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N - P

Network interface card (NIC)
Often abbreviated as NIC, an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.

Newsgroup
An on-line discussion group.
On the Internet, there are literally thousands of newsgroups covering every conceivable interest.To view and post messages to a newsgroup, you need a news reader, a program that runs on your computer and connects you to a news server on the Internet.

PCMCIA
Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards.

Ping
Short for Packet Internet Groper, 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.

POP
Short for Post Office Protocol, a protocol used for email service.

Port
An interface on a computer to which you can connect a device. Personal computers have various types of ports. In TCP/IP and UDP networks, an endpoint to a logical connection. The port number identifies what type of port it is. For example, port 80 is used for HTTP traffic.

Protocol
An agreed-upon format for transmitting data between two devices.
The protocol determines the following:

  • the type of error checking to be used
  • data compression method, if any
  • how the sending device will indicate that it has finished sending a message
  • how the receiving device will indicate that it has received a message

There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example,
some are simpler than others, some are more reliable, and some are faster.
From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers. The protocol can be implemented either in hardware or in software.

Proxy Server
A server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.

Proxy servers have two main purposes:

  • Improve Performance
    Proxy servers can dramatically improve performance for groups of users. This is because it saves the results of all requests for a certain amount of time. Consider the case where both user X and user Y access the World Wide Web through a proxy server. First user X requests a certain Web page, which we'll call Page 1. Sometime later, user Y requests the same page. Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X. Since the proxy server is often on the same network as the user, this is a much faster operation. Real proxy servers support hundreds or thousands of users. The major online services such as Compuserve and America Online, for example, employ an array of proxy servers.
  • Filter Requests
    Proxy servers can also be used to filter requests. For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.