How The Internet Works

Linking Networks to the Internet (5/7)

Satellites can also link networks, as can fiber-optic cables, special IDSN (Integrated Services Digital Network) telephone lines, or high-speed DSL connections.

File Types on the Internet (3/6)

Several different file types, such as PostScript (which ends in a .ps extension) and Adobe Acrobat (.pdf) files, contain complex information about documents. This includes placement of pictures, size and type of fonts, and the complex shapes and formatting information that is needed in order to view the page. PostScript and Acrobat files. These formatted pages on your screen over the Internet and print them if you want.

Common Domains in the U.S.:

1. .com (commercial) 2. .edu (education) 3. .gov (government) 4. .mil (military) 5. .net (network) 6. .org (organization) 7. .web (web) 8. .au (Australia) 9. .ca (Canada) 10. .uk (United Kingdom) 11. .fr (France)

Internet2

A U.S.-based and international nonprofit networking consortium led by researchers, academia and industry/government leaders. Launched in 1996, Internet2 works to advance the development of networking education and global partnering to facilitate innovative Internet technologies. Internet2 manages the Internet2 Network, a next-generation optical and Internet Protocol network. Internet2 Network is responsible for delivering production network services to fulfill the high-performance requirements of education and research services. It also provides its users with a protected research and network testing environment.

Binary Files

A binary file is a type of computer file that is used to store binary data. It may contain any type of formatted or unformatted data encoded within binary format. It is used directly by the computer and generally can't be read by a human. Binary files may also be called binaries.

SLIP (Serial Line Internet Protocol)

A communications protocol that enables a workstation to connect to a server using a serial connection. SLIP can support only asynchronous communications and IP traffic and requires some configuration on the client workstation. SLIP has been made obsolete by PPP.

(Data) Packet

A container or box that carries data over a TCP/IP network and internetworks. A packet is the most fundamental logical arbitration of data that is passed over a network.

Domain

A domain, in the context of networking, refers to any group of users, workstations, devices, printers, computers and database servers that share different types of data via network resources. There are also many types of subdomains. A domain has a domain controller that governs all basic domain functions and manages network security. Thus, a domain is used to manage all user functions, including username/password and shared system resource authentication and access. A domain is also used to assign specific resource privileges, such as user accounts.

How Web Connections Work (1/5)

A fast connection is essential for Web cruising. You might use a 28.8Kbps (kilobits per second), 56Kbps, or faster modem that converts digital information from the computer into the analog signals transmitted by ordinary phone lines (sometimes called POTS, or plain old telephone service). ISDN lines that transfer digital data at speeds up to 128Kbps are available in some residential areas. Faster still are ADSL (asynchronous digital subscriber line) lines that transmit and receive digital data at 144Kbps or faster. And cable modems also can receive data at 1.5Mbps.

RFCs (Requests for Comment)

A formal document drafted by the Internet Engineering Task Force (IETF) that describes the specifications for a particular technology. When an RFC is ratified, it becomes a formal standards document; first used during the creation of the ARPANET protocols that came to establish what became today's Internet. They continue to be issued on an ongoing basis as the technology underlying the Internet evolves.

Network

A group of two or more devices or nodes that can communicate. The devices or nodes in question can be connected by physical or wireless connections. The key is that there are at least two separate components, and they are connected. The scale of a network can range from a single pair of devices or nodes sending data back and forth, to massive data centers and even the global Internet, the largest network in existence. What all of these networks have in common, from the smallest ones to the largest, is that they allow computers and/or users to share information and resources.

Local (Area) Networks

A local area network (LAN) is a computer network within a small geographical area such as a home, school, computer laboratory, office building or group of buildings. A LAN is composed of inter-connected workstations and personal computers which are each capable of accessing and sharing data and devices, such as printers, scanners and data storage devices, anywhere on the LAN. LANs are characterized by higher communication and data transfer rates and the lack of any need for leased communication lines.

Regional Network

A midlevel network in a geographic area.

Transmission Control Protocol (TCP)

A network communication protocol designed to send data packets over the Internet; a transport layer protocol in the OSI layer and is used to create a connection between remote computers by transporting and ensuring the delivery of messages over supporting networks and the Internet. Before transmitting data, TCP creates a connection between the source and destination node and keeps it live until the communication is active. TCP breaks large data into smaller packets and also ensures that the data integrity is intact once it is reassembled at the destination node.

Modem

A network device that both modulates and demodulates analog carrier signals (called sine waves) for encoding and decoding digital information for processing. Modems accomplish both of these tasks simultaneously and, for this reason, the term modem is a combination of "modulate" and "demodulate."

Packet-Switched Network

A packet switched network (PSN) is a type of computer communications network that groups and sends data in the form of small packets. It enables the sending of data or network packets between a source and destination node over a network channel that is shared between multiple users and/or applications. A packet switched is also known as a connectionless network, as it does not create a permanent connection between a source and destination node.

How Routers Work (1/6)

A router has input ports for receiving IP packets and output ports for sending those packets toward their destination. When a packet comes to an input port, the router examines the packet header and checks the destination in it against a routing table, a database that tells the router how to send packets to various destinations.

How Routers Work (4/6)

A simple kind of routing table is called a static routing table. In static routing, the routing table has specific ways of routing data to other networks. Only those pathways can be used. New routes can be added to the routing table. Static routing can't just adjust routes as network traffic changes so it isn't an optimal alternative for many routers.

Socket or TCP/IP Stack

A socket is a software object that acts as an end point establishing a bidirectional network communication link between a server-side and a client-side program. In UNIX, a socket can also be referred to as an endpoint for interprocess communication(IPC) within the operating system(OS). In Java, socket classes represent the communication between client and server programs. Socket classes handle client-side communication, and server socket classes handle server-side communication.

Username

A username is a a word, phrase, number or combination of characters that uniquely identifies a user on software, a website, a computer or any computing device or related service that requires user authentication. A username is a distinctive alphabetical and numerical set of characters used to identify and gain access to a computing system. A username is also known as a login ID.

Circuit Switched Network

After a connection is made, that part of the network is dedicated only to that single connection.

ASCII Files

American Standard for Information Interchange (ASCII) is a method of encoding characters that is based on the order of alphabetic characters in the English language. ASCII integer representations have printable and nonprintable subsets. Printable characters are normal characters, and nonprintable characters are characters used to represent keyboard keys, e.g., backspace, delete, and return.

Repeaters

Amplify the data at intervals so the signal doesn't weaken.

IP Address Example

An Internet Protocol address (IP address) is a logical numeric address that is assigned to every single computer, printer, switch, router or any other device that is part of a TCP/IP-based network. The IP address is the core component on which the networking architecture is built; no network exists without it. An IP address is a logical address that is used to uniquely identify every node in the network. Because IP addresses are logical, they can change. They are similar to addresses in a town or city because the IP address gives the network node an address so that it can communicate with other nodes or networks, just like mail is sent to friends and relatives. The numerals in an IP address are divided into 2 parts: 1. The network part specifies which networks this address belongs to and. 2. The host part further pinpoints the exact location.

How Internet Addresses Work (2/7)

An Internet address is made up of two major parts separated by an @ (at) sign. The address can tell you a good deal of information about the person who "owns" the address. The first part of the address (to the left of the @ sign) is often that person's login name or in some way identifies him or her. The second part of the address (to the right of the @ sign) contains the hostname (which can refer to a specific server on a network) followed by the Internet address, which together identify the specific computer where the person has an Internet email account.

Internet Service Provider (ISP)

An Internet service provider (ISP) is a company that provides customers with Internet access. It is often referred to as just "the provider." Data may be transmitted using several technologies, including dial-up, DSL, cable modem, wireless or dedicated high-speed interconnects. Typically, ISPs also provide their customers with the ability to communicate with one another by providing Internet email accounts, usually with numerous email addresses at the customer's discretion. Other services, such as telephone and television services, or personal websites or home pages may be provided as well. The services and service combinations may be unique to each ISP. Today, ISPs are usually cable companies or mobile phone companies that offer Internet subscriptions in addition to TV or mobile communications services. An Internet service provider is also known as an Internet access provider (IAP). Advertisement

Anatomy of a Mail Message (1/6)

An email message is made up of binary data, usually in the ASCII text format. ASCII is a standard that enables any computer, regardless of its operating system or hardware, to read the text. ASCII code describes the characters you see on the computer screen.

Internet Domain Name

An identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes

Internet Society

An international nonprofit organization that handles Internet standards, education and policy development. Founded in 1992, ISOC's mission is to ensure open Internet development by enhancing and supporting Internet use for organizations and individuals worldwide.

World Wide Web Consortium (W3C)

An international organization committed to improving the web. It is made up of several hundred member organizations from a variety of related IT industries. W3C sets standards for the World Wide Web (WWW) to facilitate interoperability and cooperation among all web stakeholders. It was established in 1994 by the creator of the WWW, Tim Berners-Lee.

Wide Area Network (WAN)

Another kind of midlevel network. Consists of an organization with many networked sites linked together.

Web 2.0

As engineers added things like Javascript applets and modules to the web, Web 2.0 emerged. Web 2.0 is the read/write web or the functional web, where web fields and forms have allowed users to participate in transactions, upload resources or post their own suggestions in active conversation. By most people's assertions, the Internet that we now use. The problem of "stateless" web-delivered functionality as is Web 2.0, is largely solved by digital "cookies," trackers that save individual user data in the browser to enable things like saved passwords. The trade-off is that user activity is inherently tracked: when a user erases the cookies, that session data is gone, and the user will have to start over as a new guest in any future sessions.

How TCP/IP Works (4/6)

As the packets are sent across the Internet, routers along the way examine the IP envelopes and look at their addresses. These routers determine the most efficient path for sending each packet to the next router closest to its final destination. After travelling through a series of routers, the packets arrive. Because the traffic load on the Internet changes constantly, the packets might be sent along different routes and the packets might arrive out of order.

How TCP/IP Works (5/6)

As the packets arrive at their destination, TCP calculates a checksum for each packet. It then compares this checksum with the checksum that has been sent in the packet. If the checksums don't match, TCP knows that the data in the packet has been corrupted during transmission. It then discards the packet and asks that the original packet be retransmitted.

Anatomy of a Mail Message (6/6)

At the bottom of the message is a "signature" area that can contain personalized information about you. Some mail programs will automatically apend this signature to the bottom of every message you send. Signature areas are jot required and are used at the discretion of the person who creates the email message. Signatures should not exceed five lines.

How Routers Work (2/6)

Based on information in the routing table, the packet is sent to a particular output port, which sends the packet to a router that is one step closer to the packet's destination.

What a Network is used for

Communications such as email, instant messaging, chat rooms, etc Shared hardware such as printers and input devices Shared data and information through the use of shared storage devices Shared software, which is achieved by running applications on remote computers

How Web Connections Work (4/5)

Computers with dedicated links to the Internet backbone must always be on and the connection must always be open. These computers are assigned a permanent IP (Internet Protocol) address, which is a multidigit number. This address enables other machines to find it. When you connect to the Internet via an ISP, your connection to the Internet backbone is opened, and your computer is assigned a temporary ISP address, although some ISPs give you a permanent IP address, which is always yours whenever you connect to the Internet.

Network Access Point (NAP)

Data packets are sent across the country or the world on a backbone.

Connecting Your Computer to the Internet (3/10)

Direct Connection: LANs or large computers such as mainframes can be directly connected to the Internet. When a LAN is connected to the Internet, all the computers on the network can have full access to the Net. This kind of access is common inside corporations.

Connecting Your Computer to the Internet (1/10)

Dumb Terminal: A terminal that is connected to a main frame, minicomputer, or other kind of large computer. This type of connection can often be found in libraries or universities although those institutions are moving toward offering fuller Internet access than dumb terminals provide.

How Routers Work (5/6)

Dynamic routing is more useful than static routing. It allows a packet to have multiple routes to reach its final destination. Dynamic routing also allows routers to change the way they route information based on the amount of network traffic on some paths and routers. In dynamic routing, the routing table is called a dynamic routing table and changes as network conditions change. The tables are built dynamically by routing protocols, constantly changing according to network traffic and conditions.

How Online Services Work (2/7)

Each online service has a great deal of resources, content, and special areas that are not available to anyone except people who subscribe to that particular service. These areas use the online service's own proprietary software and interface; they do not work like the Internet. You dial directly into the online service to get at these resources.

How TCP/IP Works (3/6)

Each packet is put into separate IP "envelopes" which contain addressing information that tells the Internet where to send the data. All the envelopes for a given piece of data have the same addressing information so they can all be sent to the same location to be reassembled. IP "envelopes" contain headers that include information such as the sender address, the destination address, the amount of time the packet should be kept before discarding it, and so on.

Email/e-mail

Electronic mail (email) is a digital mechanism for exchanging messages through Internet or intranet communication platforms.

Services on the Internet

Email Web-enabled audio/video conferencing services Online movies and gaming Data transfer/file-sharing, often through File Transfer Protocol (FTP) Instant messaging Internet forums Social networking Online shopping Financial services

How TCP/IP Works (2/6)

For a number of reasons, including software limitations, data sent across the Internet must be broken up into packets fewer than about 1,500 characters each. Each packet is given a header that contains a variety of information, such as the order in which the packets should be assembled with other related packets. As TCP creates each packet, it also calculates and adds to the header checksum, which is a number that TCP uses on the receiving end to determine whether any errors have been introduced into the packet during transmission. The checksum is based on the precise amount of data in the packet.

Midlevel Networks

Hook LANs together using high-speed telephone lines, ethernet, and microwave links.

Connecting Your Computer to the Internet (6/10)

ISDN Line: Special digital telephone lines, called ISDN lines, can be used to dial into the Internet at high speeds, usually from 64Kbps to 128Kbps. Special ISDN modems must be used with ISDN lines. ISDN lines cost more than normal phone lines, so your telephone rates are usually higher. A newer technology called Asymmetric Digital Subscriber Line (ASDL), allows for very high-speed connections over existing telephone wires.

How the Internet Runs (7/7)

ISPs sell people monthly connections to the Internet. They run their own segments of the Internet and may also supply long-distance connections called backbones. Telephone companies are another source of long-distance connections for the Internet.

Domain Name

Identifies the specific computer where the person has an Internet email account.

How Routers Work (3/6)

If packets come to the input port more quickly than the router can process them, they are sent to a holding area called an input queue. The router then processes packets from the queue in the order they were received. If the number of packets received exceeds the length of the queue, packets might be lost. When this happens, the TCP protocol on the sending and receiving computers will have the packets re-sent.

How Domain Name Systems (DNS Servers Work (3/5)

If the information you have requested isn't on a local network, the local name server may not have the address you're looking for. In that instance, the local name server must get the information from a name server on the Internet. The local namer server contacts the root domain server. The root domain server tells the local server which primary name server and secondary namer server have the information about the requested URL.

Bridges

Link local area networks (LANs) with one another. They enable data destined for another LAN to be sent there, while keeping local data inside its own network.

How Web Connections Work (2/5)

If you're using the telephone system to get onto the Internet, your telecommunications connection follows either the normal phone system (POTS) or an ISDN or ADSL line until it reaches the telephone company's central office. The central office routes calls either through its own network of copper, fiber-optic, or satellite links, or to a long distance carrier's point of presence, or POP. The POP is the point at which a local call is handed off to a long distance company. The call is then routed to the central office nearest your Internet Service Provider, also called ISP.

Anatomy of a Mail Message (3/6)

In the To Line, type in the email address of the person to whom you're sending a message. The address must be typed in following very strict rules. If you get a single letter or the syntax wrong, your message won't be able to get to the intended recipient.

Web 1.0

Is the original incarnation of the Internet as a place where most data was read-only. Web 1.0 is often described by experts as an Internet where the most common kinds of activity are passive - reading, doing research, or learning about products and services before making a purchase over traditional media, for example, by telephone.

Web 3.0

Is the posited future Internet called the "semantic web," where Internet data will have evolved relationships, and mapping will help automate a lot of what we now do on the Internet manually. The semantic web, proponents suggest, will be a web that is in many ways automated by linking individual virtual objects and websites together in a seamless manner. With that in mind, Web 3.0 may help us to do away with the current model of using cookies for session data retrieval.

Routers

Job is to ensure the packets always arrive at the proper destination. If data is being transferred among computers that are on the same LAN, routers often aren't needed because the network itself can handle its internal traffic. Routers examine packet to determine their destination. They take into account the volume of activity on the Internet, and they send the packets to another router- one that is closer to the packet's final destination.

How the Internet Runs (1/7)

Many private organizations, universities, and government agencies pay for and run parts of it.

How Online Services Work (5/7)

Most services also let you use your client software to access the Internet resources such as Telnet, Gopher, FTP, and IRC that the services do not have proprietary software for. In order to do this, you dial into the online service and establish a TCP/IP connection. You can get directly onto the Internet using your own client software.

Connecting Your Computer to the Internet (8/10)

Network Computer: Some people believe that a low-cost Network Computer will eventually be widely used to access the Internet. This would be a computer, modem, and monitor that would not include a hard disk or CD-ROM drive or very much processing power. Programs would be stored on the Internet instead of on the NC.

Linking Networks to the Internet (4/7)

Networks are connected in different ways. Dedicated telephone lines can transmit data at 56bps. An increasing number of T1 leased telephone lines exist that carry data between networks. A T1 link can carry data at 1.544Mbps. If you dial into an ISP from home, you might connect at a lower speed than at your office, where you might have higher-speed connections such as a T1 or 565Kbps.

Anatomy of a Mail Message (5/6)

On the Subject line, type in the subject of your message or a very brief summary.

Connecting Your Computer to the Internet (10/10)

Online Services: All the major online services allow you to tap the full power of the Internet. No special setup is required. When you dial into the online service, you'll be able to use the Internet's resources, including browsing the World Wide Web.

How Online Services Work (6/7)

Online services also let you browse the World Wide Web. One way to browse the Web is to use the online service's own proprietary Web browser. Typically, you can launch a browser by clicking on an icon or going into a special area of the online service.

How Online Services Work (1/7)

Online services such as CompuServe or America Online provide a very convenient way to use Internet resources. These services have their own software that make it easy to access Internet resources such as Telnet, Gopher, and FTP. Some also allow you to use your own Telnet, FTP, Gopher, or other software instead of theirs. using these resources, you may browse the World Wide Web, either with their own proprietary Web browser or by using any other Web browser. Finally, some services let you use special software required to access Internet resources such as IRC (Internet Relay Chat).

How Online Services Work (4/7)

Online services use their own proprietary software and interface to give you access to many common Internet resources, such as Usenet newsgroups, Telnet, Gopher, and FTP. You issue a command using the online service's own software. The online service then sends the command out over the Internet via a gateway to retrieve the information. The information is sent back via a gateway, through the online service's own software, and then to your computer.

Connecting Your Computer to the Internet (5/10)

PPP (Point-to-Point Protocol): Like SLIP, this is a full Internet connection over telephone lines via modem. It is more reliable than SLIP because it double-checkers to ensure that Internet packets arrive intact. It resends any damaged packets.

PPP (Point-to-Point Protocol)

Point-to-point protocol (PPP) is a computer network protocol used to transfer a datagram between two directly connected (point-to-point) computers. This protocol is used for a very basic level of connectivity providing data linkage between the computers. Point-to-point protocol is widely used for the heavier and faster connections necessary for broadband communications. Point-to-point protocol is also known as RFC 1661.

How the Internet Runs (4/7)

Private companies called Internet Registrars are responsible for registering Internet domains, such as www.zdnet.com, to people and businesses. Internet Registrars are overseen by boards made up of people from private and public institutions.

Hardware

Refers to the physical elements that make up a computer or electronic system and everything else involved that is physically tangible. This includes the monitor, hard drive, memory and the CPU. Hardware works hand-in-hand with firmware and software to make a computer function.

Linking Networks to the Internet (7/7)

Regional networks are connected to one another via high-speed back bones- connections that can send data at extremely high speeds. When data is sent from one regional network to another, it is first sent to a Network Access Point (NAP). The NAP then routes the data to high-speed backbones, such as vBNS, which can transmit data at 155Mbps. The data is then sent along the backbone to another regional network. Finally, it is passed to a specific network and computer within that regional network.

How the Internet Runs (3/7)

Regional networks provide and maintain Internet access within a geographic area. Regional nets may consist of smaller networks and organizations within area that have banded together to provide better service.

Linking Networks to the Internet (3/7)

Routers, which connect networks, perform most of the work of directing traffic on the Internet. Routers examine the packets of data that travel across the Internet to see where the data is headed. Based on the data's destination, the packet is routed in the most efficient way, generally to another router, which in turn sends the packet to the next router, and so on.

Connecting Your Computer to the Internet (4/10)

SLIP (Serial Line Internet Protocol): A full Internet connection over telephone lines that sends Internet packets via 9,600bps modems or better.

How Online Services Work (7/7)

Some online services let you use any Web browser you want to browse the World Wide Web. In that instance, you can click on an icon on the online service, go into a special area of the online service, or simply launch your own computer, and then begin browsing the Web.

Connecting Your Computer to the Internet (2/10)

Terminal Emulation: A personal computer can connect via modem to a large computer and run a terminal emulation program. The most common terminal emulation is the VT-100. The computer works like a dumb terminal, except it is connected via a phone line instead of a direct connection. Often, you won't be able to use the graphical part of the Internet, such as the World Wide Web, with this kind of access, although you'll be able to browse the text-only portion of the Web. This kind of Internet account is sometimes called a shell account. Terminal emulation has become increasingly rare.

How Internet Addresses Work (4/7)

The Domain Name System (DNS) divides the Internet into understandable groups, or domains. Note the portion of the domain section at the far right of the address. It identifies the largest domain names and kind of organization where the person's address resides. The domain names and host names identify the host computer where the Internet should deliver the email. The receiving host computer looks at the username and delivers the mail to the proper email box.

How Web Connections Work (3/5)

The ISP receives your incoming call and processes your request, passing the connection to its leased line link to a computer on the Internet backbone, usually a T1 connection or faster. Typically the ISP has a rack of modems that accepts multiple incoming calls simultaneously. Your connection is complete when it reaches the host computer.

How the Internet Runs (5/7)

The InterNIC is responsible for maintaining the domains registered through registries. It tracks the connections between Internet addresses, such as 125.34.24.21, and domain names, such as www.zdnet.com.

Internet Activities Board (IAB)

The Internet Architecture Board (IAB) is a board of researchers and professionals that manages the engineering and technical development related to the Internet. IAB offers assistance and insight on a wide range of Internet-related concerns. Professional entities, standards agencies and other organizations frequently use IAB as a reference for network expertise. IAB manages several task forces, including the Internet Research Task Force (IRTF) and the Internet Engineering Task Force (IETF). IAB was originally established as the Internet Configuration Control Board (ICCB) in 1979. Adopting several names afterwards, it finally became the IAB in 1992. Initially, the U.S. government and Federal Research Internet Configuration Committee (FRICC) supported IAB.

How Internet Addresses Work (1/7)

The Internet Protocol (IP) delivers mail based on the specific email address. This address is expressed as four numbers, separated by periods (called dots), such as 163.52.128.72. However, because it would be difficult to remember such complex addresses, you can instead use Internet addresses made up of words and letters. Computers called domain name servers translate the alphabetical address into a numerical address, so email can be sent to the proper location.

How the Internet Runs (6/7)

The Internet Society is a private nonprofit organization that makes technological and architectural recommendations that pertain to the Internet, such as how TCP/IP and other Internet protocols should work. This body guides the direction of the Internet and its growth.

Connecting Your Computer to the Internet (7/10)

The Internet can be accessed over some cable TV systems using the coaxial cable that carries television signals. A special cable modem must be used. Cable modems might be able to send and receive data at speeds from 20 to 100 times as fast as conventional modems.

Linking Networks to the Internet (1/7)

The Internet compromises networks that are attached to one another via pathways that facilitate the exchange of information, data, and files. Being connected to the Internet means having access to these pathways. Your computer can send packets of data over these pathways to any other computer connected to the Internet.

How TCP/IP Works (1/6)

The Internet is a packet-switched network, which means that when you send information across the Internet from your computer to another computer, the data is broken into small packets. A series of switches called routers send each packet across the Net individually. After all the packets arrive at the receiving computer, they are recombined into their original, unified form. Two protocols do the work of breaking the data into packets, routing the packets across the Internet, and then recombining them on the other end: The Internet Protocol (IP), which routes the data, and the Transmission Control Protocol (TCP), which breaks the data into packets and recombines them on the computer that receives the information.

Desktop

The command and control station from which you direct your navigation of the Web.

How Internet Addresses Work (7/7)

The domain and hostnames tell the Internet to which computer the email should be delivered. The receiving host computer looks at the username and delivers the mail to the proper email box.

How the Internet Runs (2/7)

The high-speed Backbone Network Service (vBNS) provides infrastructure for the research and education community by linking together super computer centers.

How Web Connections Work (5/5)

The host runs special Web server software that reads requests sent from the client computer. The host also retrieves and sends the appropriate information to the client. These host computers might have dedicated T1 or T3 links to the Internet backbone, or might be connected to the backbone through a network of hosts.

Internet (1/2)

The internet is a globally connected network system facilitating worldwide communication and access to data resources through a vast collection of private, public, business, academic and government networks. It is governed by agencies like the Internet Assigned Numbers Authority (or IANA) that establish universal protocols. The terms internet and World Wide Web are often used interchangeably, but they are not exactly the same thing; the internet refers to the global communication system, including hardware and infrastructure, while the web is one of the services communicated over the internet.

History of the Internet

The internet originated with the U.S. government, which began building a computer network in the 1960s known as ARPANET. In 1985, the U.S. National Science Foundation (NSF) commissioned the development of a university network backbone called NSFNET. The system was replaced by new networks operated by commercial internet service providers in 1995. The internet was brought to the public on a larger scale at around this time.

How Domain Name Systems (DNS Servers Work (4/5)

The local name server now contacts the primary name server. If the information cannot be found in the primary name server, the local name server contacts the secondary name server. One of the those name servers will have the proper information. It will then pass the information back to the local name server.

How Domain Name Systems (DNS Servers Work (5/5)

The local name server sends the information back to you. Your Web browser now uses the IP address to contact the proper site.

Linking Networks to the Internet (6/7)

The network in a particular geographic area are connected into a large regional network. Routers pass information within that area from network to network.

Internet Protocol (IP)

The principal set (or communications protocol) of digital message formats and rules for exchanging messages between computers across a single network or a series of interconnected networks, using the Internet Protocol Suite (often referred to as TCP/IP). Messages are exchanged as datagrams, also known as data packets or just packets. IP is the primary protocol in the Internet Layer of the Internet Protocol Suite, which is a set of communications protocols consisting of four abstraction layers: link layer (lowest), Internet layer, transport layer and application layer (highest).

File Types on the Internet (1/6)

There are many different types of files on the Internet. Each file has information contained in its header. The header is simply the first line of a file or a specific number of bytes at the beginning of a file. Software that can read or view the file looks into the header of a file to distinguish what kind of file it is, and then processes the file accordingly.

File Types on the Internet (5/6)

There are many executable programs you'll find on the Internet that you can download to your computer and use just like any other kind of software. Because these software files can be large and take a long time to download, they are often compressed to make them download faster. After a file is on your computer, you uncompress it with special decompression software and run it like any other program. Frequently, PC software has been compressed with PKZIP and has a .zip extension, whereas Macintosh software can be compressed with a variety of compression software. In genera, PC files can only be used with PCs, whereas Macintosh files can only be used with Macintoshes.

How Routers Work (6/6)

There are two broad types of routing protocols: interior and exterior. Interior routing protocols are typically used only on routers in a company's intranet, or internal network. These inferior routing protocols route traffic bound only for inside the intranet. A common interior routing protocol is the Routing Information Protocol (RIP). Exterior protocols are typically used for routers located on the Internet. A common exterior routing protocol is the Exterior Gateway Protocol (EGP).

Hubs

They link groups of computers to one another and let computers communicate with each other.

How Web Connections Work Note

To get onto the Web, you'll need an IP address. If you get onto the Web at work via a LAN, the odds are you have a single IP address that is used every time you go onto the Internet. However, when you dial in from home, your IP address need not be the same every time you dial in. By doing this, ISPs keep down the number of IP address they need to maintain.

How Internet Addresses Work (6/7)

To the left of the Internet address is the hostname, which tells routers to which specific computer within the domain the email should be delivered.

How Internet Addresses Work (5/7)

To the left of the largest domain is specific information about the organization, which should be sent. It can be a single Internet address, such as zd (for Ziff-Davis), or it can be a group of domains and subdomains, such as mfsc.nasa.

Gateways

Translate data from one kind of network to another.

Connecting Your Computer to the Internet (9/10)

WebTV: You can also access the Internet directly on your television set by using a set-top box that dials into the Internet and then displays Web pages on your television set. The best known of these is the WebTV set-top box and network. And you can also use satellite dishes that are similar to television satellite dishes to access the Internet.

How Domain Name Systems (DNS Servers Work (1/5)

When a particular uniform resource locator (URL) needs to be contacted, the address with the URL must be matched to the true IP address. Your web browser first goes to a local name server maintained by your ISP, online service, or company to get this information. If the IP address is a local one, on the same network as the one you are on, the name server will be able to resolve the URL with the IP address It will send the true IP address to your computer.

How TCP/IP Works (6/6)

When all the noncorrupt packets are received by the computer to which the information is being sent, TCP assembles them into their original, unified form.

How Internet Addresses Work (3/7)

When you send email, it goes to a name server. In order to deliver the email, the Internet needs to know the numeric IP address, such as 163.52.128.72. Name servers look up the alphabetical address and substitute the numeric IP address for it so the email can be delivered properly.

How Online Services Work (3/7)

When you use the resources of an online service, you don't go outside the service to the Internet, instead, you stay behind a firewall. A firewall is a security system of accepting or blocking packets as they are transmitted across a network. Individual online services establish firewalls that only let subscribers into the service.

Anatomy of a Mail Message (2/6)

You can also attach pictures, executable programs, sounds, videos, and other binary files to your email messages. To do this, you'll have to encode the file in a way that will enable it to be sent across the Internet. The receiver will also have to be able to decode the file after it is received. A variety of encoding schemes can be used. Some email software will automatically do the encoding for you and will also do the decoding on the receiving end.

Linking Networks to the Internet (2/7)

You get onto the Internet through a LAN at your home or place of business in one of two ways. You can dial into a large computer connected to the Internet via an online service of a dial-in Internet service provider (ISP), or you can use cable modem. Ethernet networks and token-ring networks are two kinds of networks that can be connected to the Internet. Token-ring networks pass data in "tokens" from computer to computer in a ring or star configuration. In Ethernet networks, the data goes from a server to a computer on the network.

File Types on the Internet (2/6)

You'll find graphics files in many formats, including GIF, JPEG, PNG, PCX, and TIF are two of the most common graphics formats. They allow the exchange of image files between different kinds of computers and can be downloaded to your computer quickly. A GIF reader or JPEG reader can read binary GIF and JPEG files and display them on your computer. Graphics programs will typically read both types of files. A GIF file contains the binary data that will display an image when viewed from the proper reader. Your computer's video card takes information from the reader and displays it on your computer's monitor. Both GIF and JPEG are the commonly used graphics formats in Web Pages. Your Web browser has the capability to read and display these files on Web pages without needing any added software.

File Types on the Internet (6/6)

You'll find many ASCII text files on the Internet that you can read with a text editor or word processor. These can be articles, FAQs (frequently asked questions and their answers), or any other kind of informational files.

File Types on the Internet (4/6)

You'll find many different kinds of binary multimedia files on the Internet that let you listen to or play sounds, music, and videos. Windows sound files are common types of files that you can download to your computer and play with a sound player, as are music files in the MP3 format (these end in an .mp3 extension). Other sound files, such as those created by RealAudio software, allow you to listen to the sounds while the file is downloading. This process is called streaming audio. Windows .avi files are common animation files. Macintosh QuickTime and MPEG files (which end in an .mpg extension) are common video formats. Other animation files allow you to watch the video while the video is downloading. This process is called streaming video. You'll need special software to use all of these types of files.

How Domain Name Systems (DNS Servers Work (2/5)

Your Web Browser now has the true IP address of the place you're trying to locate. It uses that IP address and contacts the site. The site sends you the information you've requested.

Anatomy of a Mail Message (4/6)

Your email address will appear on the From line. Using this address, the recipient of your message will be able to respond to you.