This Glossary is intended only to define some basic terms new Netizens are likely to encounter. There are other Dictionaries and Glossaries on the Web. Suggestions for additional links are welcome.

Anonymous FTP

Most public FTP servers allow anyone to log into the system as user anonymous. By convention, the user's email address is used as the password.


Common Gateway Interface. A computer program or script residing on a web server, following the standards of HTTP, that serves as an interface between the server and the web browser.


User-end software or computer designed to access and interact with a server.


Server software that is running in the background on a computer and is ready to accept incoming connections.

Default Gateway

The router assigned by the terminal server.


Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.


Domain Name Service. A DNS database cross-references a domain name, such as, and its associated hosts, with their IP addresses. A host's IP address, not necessarily the host and domain name, is needed to connect to a remote server.


The name for a network of computers. For example, is the domain name for any number of machines, or hosts, within AzNET's network. Any machine attached to that network, including all users' machines with a dialup connection, are hosts within the domain. Furthermore, is within the .com domain.


Plural of FAQ, Frequently Asked Question.


File Transfer Protocol. An established protocol to allow files to be transferred from one system to another.


A system designed to prevent unauthorized access to or from a private network or computer. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

There are several types of firewall techniques:

  • *Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
  • *Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.
  • *Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
  • *Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses. In practice, many firewalls use two or more of these techniques in concert.

A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.


See router.


The specific name of a machine residing within a domain. For example, www is the name of a machine inside the domain, its fully qualified host name being Please note that www does not necessarily specify a protocol. By convention, web servers are given the name www but any legal domain name will do. Furthermore, a server running web services may be running any number of other daemons, such as FTP and SMTP.


Hyper Text Markup Language. A suite of tags and a specialized syntax used for formatting a document and creating links to other documents for use on a HTTP server. HTML files usually have the extension .htm or .html. This document, for instance, was created using HTML.


Hyper Text Transfer Protocol. The basic protocol for the World Wide Web allowing for systems, documents and files to be linked together via URLs and other instructions given in an HTML document.


Internet Message Access Protocol. Allows an email client to access and manipulate a remote email file without downloading it to the local system.


A vast network of networks, subnets and computers using the TCP/IP suite of protocols. Internet is not a generic name for all internets (interconnected networks), as others may be based on other protocols. The word Internet, when referring to the world-wide TCP/IP-based network, is a proper noun and should be capitalized.


Internet Network Information Center. Among other things, the InterNIC is the central registry of all U.S. domain names, Domain Name Servers and IP addresses. A domain name lookup for a domain, such as, will return the names and addresses of the Domain Name Servers handling name services for the hosts in that domain.


Internet Protocol. See TCP/IP.

IP Address

A numerical address specified in four parts, separated by dots (periods) and each part having a number in the range of 0 to 255, the same range as for a byte. Each IP address, then, is four bytes long.

Every machine on the Internet must have an IP address. An example is's IP address of A machine, however, does not have to have a host or domain name.


Internet Service Provider. A company providing complete Internet access to the public, most often through modem connections. Virtually every Internet protocol and service is available in an open environment. This differs from Commercial Online Services, such as America Online, in that those services provide access to a closed network of computers running its own proprietary software. However, those companies are now providing Internet access, although content is sometimes restricted.

Name Server

See DNS.


Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.

NAT serves three main purposes:

Provides a type of firewall by hiding internal IP addresses Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations. Allows a company to combine multiple ISDN connections into a single Internet connection.




The stream of USENET news articles flowing into a news server from another news server. Newsfeeds are made by agreement between the administrators of news servers. Servers, such as, may have arrangements for multiple newsfeeds, as most servers do not carry all available USENET news groups. If one newsfeed goes down, some news groups will often continue to be received from a feed not affected by the particular outage.


See InterNIC.


Network News Transport Protocol. Allows for a news client or another news server to interact with a news server, usually on port 119.

Open Relay

An open relay is a mail server that accepts all messages, regardless of whether they are coming from authorized users of the server or are destined to users on that server, and attempts to deliver them to its ultimate destination. This was general Internet policy until fairly recently, when the abuse of open relays for the delivery of unsolicited commercial e-mail and denial-of-service attacks grew to unbearable levels. When a mail server is found to have an open relay, it will be listed on the RBL.


Post Office Protocol. A suite of commands, usually sent to port 110 (POP3) of a server allowing for the transfer of email from the server to the client (user's email software). These commands are issued by the email client, the whole process being transparent to the user.


Point to Point Protocol. The protocol used to allow two modems to transmit Internet traffic over phone lines. Considered to be more modern and efficient than SLIP.


Real Time Blackhole List Created by Mail Abuse Prevention System (MAPS) LLC., Realtime Blackhole List consists of IP addresses whose owners refuse to stop the proliferation of spam.

The RBL usually lists server IP addresses from ISPs whose customers are responsible for the spam and from ISPs whose servers are hijacked for spam relay.

As subscribers to the RBL, ISPs and companies will know from which IP addresses to block traffic. Most traffic blocking occurs during the SMTP connection phase. The receiving end will check the RBL for the connecting IP address. If the IP address matches one on the list, then the connection gets dropped before accepting any traffic from the spammer. Some ISPs, though, will choose to blackhole (or ignore) IP packets at their routers. The goal here is to block all IP traffic.

Those offenders who wish to be removed from the list must drop the spammer and strengthen their AUPs. If one can't change its AUP, but is willing to supply MAPS with the netblocks allocated to the spammer, MAPS can RBL the subnetblocks.

It is important to note that all e-mail and packet blocking is done by the recipient, not MAPS. MAPS is only responsible for bouncing spam that is directed at its servers.


A computer dedicated to the task of routing TCP/IP packets through the Internet. Simply told, routers act together as a relay system, each pointing to one or more routers upstream and downstream.


Used in reference to a machine and/or software (daemon) that provides services. Examples of such services are mail servers (usually running SMTP), news servers (running a NNTP daemon) and web servers (HTTP software).


Serial Line Internet Protocol. Allows Internet traffic to be conducted over serial lines.

Spam Filter

A set of rules that a mail server can be configured to use, to determine if an incoming email should be delivered to the intended recipient, or rejected/returned to the sender as a unsolicited message.


Simple Mail Transport Protocol. The protocol and suite of commands used to exchange email between two servers, usually running on port 25, or to transfer email from a client to a server.


Spam is unsolicited email (or news postings), often of a commercial nature and typically sent as part of a bulk mailing. If you didn't ask for it, sign up on a mailing list related to it, or leave your email address on a web form asking for more information on it, it's spam.


A subset of a network. For instance, AzNET owns subnets under the network, examples being, and, with each host (computer) on the subnet being assigned a number in the last octet. For example, the address ( is a machine in the subnet. IP addresses are hierarchical from right to left (from the specific to the general). Domain and host names are hierarchical from left to right, with the leftmost element being the specific host, then working up from one subdomain to the next.


A digital telecommunications link capable of carrying 1.544 million bits per second.


A digital telecommunications link capable of carrying 44.736 million bits per second.


Transport Control Protocol. See TCP/IP.


The underlying protocols and structure of the Internet. A method for carrying packets of digital data in a specific format. All Internet traffic must adhere to TCP/IP.


The most common of several methods of logging into a remote server, usually to port 23. A telnet session will run a shell (text-based interface) on the server and provide the user with a system prompt, as though the user were working directly on the machine.

It is possible to telnet to other ports of a server, each port running a service, and "converse" with the daemon in its language. Examples are port 80 for HTTP, port 25 for SMTP, port 21 for FTP and port 110 for POP3, each running software that will accept specific commands. For instance, telnet to port 80 of a machine known to run a web server and issue the command:


Terminal Server

A machine dedicated to the task of accepting dialup connections. Modems are directly attached to a terminal server, some of which are capable of having several dozen connections. Some terminal servers have modems built into them. When a customer connects to AzNET, they are connected directly to a terminal server, which verifies the username and password. The terminal server is, in turn, connected to a router, often sitting right next to it, which routes the TCP/IP packets to and from the user via the terminal server.


Universal Resource Locator. A specialized syntax for addressing another server or a document, in the form of protocol://host/directory-or-user/directory/.../filename



A term referring to the vast network of news servers running software compliant with NNTP. USENET is arranged in news groups, of which there are tens of thousands, each having any number of recent articles submitted by users in a "bulletin board" fashion. Only news reader software (and an Internet connection) is required to read and send USENET news.


Unix to Unix Copy. A series of utilities allowing for the transfer of files via a serial line.


Windows Sockets. A standard for MS Windows software allowing it to interact with TCP/IP and the Internet. Virtually all Internet software running under Windows must be Winsock compliant.


A shortened expression for World Wide Web.

Web Browser

A client software package used for accessing the World Wide Web. Examples include Netscape, Opera and Explorer

World Wide Web

An expression for all Internet protocols accessible via a web browser, HTTP being the most common. Other services, such as FTP, can be accessed with a software program (web browser) capable of exchanging commands of the particular protocol with the server and displaying the results to screen. The web, then, is an attempt to bring the most popular Internet protocols under one interface, as opposed to running individual FTP clients, for instance. Some web clients include complete email and news interfaces.


Acronym for World Wide Web.

visitors since 8 April 1999

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