Packet
A chunk of data sent over a network.
Packet Switched Network
Networks that transfer packets of data. Packets are broken down into an efficient size for routing, each carrying its own number and the Internet address for which it is destined.
Packet-filtering firewall
A firewall technology that looks at packets of data going over a network and checks them against a routing table before permitting or denying them access.
Parallel computing
A computer processing architecture that allows several processors, which all have their own memory, to work simultaneously.
Parallel Processing
The practice of completing a task with several processors that share memory and work simultaneously.
Personal communications service (PCS)
Combining three different technologies, this advanced network architecture provides wireless networking mobility. A PCS phone can connect to a PC for wireless networking.
Personal Communications Services (PCS)
A mobile phone service that sends calls from transmitter to transmitter, using its own network and offering more coverage than cellular networks.
Personal digital assistant (PDA)
A hand-held computer that combines computing, telephone/fax and networking features and can also have cell phone, fax sender and personal organizer features.
Platform for Privacy Preferences (P3P)
A project of the World Wide Web Consortium that will give consumers a way to learn about and react to the way websites may be using personal information.
Plug-in
Any small piece of software that adds extra functions to a larger piece of software.
POP
An acronym for both "Point of Presence" and "Post Office Protocol." Point of presence refers to a location that a network can be connected to (generally used to count the potential subscriber base of a cellular phone system), while post office protocol refers to the way in which e-mail software obtains mail from a mail server.
Port
An interface (connector) between the computer and the outside world. The number of ports on a communications controller or front-end processor determines the number of communications channels that can be connected to it. The number of ports on a computer determines the number of peripheral devices that can be attached to it.
Portal
A comprehensive web site that is designed to be the first site seen when a computer logs on to the web. Portal sites often have links to e-mail usage, a search engine or other features. Yahoo! and MSN.com are portals. Portals are aimed at broad audiences with common interests. (Also see "Hub.")
PPP (Point to Point Protocol)
Protocol that enables a computer to use the combination of a standard telephone line and modem to make TCP/IP connections.
Proxy firewall
This type of firewall offers security across networks by looking at content. Other security features, such as data encryption and authentication, can be added.
PTSN (Public Switched Telephone Network)
A term that represents the traditional telephone system.
Protocol
A set of rules for communicating between computers. The use of standard protocols allows products from different vendors to communicate on a common network.
Public Key Cryptography
A method of coding in which encryption and decryption are done with public and private keys, allowing users who don't know one another other to send secure or verifiable messages.
Public Key Infrastructure
A system for securely exchanging information within a company, group or worldwide that includes a method for publishing the public keys used in public key cryptography and for tracking expired keys.
Pull
The traditional model of Web delivery by which a user's browser requests information before the server sends it.
Push
The model of Web delivery in which a server sends a user information without receiving a request for it.
