (PVS):

A systematic method of analysis and display of protocol operational parameters: To determine the cause of system performance degradation.

PROVIDER EDGE ROUTER:

Router that is part of a service provider's network and is connected to a Customer Edge (CE) router

PROVISIONING:

Creation of an active subscriber account, or modification of parameters for an existing subscriber account: Provisioning of a subscriber account includes subscriber account registration and device activation.

PROXY:

1) Entity that, in the interest of efficiency, essentially stands in for another entity.

2) Special gateways that relay one H.323 session to another.

PROXY ADDRESS RESOLUTION PROTOCOL:

See PROXY ARP

PROXY ARP:

Proxy Address Resolution Protocol: Variation of the ARP protocol in which an intermediate device (router) sends an ARP response on behalf of an end node to the requesting host. Proxy ARP can lessen bandwidth use on slow-speed WAN links.

PROXY EXPLORER:

Technique that minimizes exploding explorer packet traffic through a SRB network by creating an explorer packet reply cache, the entries of which are reused when subsequent explorer packets need to find the same host.

PROXY POLLING:

Technique that alleviates the load across a SDLC network by allowing routers to act as proxies for primary and secondary nodes, thus keeping polling traffic off of the shared links; Proxy polling has been replaced by SDLC Transport.

PROXY SERVER:

Intermediary program that acts as both a server and a client for the purpose of making requests on behalf of other clients: Requests are serviced internally or by passing them on, possibly after translation, to other servers. A proxy interprets, and if necessary, rewrites a request message before forwarding it.

A Proxy Server sits in between a Client (user) and the real (main) Server that the Client uses. Clients are sometimes configured to use a Proxy Server and the client makes all requests to the Proxy Server, which then makes requests to the ‘real’ server and passes the result back to the Client. Sometimes the Proxy server will store the results and give a stored result instead of making a new request. This reduces the use of a Network.

PSD:

Port Sharing Devices: Used in conjunction with terminal servers

PSDN:

Packet Switched Digital Network

PSDS:

See Public Switched Digital Service

PSE:

Packet Switch Exchange: The acronym PSE generally is used in reference to a switch in an X.25 packet switch.

PSEUDO CHANNEL:

An internal ASC dummy or ‘pseudo’ Channel: Allows a message generated by the communications computer to be processed as if it were received from or to be transmitted to a terminal. This message could also be read or written to a storage device, such as a magnetic disc or magnetic tape. Pseudo channels are also used for operator printouts, message retrieval or delivery of a message to temporary storage for future delivery.

PSEUDO RANDOM BINARY PULSE SEQUENCE (PRBS):

A random data test pattern generated in such a manner that another circuit, operating independently, can synchronize on the pattern and detect transmission bit errors.

PSEUDO RANDOM NOISE MODULATION:

A communications technique in which each digital bit is chopped into chips that are phase-shifted in a random pattern by codes to stimulate noise. The chip pattern can be re-phased by matched filter techniques.

PSK:

See Phase-Shift Keying

PSN:

Packet Switched Network: Network that uses packet-switching technology for data transfer; sometimes called a PSDN. See Public Switched Network

PSS:

Packet Switched Service
PSTN:
See Public Switched Telephone Network

PTF:

Patch and Test Facility: Technical Control circuit testing and switching media

PTI:

Payload Type Identifier: 3-bit descriptor in the ATM cell header indicating the type of payload that the cell contains. Payload types include user and management cells; one combination indicates that the cell is the last cell of an AAL5 frame.

PTSE:

PNNI Topology State Element: Collection of PNNI information that is flooded among all logical nodes within a peer group.

PTSP:

PNNI Topology State Packet: Type of PNNI routing packet used to exchange reachable and resource information among ATM switches to ensure that a connection request is routed to the destination along a path that has a high probability of meeting the requested QoS. Typically, PTSP(s) include bidirectional information about the transit behavior of particular nodes (entry and exit ports) and the current internal state.

PTT:

Postal, Telephone, and Telegraph: Government agency that provides telephone services. PTT(s) exist in most areas outside North America (Europe) and provide both local and long-distance telephone services.

p2mp:

Point-to-Multipoint: Communication between a series of receivers and transmitters to a central location. Cisco p2mp typically is set up in three segments to enable frequency re-use.

p2p:

Point-to-Point: Communication between one receiver and one location. P2p has a higher bandwidth than p2mp because it has less overhead to manage; there is only one receiver per transmitter.

P2P:

Peer to Peer

PU:

Physical Unit: SNA component that manages and monitors the resources of a node, as requested by a SSCP. There is one PU per node.

PU 2:

Physical Unit 2: SNA peripheral node that can support only DLU(s) that require services from a VTAM host and that are capable of only performing the secondary LU role in SNA sessions.

PU 2.1:

Physical Unit type 2.1: SNA network node used for connecting peer nodes in a peer-oriented network. PU 2.1 sessions do not require that one node reside on VTAM. APPN is based upon PU 2.1 nodes, which also can be connected to a traditional hierarchical SNA network.

 PU 4:

Physical Unit 4: Component of an IBM FEP capable of full-duplex data transfer. Each SNA device employs a separate data and control path into transmit and receive buffers of the control program.

PU 5:

Physical Unit 5: Component of an IBM mainframe or host computer that manages a SNA network. PU 5 nodes are involved in routing within the SNA path control layer.

PUA:

Profile User Agent

PUBLIC:

Indicates for the customer(s) use; a common carrier provided service.

PUBLIC ACCESS LINE (PAL):

A shared-resource data network: Offers data communications services to public subscribers. See Packet Switching.

PUBLIC DIAL PORT:

A dial in port which provides access to a system or service, such as a packet network, from a terminal connected to the public telephone network.

PUBLIC KEY:

Publicly available component of a pair of cryptographic keys used for asymmetric cryptography

See PKCS (Public-Key Cryptography Standards)

PUBLIC KEY CERTIFICATE:

Digital certificate that binds a system entity's identity to a public key value, and possibly to additional data items

PUBLIC KEY CRYPTOGRAPHY:

A method of cryptography in which two different keys are used: a public key for encrypting data and a private key for decrypting data. Public key cryptography is also called asymmetric

PUBLIC KEY SYSTEM (PKS):

A two key encryption algorithm that transforms data from plain text to cipher text with one key that is made public, and converts cipher text back to plain text with a different key that remains secret.

PUBLIC SERVICE COMMISSION (PSC):

An agency responsible for the regulation of telecommunications services: Also known as the Public Utilities Commission (PUC) in many areas.

PUBLIC SWITCHED DIGITAL SERVICE (PSDS):

A user timed and/or leased service that provides alternate voice and data on a 2-wire loop.

PUBLIC SWITCHED NETWORK (PSN):

Any public switching system that provides point to point circuit switching: In the US, there are basically four: Telex, Teletypewriter Exchange (TWX), telephone, and the broadband exchange.

PUBLIC SWITCHED TELEPHONE NETWORK (PSTN):

The Voice Telephone network available to anyone, worldwide, with a telephone and/or access privileges

PUBLIC UTILITIES COMMISSION (PUC):

An agency that regulates intrastate telecommunications and telephone service

PUC:

See Public Utilities Commission

PULSE:

A sharp change in the current or voltage on a circuit; digital direct current (DC) using positive or negative pulses. Usually the width (time duration) of the pulse is determined from the bit per second (bps) rate. The Pulse could also be used to operate an electrical switch or relay.

PULSE AMPLITUDE MODULATION (PAM):

A form of modulation in which the carrier's modulated amplitude varies according to the characteristics of the original analog signal; the pulse width is constant.

PULSE CODE:

A pulse train (flow) formatted to represent information or digital (binary) code.

PULSE CODE MODULATION (PCM):

The process of sampling and coding a modulating (modulated) signal and transforming each element of information into various pulses and spaces.

PULSE DENSITY:

Ones Density: Scheme that allows a CSU/DSU to reliably recover the data clock: 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.

PULSE DURATION MODULATION (PDM):

A form of modulation in which the duration of the pulses (pulse width) vary.

PULSE LENGTH MODULATION (PLM):

A form of carrier modulation where the pulse length is varied

PULSE-LINK REPEATER:

Connects two E&M signaling circuits back to back, changing the E of one circuit to the M of the other and vice versa.

PULSE MODULATION:

The transmission of information modulated by a pulsed or intermittent carrier: Pulse width, count, position, phase, and/or amplitude can be the varied characteristic.

PULSE POSITION MODULATION (PPM):

Pulse modulation achieved by varying the timing of the pulses, while maintaining their duration.

PULSE WIDTH MODULATION (PWM):

A method of modulating a signal, in which the duration of a pulse width is varied according to the characteristic of the modulating signal.

PUP:

Protocol similar to IP developed at PARC; See Parc Universal Packet

PUSH:

The technology that puts pre-selected content directly on your computer screen from the Internet without your need to browse for it. With this technology the desktop can be programmed, for example, to automatically receive such things as local weather, news headlines, selected stock reports, and sports scores for selected teams or events.

PUSH DOWN QUEUE:

A method of prioritizing a list of items waiting to be processed where the last item added to the list is the first item processed. Last in, first out (LIFO)

PUSH BUTTON DIALING:

A method of generating a sequence of digits to establish a circuit connection by using a number pad rather than a rotary dial, Referred to as Touch-Tone dialing.

PUSH UP QUEUE:

A method of prioritizing a list of items waiting to be processed where the first item added to the list is the first item processed. First in, first out (FIFO)

PVC:

Permanent Virtual Circuit: The PDN equivalent of a private line. A fixed virtual circuit used in a packet-switched environment between two users, requiring no call establishment. In ATM terminology, called a Permanent Virtual Connection.

PVP:

Permanent Virtual Path: Virtual path that consists of PVC(s).

PVP TUNNELING:

Permanent Virtual Path Tunneling: Method of linking two private ATM networks across a public network using a virtual path. The public network transparently trunks the entire collection of virtual channels in the virtual path between the two private networks.

PVS:

See Protocol Vital Signs

PVST+:

Per-VLAN Spanning Tree +: Support for Dot1q trunks to map multiple spanning trees to a single spanning tree

PWM:

See Pulse Width Modulation