The Internet is a large collection of computers all over the world; connected to each other in various ways. The Internet lets you communicate with others either via email, reading online newspapers, discussion groups, playing games, e-commerce and even obtain free software.
The World Wide Web (WWW) is a subset of the computers on the Internet that are connected to each other in a way that makes those computers and their content accessible to all computers in that subset.
The Internet began as a way for the military to maintain control while under attack.
NIC: Network Interface card. A device used to connect a computer to a Network or LAN.
LAN: Local Area Network. A small group of computers sharing resources consisting of Servers, Clients, Printers and other devices located in close proximity to one another (usually in one building or one floor of a building)
Server: is a general term for any computer that accepts requests from other computers that are connected to it and shares some or all of its resources, such as files, printers, programs, with other computers.
Clients: request information from servers or other clients, such as files, printers, programs & other shared resources.
NOS: Network Operating System. The NOS runs on the server computer.
Client/Server Network: is when a client will request a service or resources and the server provides that service or resource.
Peer-to-Peer: the client acts like a server and a client. When a client provides a service, the device is a "server", and when the client makes a request, it is a "client"
PC: Personal Computers. Can be used as servers of small networks.
Mini-computers and Mainframe Computers: are larger, more expensive computers that businesses and other organizations use to process large volumes of work at high speeds.
Twisted-Pair cable: has two or more insulated copper wires that are twisted around each other and enclosed in another layer of plastic insulation. The wires are twisted to reduce interference from other nearby cable types.
Coaxial cable: is an insulated copper wire encased in a metal shield that is enclosed with plastic insulation. Then signal within the cable is shielded, therefore has a higher resistance to electrical interference . Coaxial cable is faster than Twisted-pair (about 20x faster) but is considerably more expensive than Twisted-pair.
Fiber Optic cable: does not use an electrical signal, rather it uses pulsing beams of light through very thin stands of glass. Very fast and has a high resistance to EMI. It is lighter and more durable than coaxial, but extremely hard to work with and very expensive.
Wireless Networks: Uses infrared, microwave or satellite.
WAN: Wide Area Network. Several LANs connected together to form an internet.
internet: interconnected network. WAN
Internet: is a specific worldwide collection of interconnected networks whose owners have voluntarily agreed to share resources and network connections with each other. Or a huge interconnected network.
In the early 1960's the US DOD became very concerned about the possible effects of nuclear attack on its computing facilities. The DOD started out by connecting their mainframes and weapon facilities together. The organization that was tasked to do this was ARPA or DARPA (Advanced Research Projects Agency).
The early methods of networking computers were the telephone companies, through leased lines. The centrally controlled, single connection, all data traveled this single connection. This method is called circuit switching.
However the DARPA folks turned to a different method of sending data, packet switching. Packet switching, implemented in 1969, breaks up a file or message into packets that are labeled electronically with codes for their origin and destination. The packets travel from computer to computer along the network until they reach their destination. The destination computer collects the packets and reassembles the original data from the pieces in each packet. A router is usually the device associated with packet switching. Each time the packet travels through a router, the router will make the best determination to the destination by the use of routing algorithms. Routing algorithms determines the best path for packets to travel to its destination.
In 1967, DARPA researchers had published their plan for packet switching. And in 1969, DARPA connected the first computer switches at UCLA, SRI International, UC at Santa Barbara, and University of Utah at Salt Lake. This experimental WAN was called the ARPANET. Over the next three years, 20 computers had been added to the WAN and they used the Network Control Protocol (NCP). A protocol is a set of rules for data communication, such as formatting, ordering, and error-checking data sent across a network.
Check out a more comprehensive writing about the history of the Internet here.
Four keys to Open Architecture
Independent
networks should not require any internal changes to be connected to the Internet
Packets
that do not arrive at their destinations must be retransmitted from their source
network
The
router computers do not retain information about the packets they handle
No
global control will exist over the network
ARPANET developed a new suite of protocols (TCP/IP) Transmission Control Protocol / Internet Protocol. TCP establishes the connection method used by computers on a network, while IP establishes the rules of routing individual data packets. Many people consider Vincent Cerf to be the father of the Internet, because of an article he and Kahn wrote in 1974 about TCP.
In 1972, Ray Tomlinson wrote a program that could send and receive messages over the network, the beginning of email. In 1976, the Queen of England sent an e-mail message over the ARPANET.
Mailing List - is an e-mail address that takes any message it receives and forwards it to any user who has subscribed to the list.
In 1979, Duke and UNC started Usenet, User's News Network. USNET allows anyone the connects with the network to read and post articles on a variety of subjects. Today, we call this Newsgroups.
By 1981, the ARPANET had over 200 networks and still developing at an accelerated rate. And in 1976, the ARPANET began sending packets via satellite.
The development of the TCP/IP suite also included several tools; for performing the transfer of files (FTP) and remote assess of files (Telnet).
FTP
File Transfer Protocol - transfer files to and from a computer running FTP services. FTP is an interactive system. It must talk with an FTP server. It uses TCP to handle communications and creates a session between the hosts.
Telnet
Telnet - terminal emulation. The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. To start a Telnet session, you must log in to a server by entering a valid username and password. Telnet is a common way to remotely control Web servers.
Are LANs or WANs that use TCP/IP protocol but do not connect to sites outside, like on the Internet.
Internet Engineering Task Force (IETF) is a self-organized group that makes technical contributions to the engineering of the Internet and its technologies. It is the main body that develops new Internet standards.
World Wide Web is based on hypertext and graphical user interfaces (GUIs).
Origins of Hypertext
1945 - Vannevar Bush wrote an article in the Atlantic Monthly about ways scientists could apply skills they had learned during WWII and apply them to peacetime applications. He speculated engineers would build a machine "Memex", which would store all of a person's books, records, letters, and research results on microfilm.
1960's - Ted Nelson described a similar system in which text from one page would link to another page of text. He called this "hypertext". Douglas Englebert created the first experimental hypertext system on one of the large computers of the 60's. Nelson also developed a project called Xanadu, a global system for online hypertext publishing and commerce.
1989 - Tim Berners-Lee and Robert Calliau while working at CERN, started developing code for a hypertext server program, over the next two years. They called their system of hyperlinked HTML documents the World Wide Web (WWW).
A hypertext server is a computer that stores files written in hypertext markup language (HTML). HTML is a language that includes a set of codes (tags) attached to text.
Hypertext link (hyperlink) points to another location in the same or another HTML document.
HTML is read by a Web Browser. HTML is based on SGML (Standard Generalized Markup Language).
Web Browser presents HTML documents in an easy-to-read format in its GUI (Graphical User Interface).
The web caught on quickly within the research community, but few folks outside of this community had browser software to use. So, in 1993, Marc Andreesen at University of Illinois wrote Mosaic, the first GUI program that could read HTML and use HTML documents' hyperlinks to navigate from page to page. Mosaic was first web browser that became widely available for PCs.
1994 - Netscape Communications was developed by Andreesen, and James Clark from Silicon Graphics. Their first product was Netscape Navigator, based on Mosaic.
NAPs (network access points) - maintain the core operations (backbone of Internet). NAPs do not offer direct connections to small companies or to individual people, rather they offer direct connection to companies (ISPs) Internet Service Providers.
ISPs (Internet Service Providers) generally offer more than a connection to the Internet. They usually provide their software, a browser, e-mail service, ftp and other types of services.
Bandwidth is the amount of data that can travel through a communications circuit in one second. Bandwidth depends on several variables, the speed of your modem, and the type of connection your ISP has to the Internet. The narrowest bandwidth rules. In other words, you have a 33.3 Modem and you connect to an ISP that has a T3 connection, your bandwidth will be 33K.
Connection Lines:
POTS (plain old telephone service) which provides usually between 28.8 - 56 Kbps.
DSL (digital subscriber line (loop)) technology developed ISDN (integrated services digital network). ISDN offers upto 128 Kbps.
ISDN integrated services digital network, an international communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second). Most ISDN lines offered by telephone
companies give you two lines at once, called B channels. You can use one line for voice and the other for data, or you can use both lines for data to give you data rates of 128 Kbps, three times the data rate provided by today's fastest modems.
The original version of ISDN employs baseband transmission. Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables and is not widely available.ASDL short for asymmetric digital subscriber line, a new technology that allows
more data to be sent over existing copper telephone lines (POTS). ADSL
supports data rates of from 1.5 to 9 Mbps when receiving data (known as the
downstream rate) and from 16 to 640 Kbps when sending data (known as the
upstream rate).
ADSL requires a special ADSL modem. It is not currently available to the
general public except in trial areas, but many believe that it will be one of the
more popular choices for Internet access over the next few years.
The ITU is currently defining an xDSL standard based on ADSL, called
G.dmt.T1 dedicated phone connection supporting data rates of 1.544Mbits per
second. A T-1 line actually consists of 24 individual channels, each of which
supports 64Kbits per second. Each 64Kbit/second channel can be configured
to carry voice or data traffic. Most telephone companies allow you to buy just
some of these individual channels, known as fractional T-1 access.
T-1 lines are a popular leased line option for businesses connecting to the
Internet and for Internet Service Providers (ISPs) connecting to the Internet
backbone. The Internet backbone itself consists of faster T-3 connections.
T-1 lines are sometimes referred to as DS1 lines.T3 A dedicated phone connection supporting data rates of about 43 Mbps. A T-3 line actually consists of 672 individual channels, each of which supports 64 Kbps.
T-3 lines are used mainly by Internet Service Providers (ISPs) connecting to the Internet backbone and for the backbone itself.
T-3 lines are sometimes referred to as DS3 lines.
ATM (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 older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line.
Current implementations of ATM support data transfer rates of from 25 to 622 Mbps (megabits per second). This compares to a maximum of 100 Mbps for Ethernet, the current technology used for most LANs.
Some people think that ATM holds the answer to the Internet bandwidth problem, but others are skeptical. ATM creates a fixed channel, or route, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic.
When purchasing ATM service, you generally have a choice of four different types of service:
Methods of Connection:
Modem is short for Modulation and Demodulation.
Acronym for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over telephone lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms.
Fortunately, there is one standard interface for connecting external modems to computers called RS-232. Consequently, any external modem can be attached to any computer that has an RS-232 port, which almost all personal computers have. There are also modems that come as an expansion board that you can insert into a vacant expansion slot. These are sometimes called onboard or internal modems.
While the modem interfaces are standardized, a number of different protocols for formatting data to be transmitted over telephone lines exist. Some, like CCITT V.34, are official standards, while others have been developed by private companies. Most modems have built-in support for the more common protocols -- at slow data transmission speeds at least, most modems can communicate with each other. At high transmission speeds, however, the protocols are less standardized.
Aside from the transmission protocols that they support, the following characteristics distinguish one modem from another:
To get the most out of a modem, you should have a communications software package, a program that simplifies the task of transferring data.
Communications Protocols
ProtocolMaximum Transmission Rate
Duplex ModeBell 103 300 bps Full CCITT V.21 300 bps Full Bell 212A 1,200 bps Full ITU V.22 1,200 bps Half ITU V.22bis 2,400 bps Full ITU V.29 9,600 bps Half ITU V.32 9,600 bps Full ITU V.32bis 14,400 bps Full ITU V.34 36,600 bps Full ITU V.90 56,000 bps Full
Analog moves continuously. Telephone lines are considered analog lines.
Almost everything in the world can be described or represented in one of two forms: analog or digital. The principal feature of analog representations is that they are continuous. In contrast, digital representations consist of values measured at discrete intervals.
Digital watches are called digital because they go from one value to the next without displaying all intermediate values. Consequently, they can display only a finite number of times of the day. In contrast, watches with hands are analog, because the hands move continuously around the clock face. As the minute hand goes around, it not only touches the numbers 1 through 12, but also the infinite number of points in between.
Early attempts at building computers used analog techniques, but accuracy and reliability were not good enough. Today, almost all computers are digital.
Digital
Describes any system based on discontinuous data or events. Computers are digital machines because at their most basic level they can distinguish between just two values, 0 and 1, or off and on. There is no simple way to represent all the values in between, such as 0.25. All data that a computer processes must be encoded digitally, as a series of zeroes and ones.
The opposite of digital is analog. A typical analog device is a clock in which the hands move continuously around the face. Such a clock is capable of indicating every possible time of day. In contrast, a digital clock is capable of representing only a finite number of times (every tenth of a second, for example).
In general, humans experience the world analogically. Vision, for example, is an analog experience because we perceive infinitely smooth gradations of shapes and colors. Most analog events, however, can be simulated digitally. Photographs in newspapers, for instance, consist of an array of dots that are either black or white. From afar, the viewer does not see the dots (the digital form), but only lines and shading, which appear to be continuous. Although digital representations are approximations of analog events, they are useful because they are relatively easy to store and manipulate electronically. The trick is in converting from analog to digital, and back again.
This is the principle behind compact discs (CDs). The music itself exists in an analog form, as waves in the air, but these sounds are then translated into a digital form that is encoded onto the disk. When you play a compact disc, the CD player reads the digital data, translates it back into its original analog form, and sends it to the amplifier and eventually the speakers.
Internally, computers are digital because they consist of discrete units called bits that are either on or off. But by combining many bits in complex ways, computers simulate analog events. In one sense, this is what computer science is all about.
Note: Converting a digital signal to analog signal is modulation and converting an analog signal to a digital signal is demodulation.
If you are connecting a modem to the Internet, you will need to make sure you have software that will implement TCP/IP settings.
TCP/IP Abbreviation for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.
SLIP (serial line Internet protocol) is a method of connecting to the Internet. Another more common method is PPP (Point-to-Point Protocol). SLIP is an older and simpler protocol, but from a practical perspective, there's not much difference between connecting to the Internet via SLIP or PPP. In general, service providers offer only one protocol although some support both protocols.
PPP (point-to-point protocol) is a method of connecting a computer to the Internet. PPP is more stable than the older SLIP protocol and provides error checking features.
