[About This Glossary]


A packet is a unit of information processed by the Network Layer of the OSI model. The packet header contains the logical (network) address of the destination node. Intermediate nodes forward a packet until it reaches its destination. A packet can contain an entire message generated by higher OSI layers, or a segment of a much larger message.

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.

Packet Telephony
Packet telephony is voice telephone service provided over connectionless packet networks, instead of the public-switched telephone service.

Packet Transfer Mode (PTM)
PTM is a type of data communication that is not synchronized by a clock. Data is broken into variable-size units of data, and those packets are relayed from one node to another, often in multiple parallel paths, until they reach their final destination.

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

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

Payback Period
The time it will take for cost savings or increased profits from a new system to exceed the original investment required to create the system is referred to as the payback period.

Personal Computer Memory Card International Association (PCMCIA)
The PCMCIA slot in a laptop was designed for PC memory expansion. NICs and modems can attach to a laptop through the PCMCIA slot.

A phase is a description of one wave's position relative to another at a particular point in time. Phase differences are measured in degrees from 0 to 180.

Priority Queue
The priority queue is a segment of a split's/skill's queue from which calls are taken first.

Private Branch Exchange (PBX)
PBX is a sophisticated business telephone system that provides all the switches features of a telephone company's CO switch. Today's PBXs are fully digital, not only offering very sophisticated voice services, such as voice messaging, but also intergrating voice and data.

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.

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."

Peripheral Component Interconnect (PCI) Bus
PCI bus is a newer 64-bit local bus technology for PCs. A bus connects the central processor of a PC with the video controller, disk controller, hard drives, and memory.

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.

Permanent Virtual Circuit (PVC)
A PVC is a connection across a frame relay network, or cell-switching network such as ATM. A PVC behaves like a dedicated line between source and destination end-points. When activated, a PVC will always establish a path between these two end points.

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.

Physical Medium-Dependent Sublayer
The physical medium-dependent sublayer is the lower sublayer of the ATM protocol stack's Physical Layer. This layer supports functions, such as bit timing and line coding, that vary according to the type of transmission medium selected.

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.

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 of Presence (POP)
POP is the physical transfer point between two networks. In most cases, the POP is a CO switch located in the same building as the LEC CO.

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.

There are two primary ways the term "port" is used in networking. Port can refer to a physical connection point in a device, such as a port on a switch or multiplexer. Port can also refer to a number that identifies a software process within a computer. "Well-known" ports in TCP architecture are examples of the second type of port.

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

Port Usage Rate (PUR)
The number of PBX ports required to process a call. PUR is typically twice the Call Usage Rate (CUR), since a simple call requires a minimum of two ports (input and output). See "Call Usage Rate (CUR).

Poisson is the traffic engineering formula that determines the number of trunks required to serve a particular volume of call traffic at a given grade of service. Poisson assumes all blocked calls immediately redial, and keep redialing until they get through. The formula is named for S.D. Poisson, who first developed the mathematical approach in the 1820s; it is also called the Molina formula.

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 is a sophisticated business telephone system that provides all the switching features of a telephone company's CO switch. Today's PBXs are fully digital, not only offering very sophisticated voice services, such as voice messaging, but also integrating voice and data.

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

Private Signaling System Number 1 (Q.SIG, or PSS1)
An ISO standard that defines the ISDN signaling and control methods used to link PBXs in private ISDN networks. The standard extends the "Q" point in the ISDN logical reference model, which was established by the ITU-T in its Q.93x series of recommendations that defined the basic functions of ISDN switching systems. QSIG signaling allows certain ISDN features to work in a single-vendor or multi-vendor network.

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.

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.

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.

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

The process of allocating transmission lines, switching capacity, and central programming to provide telecommunications service to a customer is referred to as provisioning.

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.

Pulse Code Modulation (PCM)
PCM is a method of converting an analog voice signal to a digital signal that can be translated accurately back into a voice signal after transmission. A codec samples the voice signal 8,000 times per second, then converts each sample to a binary number that expresses the amplitude and frequency of the sample in a very compact form. These binary numbers are then transmitted to the destination. The receiving codec reverses the process, using the stream of binary numbers to recreate the original analog wave form of the voice.

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


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.

See "Private Signaling System Number 1."

Quality of Service (QoS), Type of Service (ToS)
Users of the Transport Layer specify QoS or ToS parameters as part of a request for a communication channel. The QoS parameters define different levels of service based on the requirements of an application. For example, an interactive application that needs good response time would specify high QoS values for connection establishment delay, throughput, transit delay, and connection priority. However, a file transfer application needs reliable, error-free data transfer more than it needs a prompt connection, thus it would request high QoS parameters for residual error rate/probability.

The first-come, first-served line-up of incoming calls awaiting an available line or agent is referred to as the queue.

A queue is a collection point where calls are held until an agent or attendant can answer them. Calls are ordered as they arrive and are served in that order. Depending on the time delay in answering a call, announcements, music, or prepared messages may be employed until the call is answered.

Queue Directory Number (QDN)
QDN is an associated extension number of a split. It is not normally dialed to reach a split. The split can be accessed by dialing the QDN. The QDN is also referred to as a split group extension.