P

Packet
A packet is a unit of information that can be transmitted over a network. A packet is generated at the Network Layer of the OSI model protocol stack. Information contained in the header of a packet is sufficient to transmit the packet from the sending node to the receiving node, even when the packet must traverse intermediate nodes. A packet can be an entire message, or a segment of a much larger message generated at the Application Layer.

Packet Latency
The transmission delay created when a device processes a packet is referred to as the packet latency. It is the duration from the time a device reads the first byte of a packet, until the time it forwards that byte.

Packet Spoofing
Spoofing means that a router responds to a local host in lieu of sending information across a WAN link to a remote host. The local host thinks the response came from the remote host/network, when it really came from the router.

Packet-Switched Networks
Packet switching is what occurs as a packet is traveling from the source node to the destination node when there are intermediate nodes between source and destination. When the packet travels through the intermediate node (a packet switch), it must "switch" the packet to the next node in sequence.

Password Authentication Protocol (PAP)
PAP is a method to identify and authenticate PPP peers.

Parser
A program that reads and executes programming script written in a high-level language is referred to as a parser. See interpreter.

Peer
In networking terms, a peer is a device or process in one computer that has the same intelligence and functionality as a device or process in another computer.

Peer-to-Peer
Two programs or processes that use the same protocol to communicate and perform approximately the same function for their respective nodes are referred to as peer processes. With peer processes, in general, neither process controls the other, and the same protocol is used for data flowing in either direction. Communication between them is referred to as "peer-to-peer."

Peripherals
Peripherals are parts of a computer that are not on the primary board (mother board) of a computer system. Peripherals include hard drives, floppy drives, and modems.

Peripheral Component Interconnect (PCI)
PCI was introduced by Intel to define a local bus system for a computer. PCI allows up to 10 expansion cards to be installed in a computer.

Permanent Virtual Circuit (PVC)
PVC is one of two types of virtual circuits, the other is switched virtual circuits (SVCs). A PVC behaves like a dedicated line between source and destination endpoints. When activated, a PVC will always establish a path between these two endpoints. PVC is usually used in the context of a packet switching (or cell switching) network.

Personal Digital Assistant (PDA)
PDA devices are very small and provide a subset of the operations of a typical computer (PC). They are used for scheduling, electronic notepads, and small database applications.

Platform for Privacy Preferences (P3P)
P3P is an open specification for Web site privacy policies that can be automatically interpreted and understood by browsers. User-defined browser settings can then control the amount and type of information provided to a Web site.

Plenum
A plenum is a duct for building heating or air conditioning, often found above suspended ceiling tiles or in raised floors. "Plenum-grade" cable meets fire codes; the cable coating is fire-resistant, and does not emit toxic fumes when burned.

Plug-and-Play (PnP)
PnP is a standard that gives computers the ability to automatically recognize a newly installed device, without a complex process of user configuration.

Plug-In
A plug-in is a software module that adds a specific feature to a browser. For example, plug-ins provide support for particular file formats, such as Shockwave or RealAudio.

Point-to-Point
A network connects nodes, some of which are hosts to which terminal nodes attach, in two different ways: point-to-point and broadcast. Point-to-point networks fall into two classes: circuit-switched networks, in which a connection is formed between the nodes, as in a telephone network; and packet-switched or connectionless networks, in which packets of data, or datagrams, are passed from node to node until they reach their destination, like telegrams.

Point-to-Point Protocol (PPP)
PPP is an Internet standard communications protocol that offers support for multiple network protocols, data compression, host configuration, and link setup. PPP is based on the HDLC standard.

Point of Presence (POP)
POP refers to an ISP's Internet access node for a city or area code.

Port
There are two primary ways the term port is used in networking. The first refers to a physical port in a device, such as an input/output (I/O) port on a switch where cables are plugged into the device. Ports also relate to processes running on nodes connected to a network. If a machine is running multiple processes, each process must be uniquely identified to communicate. "Well known" ports in TCP architecture, such as FTP and HTTP are examples of this type of port.

Portable Operating System Interface for UNIX (POSIX)
POSIX is a set of standard operating system interfaces based on UNIX. This standard approach serves as a common denominator among several "flavors" of UNIX.

Port Mirroring
Port mirroring is the capability to send duplicate information out a selected port (mainly for monitoring purposes).

Practical Extraction and Report Language (Perl)
Perl is an interpreted programming language designed for processing text. Because of its strong text-handling features, Perl has become one of the most popular languages for writing server-side CGI scripts.

Pretty Good Privacy (PGP)
PGP is the most commonly used asymmetric encryption (the public-key method) for protecting messages across the Internet.

Print Server
A print server is a LAN-based computer that provides users on a network access to a printer. Multiple users, therefore, share the printer.

Private Branch Exchange (PBX)
A PBX can multiplex both voice and data onto T-carriers (T1, T3, etc.), and support both voice and data communications from one extension over a single pair of wires. Some PBXs can also be configured to provide a LAN capability in addition to voice and data service. Although such LANs typically operate at much slower bit rates than Ethernet or Token Ring, the integration of voice and data can provide savings in wiring cost.

Private Facilities
In the context of WANs, private facilities are those owned and maintained by an organization.

Process
A generalized series of events that occur during the life cycle of a development project is referred to as a process.

Promiscuous Mode
This mode is a setting that forces a NIC to process every frame it receives. The NIC in a network analyzer can be set to promiscuous mode.

Property
Properties are attributes of an object. They often represent nouns or adjectives. For example, one property of an object representing an e-mail might be Subject.

Proprietary
The term proprietary refers to a network solution designed and implemented using equipment and protocols specific to one vendor. Purchasing equipment from one vendor typically creates proprietary networks. The opposite of a proprietary network is an "open" network based on industry standards.

Protocol
A protocol in networking is the agreed upon method of communication between computer processes attached to a network.

Proxy Agent
A proxy agent is an SNMP agent that optimizes network management command traffic to critical managed elements, or translates proprietary device commands to and from SNMP command format.

Proxy Server
A proxy server is similar to a "middleman," and is often used as a firewall. A proxy server does not permit direct packet communication between an external and internal network.

Public Facilities
In the context of WANs, public facilities are those leased through a carrier, such as a telephone company or long distance service provider.

Public-Key (Asymmetric) Encryption
Public-key encryption is a cryptographic system that uses two mathematically related keys: one key is used to encrypt a message, and the other is used to decrypt it. People who need to receive encrypted messages distribute their public keys, but keep their private keys secret.

Python
Python is an interpreted, object-oriented programming language. Python interpreters are available for most operating systems.

Q

Q Bit
The Q bit is a bit in an X.25 packet that indicates whether or not a packet contains control information or user data.

Quality of Service (QoS)
QOS defines a type of service a communications link can provide. QoS often specifies factors such as delay, throughput, and error rate.