A piece of a message transmitted over a packet-switching network. One of the key features of a packet is that it contains the destination address in addition to the data. In IP networks, packets are often called datagrams.

Packet Switching refers to protocols in which messages are divided into packets before they are sent. Each packet is then transmitted individually and can even follow different routes to its destination.

PAP (Password Authentication Protocol) is the most basic form of authentication, in which a user's name and password are transmitted over a network and compared to a table of name-password pairs.

The main weakness of PAP is that both the username and password are transmitted "in the clear" -- that is, in an unencrypted form. Contrast with CHAP. For more information, please refer to this page http://www.networksorcery.com/enp/protocol/pap.htm.

The PCMCIA (Personal Computer Memory Card International Association) is an industry group organized in 1989 to promote standards for a credit card-size memory or I/O device that would fit into a personal computer, usually a notebook or laptop computer.

Ping is a utility to determine whether a specific IP address is accessible. It works by sending a packet to the specified address and waiting for a reply. PING is used primarily to troubleshoot Internet connections. There are many freeware and shareware Ping utilities available for personal computers.

A point-of-presence (POP) is an access point to the Internet. A POP necessarily has a unique Internet Protocol (IP) address. Your Internet service provider (ISP) or online service provider (such as AOL) has a point-of-presence on the Internet

POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. For more information, please refer to this page http://www.networksorcery.com/enp/protocol/pop.htm

A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server. The port numbers are divided into three ranges: the Well Known Ports, the Registered Ports, and the Dynamic and/or Private Ports. For more information, please refer to this web page http://www.iana.org/assignments/port-numbers

POTS is a term sometimes used in discussion of new telephone technologies in which the question of whether and how existing voice transmission for ordinary phone communication can be accommodated

PPPoE (Point-to-Point Protocol over Ethernet) is a specification for connecting the users on an Ethernet to the Internet through a common broadband medium, such as a single DSL line, wireless device or cable modem. All the users over the Ethernet share a common connection. PPPoE can be used to have an office or building-full of users share a common Digital Subscriber Line (DSL), cable modem, or wireless connection to the Internet. PPPoE combines the Point-to-Point Protocol (PPP), commonly used in dialup connections, with the Ethernet protocol, which supports multiple users in a local area network.For more information, please refer to this page http://www.networksorcery.com/enp/protocol/ppp.htm.

Protocol is the special set of rules that end points in a telecommunication connection use when they communicate. For more information, please refer to this page http://www.networksorcery.com/enp/Protocol.htm

Proxy Server is a server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service.

PSTN (public switched telephone network) is the world's collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. It's also referred to as the Plain Old Telephone Service (POTS).