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Packet

The basic unit of information sent over a network. Each packet contains the destination address, the sender’s address, error-control information, and data. The size and format of a packet depend on the protocol being used.

Page

A document, or collection of information, available over the World Wide Web. A page can contain text, graphics, video, and sound files. Also, a portion of memory that the virtual memory manager can swap to and from a hard disk.

Paging

A virtual memory operation in which pages are transferred from memory to disk when memory becomes full. When a thread accesses a page that’s not in memory, a page fault occurs and the memory manager uses page tables to find the page on disk and then loads the page into memory.

Partition

A portion of a memory device that behaves as if it were a physically separate unit.

Ping

A network management utility that checks to see whether another computer is available and functioning. It sends a short message to which the other computer automatically responds. If the other computer doesn’t respond to the ping, you usually can’t establish communications.

Point of presence (POP)

A physical site in a geographic area where a network access provider, such as a telecommunications company, has equipment to which users connect. The local telephone company’s central office in a particular area is also sometimes referred to as their POP for that area.

Point-to-Point Tunneling Protocol (PPTP)

A protocol that provides router-to-router and host-to-network connections over a telephone line (or a network link that acts like a telephone line). See Serial Line Internet Protocol (SLIP).

Post Office Protocol (POP)

A protocol by which a mail server on the Internet lets you access your e-mail and download it to a PC or Macintosh. Most people refer to this protocol with its version number (POP2, POP3, and so on) to avoid confusing it with points of presence (POPs).

Primary partition

A portion of the hard disk that’s been marked as a potentially bootable logical drive by an operating system. MS-DOS can support only a single primary partition. Master boot record disks can support four primary partitions. Computers with the Intel Itanium processor use a GUID partition table that supports up to 128 primary partitions.

Profile

Loaded by the system when a user logs on, the profile defines a user’s environment, including network settings, printer connections, desktop settings, and program items.

Protected Extensible Authentication Protocol (PEAP)

A protocol developed jointly by Microsoft, RSA Security, and Cisco for transmitting authentication data, including passwords, over 802.11 wireless networks.

Protocol

A set of rules for transferring data between two devices.

Proxy server

A server that receives Web requests from clients, retrieves Web pages, and forwards them to clients. Proxy servers can dramatically improve performance for groups of users by caching retrieved pages. Proxy servers also provide security by shielding the IP addresses of internal clients.

Public-key cryptography

A method of secure transmission in which two different keys are used—a public key for encrypting data and a private key for decrypting data.

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