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Internet The Internet is a vast worldwide network comprised of thousands of smaller interconnected networks; this worldwide network evolved from a project funded by the U.S. Defense Advanced Research Projects Agency (DARPA). The Internet was originally created to help researchers and scientists exchange information quickly and actually prohibited use of the network for commercial purposes. Today, the Internet has grown dramatically and its users have expanded from research institutions and scientific laboratories to commercial businesses and consumers. The Internet now includes many for-profit Internet Service Providers such as ATTIS. Along with the increase in number of users on the Internet, the quantity of tools that can be used on the Internet has also grown. Now these users on the Internet can not only transfer files in electronic format, they can send messages via electronic mail (e-mail), conduct research using the vast resources of the Internet, hold real-time "talk" sessions with others connected to the Internet, and much more. ATTIS receives its customers' network traffic and delivers it either to the destination address or, as needed, to a Global Service Provider who forwards it onto the ultimate destination. In turn, ATTIS receives network traffic that is destined for its customers from Global Service Providers and then delivers it to the appropriate location. The ATTIS network is composed of multiple network hubs connected by a high speed Internet backbone network. Each major network hub runs on an FDDI LAN connecting routers and hosts that accept and route Internet Protocol (IP) traffic and provide auxiliary services that make accessing the Internet easier. Today, customers access the ATTIS network by connecting to the closest major hub via point-to-point DS1 (T-1), DS3, Dedicated ISDN, Frame Relay or ATM Cell Relay. Each of these major hubs is connected directly to the Internet through an Internet Global Service Provider.

Domain Name Service (DNS) Domain Name Service (DNS), though typically invisible to the user, is the most fundamental tool associated with use of the Internet. The Internet uses the IP protocol and all IP traffic must have a source host address and a destination host address in the form of Unfortunately, these addresses are extremely cumbersome and nearly impossible to remember. The function of DNS is to map the required IP addresses into more user-friendly, easy-to-remember host names. For example, the IP address of the ATTIS mail server could be, but its associated host name is DNS allows users to document the correlation between their IP addresses and host names. Each site is responsible for documenting the correlation between their own IP addresses and host names. This information is then propagated to other DNS servers all over the world. Everyone on the Internet relies on this mapping to easily access hosts and resources. Also since hosts at a specific site are associated with a specific IP network address, all hosts at that site can be grouped together into a single domain. In this way, many Internet sites can reuse a host name such as "compass", as long as they each belong to different domains. To clarify, does not correspond to the same IP address as, since the domain "" is associated with the network and the domain "" is associated with the network. Of course, two computers cannot have the same host name if they are part of the same domain. One or more hosts running specialized software provide the DNS for a particular site; these hosts are commonly referred to as name servers or domain name servers. Customers are responsible for providing one primary name server at their location or they can choose to use ATTIS' optional Primary DNS service. As part of our basic service, ATTIS offers Dedicated Access customers the option of using one of our name servers as a primary or secondary name server, for one fully qualified domain per customer. There is no additional charge for secondary DNS and a nominal charge for primary DNS services. The advantage of such a configuration is that if the primary name server fails, the ATTIS name server can provide the required mapping between host names and IP addresses.

Without a secondary name server, the site would be virtually isolated from the rest of the Internet. Remote users would find hosts at that site to be unresponsive to their host names. Likewise, local users trying to reach any host would be forced to manually enter the destination IP address in place of its host name. Please note that not providing DNS is NOT a security feature; it will not prevent your site from receiving data since the IP addresses for your site can easily be found or guessed.

Electronic Mail System Electronic mail (e-mail) is an electronic equivalent to a letter delivered by the US Postal Service. However, in its electronic format, mail can be delivered almost instantaneously around the world! The Internet is equivalent to the US Postal Service delivery system and like the US Postal Service there must be a mechanism for getting mail in and out of the delivery system. With the US Postal Service, the sender must take the letter to the nearest post office or mailbox. Once a letter is delivered by the US Postal Service, the receiver must go to their mailbox and retrieve their mail. Similarly, the sender of e-mail must have a way of both delivering and receiving mail from the delivery system. This is accomplished through the use of individual host e-mail software, mail servers, and mail gateways. ATTIS Dedicated Access customers may provide their own e-mail solution or can choose to use one provided by ATTIS. We are proud to offer 30 complimentary email boxes for the dedicated customers domain name, hosted on our email servers. With this service they can both send and receive email using client based email programs such as Microsoft Outlook Express or Eudora, as well as utilize other features such as spam detection and web based email (Where you can login to a website to check your email from anywhere on the internet). Additional e-mail boxes are available for a nominal fee. This option is commonly chosen since it simplifies the administrative tasks for the customers by letting AT&T manage the email servers that hold their important email. Each host must have an e-mail software package installed to generate the actual e-mail messages. The host e-mail software must be configured to forward messages to the local SMTP mail server for delivery. The local SMTP mail server then determines where to send outgoing messages by looking up the Mail Exchange (MX) record for the top level domain portion of the destination e-mail address. For example, if the destination address of an electronic mail message is "[email protected]", the latter portion of the address is The SMTP mail server (which may also be referred to as the "mail server", "mail host", "mail spooler", or "mail relay") will check its DNS to obtain the MX record for The mail server would then forward the e-mail message to the IP address indicated in the MX record for The mail server also accepts incoming mail addressed to its site and delivers the mail to the individual hosts. The mail server may be configured to "spool" incoming mail if an individual host is temporarily unable to receive mail. The mail server stores the messages until the host is again able to accept mail. A spooling facility requires that disk space is reserved on the mail server for this purpose; the more mail a site gets, the more disk space is required. A reasonable configuration is enough disk space to spool mail for the entire site for three days. In some environments, a mail gateway is also necessary. A mail gateway's function is to translate e-mail messages from a proprietary format to a standard, SMTP-compliant format. For example, a mail gateway might translate between Macintosh Quickmail and SMTP Internet mail. If you are unsure which mail package your site is using, contact your local system administrator. If you need assistance setting up your e-mail system, you may contact your Internet Application Manager for a list of integration partners.

Network News Server

An electronic news feed provides access to the exchange of information between Usenet news servers around the world. The process of exchanging information between Usenet servers occurs fairly frequently in order that updates and postings to Usenet news groups can be propagated throughout the Internet. The function of Usenet news is to allow Internet users to exchange ideas about particular subjects ranging from highly technical to political to recreational. Many users find that Usenet news is a valuable resource since specific questions or ideas can be posted to a news group and a response is usually posted fairly rapidly. Internet users tend to monitor news groups that are of specific interest to them; therefore, the likelihood of getting valuable, free information is quite high. Since Usenet is not administered by any one entity, news groups may or may not be moderated. This means that some newsgroups may be considered distasteful, offensive, or inappropriate to certain users. ATTIS currently provides its customers an unrestricted Usenet news feed which consists of ALL of the newsgroups it receives. It is the customer's responsibility to filter out unwanted newsgroups. Customers who want to receive Usenet news must provide a high performance host that can devote a large percentage of resources to processing news. ATTIS recommends that dedicated access customers set up their news server on a host with the following minimal characteristics:

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Mid-size UNIX server, SUN Sparc 10 or equivalent 64 - 128 megabytes of RAM 1-5 gigabytes of disk storage Usenet news software must be installed and configured on the news server. InterNetNews (INN) is a free software package that is the defacto standard news server software. While there are other commercially available news software packages, SBIS recommends INN or Netscape News Server for its dedicated access customers. This recommendation may change in the near future with the advent of news server software incorporating Graphical User Interfaces (GUIs) that make configuration and administration of the news server much simpler. Each host also needs to have a newsreader installed. Most Web browsers provide a newsreader (see Web Browser below). Please note that the configuration and administration of a news server is a complicated issue, requiring a high level of systems administration expertise. ATTIS can refer you to one of our integration partners if you need assistance in setting up your news server.

Web Browser A Web browser, such as Netscape Navigator, is a software application that enables individual users to access the Internet with a Graphical User Interface (GUI). These applications make it easy for Internet users to do research, locate specific sites or services, and conduct financial transactions and keep up on the news available on the World Wide Web (www). Most Web browsers also provide facilities for posting and reading Usenet news. Under an agreement with Netscape Communications Corporation, ATTIS is authorized to sell Netscape Navigator LAN Edition.

Web Server More and more organizations are finding it valuable to have a presence on the World Wide Web (WWW). Web servers function as virtual storefronts to provide customer service, marketing, advertisements and public relations information to Internet users. Web servers may also be used to provide resources or proprietary information to employees or key partners. A Web server can be easily configured to record the number of hits or connections to each of its Web pages; this information can be used to measure the interest level of the content of the Web pages themselves. If you want to have a Web server on the Internet, SBIS recommends that your server have at least the following


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Mid-size UNIX server, SUN Sparc 5 or equivalent 32 megabytes of RAM 1-5 gigabits of disk storage If the load on the Web server is too great, additional servers may be set up to handle additional requests.

Packet Filters Packet filters are typically implemented on the routers connecting a site to the Internet. These filters are a set of criteria by which each IP packet, sent or received from a particular interface, is judged. If the packet meets the criteria, the router will process it. If the packet does not meet the criteria, the router will discard it. Since each IP packet has a source and destination address, it is possible to narrow down other Internet sites able to connect to your network. However, since most Internet applications require two-way transmission, such filtering will also decrease the number of sites your users are able to access. Along with a source and destination address, IP packets utilizing TCP and UDP protocols also contain a destination port number. The port number determines what Internet service this packet is accessing. For example, an IP packet with TCP port number 25 is destined for the Sendmail port, the standard SMTP mail port on a UNIX machine. Many sites choose to develop filter criteria based on the TCP port number and the structure of the packet itself. Such filtering is certainly more thorough than the simple source/address packet filter, however, it requires an in-depth understanding of TCP/IP. Finally, filters can be created based on the location of particular bits within each packet. Such filtering is quite valuable to those who have mastered the intricacies of TCP/IP.

ACL (Short for access control list) - A set of data that informs a computer's operating system which permissions, or access rights, that each user or group has to a specific system object, such as a directory or file. Each object has a unique security attribute that identifies which users have access to it, and the ACL is a list of each object and user access privileges such as read, write or execute. ADSL Asymmetric High Speed Internet) - A High Speed Internet (HSI) line where the upload speed is different from the download speed. Usually the download speed is much greater. Applet A small Java program that can be embedded in an HTML page. Applets differ from full-fledged Java applications in that they are not allowed to access certain resources on the local computer, such as files and serial devices (modems, printers, etc.), and are prohibited from communicating with most other computers across a network. The common rule is that an applet can only make an Internet connection to the computer from which the applet was sent. ARIN (Acronym for the American Registry for Internet Numbers) - ARIN, founded in 1997, is a non-profit organization that registers and administers IP numbers for North America, a portion of the Caribbean and sub-Saharan Africa. ARIN is one of four regional Internet registries. ARPANet (Advanced Research Projects Agency Network) - The precursor to the Internet. Developed in the late 60's and early 70's by the US Department of Defense as an experiment in wide-area-networking to connect together computers

that were each running different system so that people at one location could use computing resources from another location. AS (Autonomous System) An autonomous system (AS) is the unit of router policy, either a single network or a group of networks that is controlled by a common network administrator (or group of administrators) on behalf of an entity (such as a university, a business enterprise, or ISP). An autonomous system is also sometimes referred to as a routing domain. Each autonomous system is assigned a globally unique number called an Autonomous System Number (ASN). ATM (Short for Asynchronous Transfer Mode) - A network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with other technologies like FrameRelay or Ethernet. The small, constant cell size allows ATM equipment/nodes to transmit user data, video, audio, and over the same network, and assure that no single type of data saturates the line. backbone A high-speed line or series of connections that forms a major pathway within a network. The term is relative as a backbone in a small network will likely be much smaller than many non-backbone lines in a large network. AT&T has a national IP backbone with OC-192 lines. (OC-192=9.952 Gbps) Bandwidth How much information you can send through a connection. Usually measured in bits-per-second. A full page of English text is about 16,000 bits. A fast modem can move about 57,000 bits in one second. Full-motion full-screen video would require roughly 10,000,000 bits-per-second, depending on compression. Baud In common usage the baud rate of a modem is how many bits it can send or receive per second. Technically, baud is the number of times per second that the carrier signal shifts value - for example a 1200 bit-per-second modem actually runs at 300 baud, but it moves 4 bits per baud (4 x 300= 1200 bits per second). BGP (Short for Border Gateway Protocol) - A routing protocol that enables groups of routers (called autonomous systems) to share routing information so that efficient, loop-free routes can be established. BGP is commonly used within and between Internet Service Providers (ISPs). The protocol is defined in RFC 1771. Binary Information consisting entirely of ones and zeros. Also, commonly used to refer to files that are not simply text files, e.g. images. Bit (Binary DigIT) - A single digit number in base-2, in other words, either a 1 or a zero. The smallest unit of computerized data. Bandwidth is usually measured in bits-per-second. Boot To load the first piece of software that starts a computer. Because the operating system is essential for running all other programs, it is usually the first piece of software loaded during the boot process. Bps (Bits-Per-Second) - A measurement of how fast data is moved from one place to another. A 56K modem can move about 57,000 bits per second. An OC3 can move 155millon bits per second. Bridge A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol, such as Ethernet or Token-Ring. Browser

A Client program (software) that is used to look at various kinds of Internet resources. Byte A set of Bits that represent a single character. Usually there are 8 Bits in a Byte, sometimes more, depending on how the measurement is being made. Certificate Authority An issuer of Security Certificates used in SSL connections. CGI -- (Common Gateway Interface) A set of rules that describe how a Web Server communicates with another piece of software on the same machine, and how the other piece of software talks to the web server. Any piece of software can be a CGI program if it handles input and output according to the CGI standard. Cgi-bin The most common name of a directory on a web server in which CGI programs are stored. Client A software program that is used to contact and obtain data from a Server software program on another computer, often across a great distance. Each Client program is designed to work with one or more specific kinds of Server programs, and each Server requires a specific kind of Client. A Web Browser is a specific kind of Client. CO-- Short for central office In telephony, a CO is a telecommunications office centralized in a specific locality to handle the telephone service for that locality. Telephone lines are connected to the CO on a local loop. The CO switches calls between local service and long-distance service. ISDN and HSI signals also channel through the CO. Co-location Most often used to refer to having a server that belongs to one person or group physically located on an Internetconnected network that belongs to another person or group. Usually this is done because the server owner wants their machine to be on a high-speed Internet connection and/or they do not want the security risks of having the server on their own network. CPU -- (Abbreviation of central processing unit) Pronounced as separate letters. The CPU is the brains of the computer. Sometimes referred to simply as the processor or central processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system. Cookie The most common meaning of "Cookie" on the Internet refers to a piece of information sent by a Web Server to a Web Browser that the Browser software is expected to save and to send back to the Server whenever the browser makes additional requests from the Server. CSU/DSU--(Short for Channel Service Unit/Data Service Unit) The CSU is a device that connects a terminal to a digital line. Typically, the two devices are packaged as a single unit. The DSU is a device that performs protective and diagnostic functions for a telecommunications line. You can think of it as a very high-powered and expensive modem. Such a device is required for both ends of a T-1 or T-3 connection, and the units at both ends must be set to the same communications standard. DHTML -- (Dynamic HyperText Markup Language) DHTML refers to web pages that use a combination of HTML, JavaScript, and CSS to create features such as letting the user drag items around on the web page, some simple kinds of animation, and many more. DNS -- (Domain Name System) The Domain Name System is the system that translates Internet domain names into IP numbers. A "DNS Server" is a server that performs this kind of translation. Domain Name

The unique name that identifies an Internet site. Domain Names always have 2 or more parts, separated by dots. The part on the left is the most specific, and the part on the right is the most general. A given machine may have more than one Domain Name but a given Domain Name points to only one machine. DoS Attack-- (Short for denial-of-service attack) A type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic. Many DoS attacks, such as the Ping of Death and Teardrop attacks, exploit limitations in the TCP/IP protocols. For all known DoS attacks, there are software fixes that system administrators can install to limit the damage caused by the attacks. But, like viruses, new DoS attacks are constantly being dreamed up by hackers. Download Transferring data (usually a file) from another computer to the computer your are using. The opposite of upload. HSI -- (High Speed Internet) A method for moving data over regular phone lines. A HSI circuit is much faster than a regular phone connection, and the wires coming into the subscriber's premises are the same (copper) wires used for regular phone service. A HSI circuit must be configured to connect two specific locations, similar to a leased line (however a HSI circuit is not a leased line. A common configuration of HSI allows downloads at speeds of up to 1.544 megabits (not megabytes) per second, and uploads at speeds of 128 kilobits per second. This arrangement is called AHSI: Asymmetric High Speed Internet. Another common configuration is symmetrical: 384 Kilobits per second in both directions. In theory ADSL allows download speeds of up to 9 megabits per second and upload speeds of up to 640 kilobits per second. HSI is now a popular alternative to Leased Lines and ISDN, being faster than ISDN and less costly than traditional Leased Lines. email Email -- (Electronic Mail) Short for electronic mail, the transmission of messages over communications networks. The messages can be notes entered from the keyboard or electronic files stored on disk. Most mainframes, minicomputers, and computer networks have an e-mail system. Some electronic-mail systems are confined to a single computer system or network, but others have gateways to other computer systems, enabling users to send electronic mail anywhere in the world. Companies that are fully computerized make extensive use of e-mail because it is fast, flexible, and reliable. Ethernet A very common method of networking computers in a LAN. There is more than one type of Ethernet. By 2001 the standard type was "100-BaseT" which can handle up to about 100,000,000 bits-per-second and can be used with almost any kind of computer. Fire Wall A system designed to prevent unauthorized access to or from a private network. 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. FTP -- (File Transfer Protocol) A very common method of moving files between two Internet sites. FTP is a way to login to another Internet site for the purposes of retrieving and/or sending files. There are many Internet sites that have established publicly accessible repositories of material that can be obtained using FTP, by logging in using the account name "anonymous", thus these sites are called "anonymous ftp servers". FTP was invented and in wide use long before the advent of the World Wide Web and originally was always used from a text-only interface. Frame Relay A packet-switching protocol for connecting devices on a Wide Area Network (WAN). Frame Relay networks in the U.S. support data transfer rates at T-1 (1.544 Mbps) and T-3 (45 Mbps) speeds. In fact, you can think of Frame Relay as a way of utilizing existing T-1 and T-3 lines owned by a service provider. Most telephone companies now

provide Frame Relay service for customers who want connections at 56 Kbps to T-1 speeds. Gateway The technical meaning is a hardware or software set-up that translates between two dissimilar protocols, for example a router is a gateway that translates/bridges between its internal network, and the Internet. GIF -- (Graphic Interchange Format) A common format for image files, especially suitable for images containing large areas of the same color. GIF format files of simple images are often smaller than the same file would be if stored in JPEG format, but GIF format does not store photographic images as well as JPEG. See also: JPEG, PNG Gigabyte 1000 or 1024 Megabytes, depending on who is measuring. GUI (Graphical User Interface, pronounced GOO-ee) A program interface that takes advantage of the computer's graphics capabilities to make the program easier to use. Well-designed graphical user interfaces can free the user from learning complex command languages. On the other hand, many users find that they work more effectively with a command-driven interface, especially if they already know the command language. Hit As used in reference to the World Wide Web, "hit" means a single request from a web browser for a single item from a web server; thus in order for a web browser to display a page that contains 3 graphics, 4 "hits" would occur at the server: 1 for the HTML page, and one for each of the 3 graphics. Home Page (or Homepage) Originally, the web page that your browser is set to use when it starts up. The more common meaning refers to the main web page for a business, organization, person or simply the main page out of a collection of web pages, e.g. "Check out AT&T's new Home Page." Host Any computer on a network that is a repository for services available to other computers on the network. It is quite common to have one host machine provide several services, such as SMTP (email) and HTTP (web). HTML -- (HyperText Markup Language) The coding language used to create Hypertext documents for use on the World Wide Web. HTML looks a lot like oldfashioned typesetting code, where you surround a block of text with codes that indicate how it should appear. The "hyper" in Hypertext comes from the fact that in HTML you can specify that a block of text, or an image, is linked to another file on the Internet. HTML files are meant to be viewed using a "Web Browser". HTML is loosely based on a more comprehensive system for markup called SGML. See also: Browser, Hypertext, WWW HTTP -- (HyperText Transfer Protocol) The protocol for moving hypertext files across the Internet. Requires an HTTP client program on one end, and an HTTP server program on the other end. HTTP is the most important protocol used in the World Wide Web (WWW). Hypertext Generally, any text that contains links to other documents - words or phrases in the document that can be chosen by a reader and which cause another document to be retrieved and displayed. ICMP --(Short for Internet Control Message Protocol) An extension to the Internet Protocol (IP) defined by RFC 792. ICMP supports packets containing error, control, and informational messages. The PING command, for example, uses ICMP to test an Internet connection. IMAP -- (Internet Message Access Protocol) IMAP is gradually replacing POP as the main protocol used by email clients in communicating with email servers. Using IMAP an email client program can not only retrieve email but can also manipulate message stored on the server, without having to actually retrieve the messages. So messages can be deleted, have their status changed,

multiple mailboxes can be managed, etc. RFC Code reference: Internet Message Access Protocol - Version 4rev1 . Intranet A private network inside a company or organization that uses the same kinds of software that you would find on the public Internet, but that is only for internal use. Compare with extranet. IP Address -- (Internet Protocol Number) Sometimes called a dotted quad. A unique number consisting of 4 parts separated by dots, e.g. Every machine that is on the Internet has a unique IP number - if a machine does not have an IP number, it is not really on the Internet. Many machines (especially servers) also have one or more Domain Names that are easier for people to remember. For example IP number is IP Spoofing A technique used to gain unauthorized access to computers, whereby the intruder sends messages to a computer with an IP address indicating that the message is coming from a trusted host. To engage in IP spoofing, a hacker must first use a variety of techniques to find an IP address of a trusted host and then modify the packet headers so that it appears that the packets are coming from that host. IRC -- (Internet Relay Chat) Basically a huge multi-user live chat facility. There are a number of major IRC servers around the world, which are linked to each other. Anyone can create a channel and anything that anyone types in a given channel is seen by all others in the channel. Private channels can (and are) created for multi-person conference calls. See also: Server ISDN -- (Integrated Services Digital Network) Basically a way to move more data over existing regular phone lines. ISDN is available to much of the USA and in most markets it is priced very comparably to standard analog phone circuits. It can provide speeds of roughly 128,000 bits-per-second over regular phone lines. In practice, most people will be limited to 56,000or 64,000 bitsper-second. Unlike HSI, ISDN can be used to connect to many different locations, one at a time, just like a regular telephone call, as long the other location also has ISDN. ISP -- (Internet Service Provider) An institution that provides access to the Internet in some form, usually for money. Java Java is a network-friendly programming language invented by Sun Microsystems. Java is often used to build large, complex systems that involve several different computers interacting across networks, for example transaction processing systems. Java is also becoming popular for creating programs that run in small electronic devices, such as mobile telephones. A very common use of Java is to create programs that can be safely downloaded to your computer through the Internet and immediately run without fear of viruses or other harm to your computer or files. Using small Java programs (called "Applets"), Web pages can include functions such as animations, calculators, and other fancy tricks. JavaScript JavaScript is a programming language that is mostly used in web pages, usually to add features that make the web page more interactive. When JavaScript is included in an HTML file it relies upon the browser to interpret the JavaScript. When JavaScript is combined with Cascading Style Sheets (CSS) and later versions of HTML (4.0 and later) the result is often called DHTML. JPEG -- (Joint Photographic Experts Group) JPEG is most commonly mentioned as a format for image files. JPEG format is preferred to the GIF format for photographic images as opposed to line art or simple logo art. Kilobyte A thousand bytes. Actually, usually 1024 (210) bytes. For example 64K LAN -- (Local Area Network)

A computer network limited to the immediate area, usually the same building or floor of a building. Leased Line Refers to line such as a telephone line or fiber-optic cable that is rented for exclusive 24-hour, 7-days-a-week use from your location to another location. The highest speed data connections require a leased line. Fractional-T1, fullT1, T3, OC3 etc. Linux A widely used Open Source Unix-like operating system. Linux was first released by its inventor Linus Torvalds in 1991. There are versions of Linux for almost every available type of computer hardware from desktop machines to IBM mainframes. The inner workings of Linux are open and available for anyone to examine and change as long as they make their changes available to the public. This has resulted in thousands of people working on various aspects of Linux and adaptation of Linux for a huge variety of purposes, from servers to TV-recording boxes. See also: Open Source Software, Unix Local Loop In telephony, a local loop refers to the connection between a telecommunication company's CO to the lines in the service subscriber's home or office. Originally, local loop service carried only telephone service to subscribers. But today, with the use of modems, ISDN and HSI signals are transmitted to subscribers as well through the local loop. Maillist (or Distribution Mailing List) A (usually automated) system that allows people to send e-mail to one address, whereupon their message is copied and sent to all of the other subscribers to the maillist. In this way, people who have many different kinds of e-mail access can participate in discussions together. Megabyte A million bytes. Actually, technically, 1024 kilobytes. Mirror Generally speaking, "to mirror" is to maintain an exact copy of something. Probably the most common use of the term on the Internet refers to "mirror sites" which are web sites, or FTP sites that maintain copies of material originated at another location, usually in order to provide more widespread access to the resource. For example, one site might create a library of software, and 5 other sites might maintain mirrors of that library. Modem -- (Modulator, Demodulator) A device that connects a computer to a phone line. A telephone for a computer. A modem allows a computer to talk to other computers through the phone system. Basically, modems do for computers what a telephone does for humans. NAT-- (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 usually private addresses and a second set of public addresses for external traffic. A NAT box/router/firewall is located where the LAN meets the Internet makes all necessary IP address translations. Netscape A WWW Browser and the name of a company. The Netscape (tm) browser was originally based on the Mosaic program developed at the National Center for Supercomputing Applications (NCSA). See also: Mosaic Network Any time you connect 2 or more computers together so that they can share resources, you have a computer network. Connect 2 or more networks together and you have an Internet. Newsgroup The name for discussion groups on USENET. NIC -- (Network Information Center) Generally, any office that handles information for a network. The most famous of these on the Internet was the InterNIC, which was where most new domain names were registered until that process was decentralized to a

number of private companies. Also means "Network Interface card", which is the card which has a physical port in a computer that you plug a network cable into. NNTP -- (Network News Transport Protocol) The protocol used by client and server software to carry USENET postings back and forth over a TCP/IP network. If you are using any of the more common software such as Netscape, Nuntius, Internet Explorer, etc. to participate in newsgroups then you are benefiting from an NNTP connection. Node Any single host connected to a network. OC -- (Short for Optical Carrier) Used to specify the speed of fiber optic networks conforming to the SONET standard. The following table shows the speeds for common OC levels: OC OC-1 OC-3 OC-12 OC-24 OC-48 = Speed = 51.85 Mbps = 155.52 Mbps = 622.08 Mbps = 1.244 Gbps = 2.488 Gbps

OC-192 = 9.952 Gbps Open Relay Also referred to as an open relay server, an SMTP e-mail server that allows a third party to relay e-mail messages, i.e., sending and/or receiving e-mail that is not for or from a local user. Open relays make it possible for mobile users to connect to corporate networks by going first through a local ISP, which then forwards the message to their home ISP, which then forwards the message to the final destination. However, a downside of open relay technology is the proliferation of its usage by spammers looking to obscure or even hide the source of the large-volume e-mails they send. Operating System The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers OSI-- (Short for Open System Interconnection) A worldwide communications standard that defines a networking framework for implementing protocols in seven layers. OSPF-- (Short for Open Shortest Path First) A routing protocol developed for IP networks based on the shortest path first or link-state algorithm. Routers use link-state algorithms to send routing information to all nodes in an internetwork by calculating the shortest path to each node based on topography of the Internet constructed by each node. Each router sends that portion of the routing table (keeps track of routes to particular network destinations) that describes the state of its own links, and it also sends the complete routing structure (topography) Packet Switching The method used to move data around on the Internet. In packet switching, all the data coming out of a machine is broken up into packets of data, each packet has the address of where it came from and where it is going. This enables data from many different sources to access the same lines, and be sorted and directed along different

routes by special machines/nodes along the way. This way many people can use the same lines at the same time. PAT (Short for port address translation) A type of network address translation. During PAT, each computer on LAN is translated to the same IP address, but with a different port number assignment. PAT is also referred to as overloading, port mapping, port-level multiplexed NAT or single address NAT. Ping To check if a host is up and running on a network. Ping is a command that sends out a packet of data and tests to see if the other host replies back. Often used to check the integrity of a network or internetwork. Derived from the sound that a sonar system makes. A trace-route uses ping to follow the path from host to host to the intended destination. POP -- (Point of Presence, also Post Office Protocol) Two commonly used meanings: Point of Presence and Post Office Protocol. A Point of Presence usually means a city or location where a network can be connected. So if an Internet company says they will soon have a POP in Dallas, it means that they will soon have a local lines in that city. Or a place where leased lines can connect to the ISP's network and ultimately the Internet. A second meaning, Post Office Protocol refers to a way that e-mail client software such as Eudora gets mail from a mail server. When you obtain an account from an Internet Service Provider (ISP) you almost always get a POP account with it, and it is this POP account that you tell your e-mail software to use to get your mail. Another protocol called IMAP is replacing POP for email. Port 2 common meanings: First and most generally, a place where information goes into or out of a computer, or both. E.g. the serial port on a router is where the network connects to the local leased lines. On the Internet port often refers to a number that is part of a URL, appearing after a colon (:) right after the domain name. Every server on an Internet listens on a particular port or ports(s) that correspond to a service it is offering. . Most services have standard port numbers, e.g. Web servers normally listen on port 80. Services can also listen on non-standard ports, in which case the port number must be specified in a URL when accessing the server, so you might see a URL of the form: get2it:// This shows a get2it server running on a non-standard port (the standard get2it port is 7770). Posting A single message entered into a network communications system. PPP -- (Point to Point Protocol) The most common protocol used to connect home computers to the Internet over regular phone lines. Most well known as a protocol that allows a computer to use a regular telephone line and a modem to make TCP/IPconnections and thus be really and truly on the Internet. Protocol On the Internet "protocol" usually refers to a set of rules that define an exact format for communication between systems. For example the HTTP protocol defines the format for communication between web browsers and web servers, the IMAP protocol defines the format for communication between IMAP email servers and clients, and the SSL protocol defines a format for encrypted communications over the Internet. Proxy Server A Proxy Server sits in between a Client and the "real" Server or Network that a Client is trying to use. Clients or workstation are sometimes configured to use a Proxy Server, to get DNS services and its local IP address. The clients makes all of it's requests from the Proxy Server, which then makes requests from the "real" server and passes the result back to the Client. Sometimes the Proxy server will store the results and give a stored result instead of making a new one (to reduce use of a Network). Proxy servers are commonly established on Local Area Networks

PSTN -- (Public Switched Telephone Network) The regular old-fashioned telephone system. RFC -- (Request For Comments) There is a list of common RFCs below that define some of the terms in this document The name of the result and the process for creating a standard on the Internet. New standards are proposed and published on the Internet, as a Request For Comments. The proposal is reviewed by the Internet Engineering Task Force (, a consensus-building body that facilitates discussion, and eventually a new standard is established, but the reference number/name for the standard retains the acronym RFC, e.g. the official standard for e-mail message formats is RFC 822. Router A special-purpose computer (or software package) that handles the connection between 2 or more Packet-Switched networks. Routers spend all their time looking at the source addresses of the packets passing through them and deciding which route or physical port to send them on. SHSI -- (Symmetric High Speed Internet) A version of HSI where the upload speeds and download speeds are the same. See also: AHSI, HSI Search Engine Usually web-based system for searching the information available on the Web. Some search engines work by automatically searching the contents of other systems and creating a database of the results. Other search engines contain only material manually approved for inclusion in a database, and some combine the two approaches. Security Certificate Information (often stored as a text file) that is used by the SSL protocol to establish a secure connection. Often used for e-commerce. Server A computer, or a software package, that provides a specific kind of service to client software running on other computers. The term can refer to a particular piece of software, such as a WWW server, or to the machine on which the software is running, e.g. "Our mail server is down today, that's why e-mail isn't getting out." A single server machine can (and often does) have several different server software packages running on it, thus providing many different servers to clients on the network. Sometimes server software is designed so that additional capabilities can be added to the main program by adding small programs known as servlets. SMDS -- (Switched Multi megabit Data Service) A standard for very high-speed data transfer. SMTP -- (Simple Mail Transfer Protocol) The main protocol used to send electronic mail from server to server on the Internet. SMTP is defined in RFC 821. SNMP -- (Simple Network Management Protocol) A set of standards for communication with devices connected to a TCP/IP network. Examples of these devices include routers, hubs, and switches. SNMP is defined in RFC 1089 SOHO Short for small office/home office, a term that refers to the small or home office environment and the business culture that surrounds it. A SOHO is also called a virtual office. SONET -- (Short for Synchronous Optical Network) Defines interface standards at the physical layer of the OSI seven-layer model. The standard defines a hierarchy of interface rates that allow data streams at different rates to be multiplexed.

Spam (or Spamming) An inappropriate attempt to use a mailing list, or USENET or other networked communications facility as if it was a broadcast medium (which it is not) by sending the same message to a large number of people who did not ask for it. The term probably comes from a famous Monty Python skit, which featured the word Spam repeated over and over. SQL -- (Structured Query Language) A specialized language for sending queries to databases. Most industrial-strength and many smaller database applications can be addressed using SQL. Each specific application will have its own slightly different version of SQL implementing features unique to that application, but all SQL-capable databases support a common subset of SQL. An example of an SQL statement is: SELECT name, email FROM people_table WHERE contry='uk' SSL -- (Secure Socket Layer) A protocol designed by Netscape Communications to enable encrypted, authenticated communications across the Internet. Stateful Inspection Also referred to as dynamic packet filtering. Stateful inspection is a firewall architecture that works at the network layer. Unlike static packet filtering, which examines a packet based on the information in its header, stateful inspection tracks each connection traversing all interfaces of the firewall and makes sure they are valid. Switch In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. Switching also is the act of moving a packet from one port to another. T-1 A leased-line connection capable of carrying data at 1,544,000 bits-per-second. At maximum theoretical capacity, a T-1 line could move a megabyte in less than 10 seconds. That is still not fast enough for full-screen, full-motion video or voice. T-1 lines are commonly used to connect e LANs to the Internet. T-3 A leased-line connection capable of carrying data at 44,736,000 bits-per-second. This is more than enough to do full-screen, full-motion video. At T3 the equivalent to 28 T1 lines TCP/IP -- (Transmission Control Protocol/Internet Protocol) This is the suite of protocols that defines the Internet. Originally designed for the UNIX operating system, TCP/IP software is now included with every major kind of computer operating system. To be truly on the Internet, your computer must have TCP/IP software. Telnet The command and program used to login on port 23 from one Internet site to another. The telnet command/program gets you to the login: prompt of another host. Terminal A device that allows you to send commands to a computer somewhere else. At a minimum, this usually means a keyboard and a display screen and some simple circuitry. Usually you will use terminal software in a personal computer - the software pretends to be (emulates) a physical terminal and allows you to type commands to a computer somewhere else. Terminal Server A special purpose computer that has places to plug in many modems on one side, and a connection to a LAN or

host machine or router on the other side. Thus the terminal surpasses the connections on to the appropriate physical port. TFTP -- (Abbreviation of Trivial File Transfer Protocol) A simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP) and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and routers. TLD -- (Top Level Domain) The last (right-hand) part of a complete Domain Name. For example in the domain name ".net" is the Top Level Domain. There are a large number of TLD's, for example .biz, .com, .edu, .gov, .info, .int, .mil, .net, .org, and a collection of two-letter TLD's corresponding to the standard two-letter country codes, for example, .us, .ca, .jp, etc. See also: Domain Name Trojan Horse A computer program is either hidden inside another program or that masquerades as something it is not in order to trick potential users into running it. For example a program that appears to be a game or image file but in reality performs some other function. A Trojan Horse computer program may spread itself by sending copies of itself from the host computer to other computers, but unlike a virus it will (usually) not infect other programs. See also: Virus, Worm. Tunnel A technology that enables one network to send its data via another network's connections. Tunneling works by encapsulating a network protocol within packets carried by the second network. For example, Microsoft's PPTP technology enables organizations to use the Internet to transmit data across a VPN. It does this by embedding its own network protocol within the TCP/IP packets carried by the Internet. UDP -- (User Datagram Protocol) One of the protocols for data transfer that is comparable to the TCP/IP suite of protocols. UDP is a "connectionless" protocol in that UDP makes no provision for acknowledgement of packets received. Unix A computer operating system (the basic software running on a computer, underneath things like word processors and spreadsheets). Unix is designed to be used by many people at the same time (it is multi-user) and has TCP/IP built-in. It is the most common operating system for servers on the Internet. Upload Transferring data (usually a file) from the computer you are using to another computer. The opposite of download. URL -- (Uniform Resource Locator) The term URL is basically synonymous with URI. URI has replaced URL in technical specifications. See also: URI, URN USENET A world-wide system of discussion groups, with comments passed among hundreds of thousands of machines. Not all USENET machines are on the Internet. USENET is completely decentralized, with over 10,000 discussion areas, called newsgroups. Virus A computer programming code that makes copies of itself without any intervention from the user. Some viruses do more than simply replicate themselves, they might display messages, install other software or files, delete software of files, etc. A virus requires the presence of some other program to replicate itself. Typically viruses spread by

attaching themselves to programs and in some cases files, for example the file formats for Microsoft word processor and spreadsheet programs allow the inclusion of programs called "macros" which can in some cases be a breeding ground for viruses. VPN -- (Virtual Private Network) Usually refers to a network in which some of the parts are connected using the public Internet, but the data sent across the Internet is encrypted, so the entire network is "virtually" private. See also: Internet WAN -- (Wide Area Network) Any Internet or network that covers an area larger than a single building or campus or ISP Web Short for "World Wide Web." Web page A document designed for viewing in a web browser downloaded from a web server. Wi-Fi -- (Short for wireless fidelity) Wi-Fi used as the global brand name across all markets for any 802.11-based (Ethernet) wireless LAN products. Typically any Wi-Fi product using the same radio frequency (for example, 2.4GHz for 802.11b or 11g, 5GHz for 802.11a) are interoperable. worm Worm A worm is a virus that does not infect other programs. It makes copies of itself, and infects additional computers (typically by making use of network connections) but does not attach itself to additional programs; however a worm might alter, install, or destroy files and programs. See also: Trojan Horse, Virus WWW WWW -- (World Wide Web) World Wide Web (or simply Web for short) is a term frequently used (incorrectly) when referring to "The Internet"; WWW has two major meanings: First, loosely used: the whole constellation of resources that can be accessed using Gopher, FTP, HTTP, telnet, USENET, WAIS and some other tools. Second, the universe of hypertext servers (HTTP servers), more commonly called "web servers", which are the servers that serve web pages to web browsers. XML -- (eXtensible Markup Language) A widely used system for defining data formats. XML provides a very rich system to define complex documents and data structures such as invoices, molecular data, news feeds, glossaries, inventory descriptions, real estate properties, etc. As long as a programmer has the XML definition for a collection of data (often called a "schema") then they can create a program to reliably process any data formatted according to those rules.

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