0In this arrangement, all of Company A's customers can talk to each other, and all of Company B's customers can talk to each other, but there is no way for Company A's customers and Company B's customers to intercommunicate. Therefore, Company A and Company B both agree to connect to NAPs in various cities, and traffic between the two companies flows between the networks at the NAPS.
In the real Internet, dozens of large Internet providers interconnect at NAPs in various cities, and trillions of bytes of data flow between the individual networks at these points. The Internet is a collection of huge corporate networks that agree to all intercommunicate with each other at the NAPs. In this way, every computer on the Internet connects to every other.
funny one liner about the Internet goethe and you feed him for a day; teach him to use the Internet and he won't bor you for months.
An exercise started by the United States Department of Defense way ba in the 1960s has become one of the most amazing technological and soci accomplishments of mankind. Millions of people across the globe are using bo this complex, interconnected network of computers for research, information communication and commercial interests. In this unit, you will learn about the computer networks and the Internet, which forms the basic technology structure and establishes a strong foundation that underlies all electronic business. You will also learn about connectivity technologies and communication protocols.
THE INTERNET
The Internet is a worldwide collection of computer networks, cooperating with each other to exchange data using a common software standard. In simple language, the Internet is a worldwide network of thousands of computers and computer networks. Millions of people use the Internet every day, but only a small percentage of them really understand what the Internet is and how it works. This large system of interconnected computer networks that spans the globe, allows you to communicate with other people throughout the world by means of electronic mail, online newspapers, magazines, chat, download software, buy products and much, much more. Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks. Technically, what distinguishes the Internet is its use of a set of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol).
Many a times you may be confused between the Internet and the World o Wide Web (WWW) and feel that they are the one and the same. But they are not. The Internet is to the World Wide Web what Europe is to France. One is the container; the other is an item within the container, And along with WWW, the Internet also contains many other sub-networks or protocols like HTTP, e-mail, FTP, Instant Messenger, P2P, Telnet etc.Who owns the Internet?
Nobody "owns" the Internet everybody owns "their" piece of the Internet.
Today, the Internet is a public, cooperative and self-sustaining facility accessible to hundreds of millions of people worldwide. No one actually owns the Internet, and no single person or organisation controls the Internet in its entirety. More of a concept than an actual tangible entity, the Internet relies on a physical infrastructure that connects networks to other networks. There are many organisations, corporations, governments, schools, private citizens and service providers that all own pieces of the infrastructure, but there is no single body that owns it all.
The obvious doubt that might come to your mind is, "How does the entire system work if no one owns or controls it?"
There are organisations that oversee and standardise what happens on the Internet and they assign IP addresses and domain names. A few such organisations are the National Science Foundation (NSF), Internet Corporation for Assigned Names and Numbers (ICANN) and InterNIC. 1.3 THE BEGINNING OF THE INTERNET
The Internet was conceived by the Advanced Research Projects Agency (ARPA) of the US Military in 1969 and was first known as the ARPANET. The original aim was to create a network that would allow users of a research computer at one university to be able to "talk to" research computers at other universities. This was also to be a military research network that could survive a nuclear strike, decentralised so that if any locations (cities) in the U.S. were attacked, the military could still have control of their nuclear arms for a counter- attack.
The First Node on the Internet
Under the research being carried out at ARPANET and research universities, the first node on the Internet called 'Interface Message Processor (IMP)' was setup at the University of California, Los Angeles. First Interface Message Processor (IMP)
Four nodes were later set up at UCLA, Stanford, University of California at Santa Barbara and the University of Utah.
To test the idea, they set up an IMP at each location and had the IMP al UCLA call the IMP at Stanford. Once the connection was established, researchers made a phone call to the people at UCLA and began to send a simple text string to the Stanford IMP. For lack of a better term, everyone agreed they would type in "LOGIN" and see if the computer at Stanford would display the information properly. This was the dialogue that took place:
Charlie Klein, an undergraduate at UCLA and an assistant on the project, took the phone and typed the letter L on his terminal.
"Did you get the L?" he asked.
"Yes," came the reply from Stanford. Klein then typed the letter O.
"Do you see the O?" he asked.
"Yes, we see the O," replied the Stanford team.
Klein typed in the G, and the system crashed!!! The researchers for a brief moment had a glimpse of our Internet future- logins, crashes, and all!! Thus, the Internet began as a computer network of ARPANET that linked computer networks at several universities and research laboratories in the United States.
In 1974, TCP/IP (Transmission Control Protocol/Internet Protocol), the protocol used on the Internet was developed. This Internet Protocol is the fundamental software employed to control the Internet. This protocol specifies how data is routed from one computer to the other. The Transmission Control Protocol verifies whether or not the information arrived at the designated computer, and if not, makes sure that the information is sent again. Stanford University was one of a few sites of early Internet development where Vincent Cerf and his colleagues researched and developed the communication protocols that would later be used for transmitting information across the Internet. Cerf's pioneering contributions to network technology earned him the title 'Father of the Internet'. This project was also sponsored by the United States Department of Defense and the Advanced Research Projects Agency (ARPA).
During the early years of the 1980s, the Internet became more popular as more sites were added to ARPANET. Even though the ARPANET had shut down by 1984, the usage of the Internet was spreading. The Internet was transferred from the ARPANET to the National Science Foundation (NSF). By this year an estimation of 500 computers were 'connected' (using the Internet).
The Early Internet
The Internet was completely textual and in black and white. All tasks had to be done by using commands of computer language, such as UNIX, developed by Bell Laboratories in 1972. Users actually had to learn computer language commands to be able to use the Internet unless they possessed certain computer skills. The use of networks was still limited only to those groups of people from research and academic communities who could access those and were developing many creative applications. Between 1979 and 1989, these network applications were further improved and tested by an increasing number of users.
The explosion of personal computer use during the 1980s also helped more people become comfortable with computers. In the late 1980s, these independent academic and research networks merged into what we now call the Internet.
The Early Applications of the Internet
The main goal of the US Military was to use the Internet for academic research and military research, but the power of this network was soon unleashed during 1970 and 1980. The earliest application of the Internet, e-mail, was born in 1972 when Ray Tomlinson, a Cambridge, USA, computer scientist addressed the first e-mail to himself and was supposed to have contained the message "QWERTYIOP". He used the "@" to distinguish between the sender's name and the network name in the e-mail address and became the man who will be always remembered in history as the man who picked @ as the locator symbol in electronic addresses. Thus, Ray Tomlinson became the inventor of e-mail, the application that launched the digital information revolution.
connection, after e-mail it was considered a connection between another. The National Science Foundation (NSF) was eventually in designing an expanded network that became the basis of the Internet as it in known today. Millions of computers worldwide connected via a vast network that consists of tens of thousands of interconnected sub-networks with no single owner. But it still lacked a personal touch, as accessing information was not user friendly. omputer instrumental
While the Internet was in the later stage of development in late 1990, Tim Berners-Lee and a group of scientists in the European Laboratory of Particle Physics (CERN) were developing a system for worldwide interconnectivity that later became known as the World Wide Web (WWW). They said that the WWW "was developed to be a pool of human knowledge, which would allow collaborators in remote sites to share their ideas and all aspects of a common project". Tim Berners-Lee's effort in web development gave him the title "Father of the World Wide Web".
Tim Berners-Lee invented the World Wide Web, defining HTML (hypertext markup language), HTTP (HyperText Transfer Protocol) and URLs (Universal Resource Locators).
The Web is based on hypertext, which permits the user to connect from one document to another at different sites on the Internet via hyperlinks (specially programmed words, phrases, buttons, or graphics). Unlike other Internet protocols, such as FTP and e-mail, the Web is accessible through a graphical user interface (GUI). This helped the Internet to get user-friendly and it no longer remained a tool to be used by just scientists and researchers but reached the common man.
The Commercial Internet
The National Science Foundation (NSF) still prohibited commercial network traffic on its networks. As personal computers became more powerful, affordable and available, corporate companies increasingly used them to construct their own internal networks. Although these networks included e-mail software that employees could use to send messages to each other, businesses wanted their employees to be able to communicate with people outside their corporate networks.
In 1989, the NSF permitted two commercial e-mail services, MCI Mail and CompuServe, to establish limited connections to the Internet. These commercial providers allowed their subscribers to exchange e-mail messages with members of the academic and research communities who were connected to the Internet. These connections allowed commercial enterprises to send e-mail directly to Internet addresses and allowed members of research and education communities on the Internet to send e-mail directly to MCI Mail and CompuServe addresses. The NSF justified this limited commercial use of the Internet as a service that would primarily benefit the Internet's noncommercial users. In 1991, the NSF eased its restrictions on the Internet commercial activity
Computer Networks have rapidly become an integral part of business li They allow a business to streamline the overall operation and to interact w suppliers and customers very efficiently.
In many cases computer networks are seen as the solution to every proble within business, and to some extent - the magic wand to tackle all problems wi
By understanding the different kinds of networks and how they work you will be able to determine which network will suit your organisation's need best. Some networks are rather simple and easy to set up while others are much more complex and will require the help of a trained professional.
Whilst it is not necessary to understand fully the technical details, it i necessary to understand in full what precise purpose the introduction of a compute network into an organisation serves. This is crucial for the project to be accepte by the staff and to help the technicians to design the network accordingly.
Computer Networks Classification
Computer Networks are classified according to the distance between individual computers that are attached to the network. The classification includes the following:
LANs: Local Area Network, a computer network that spans a distance of tens of metres at the most. LANs are very common in offices but can also connect several offices together.
There is no limit as to how many computers are networked for the network to be classified as LAN.
WANs: Wide Area Network, a computer network that spans hundreds of metres to a few kilometres. Typically, a campus spanning network that connects different departments in any University or a larger company is called a WAN.
MANS: Metropolitan Area Network, in essence a computer network that is meant to span a whole metropolitan area. This concept was very popular in the early 1990s when various cities envisaged establishing such networks. In practice these networks are very rare, and today only the concept survives. This is mainly due to the increasingly private providers that develop networks as opposed to cities and councils taking the development of such networks into their own hands.
The above classification is purely based on the size of the area that the network covers.
1.5 TECHNOLOGY OVERVIEW
Notes
With the growth of LANs and WANs a new demand started arising wherein interconnectivity of different networks became extremely crucial for resource sharing. Isolated LANs made electronic communication between different offices or departments impossible. Duplication of resources meant that the same hardware and software had to be supplied to each office or department, as did separate support staff. This lack of network management meant that no centralised method of managing and troubleshooting networks existed.
A new term called Internetwork was soon coined.
An Internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. Internetworking refers to the industry, products, and procedures that meet the challenge of creating and administering Internetworks.
Internetworking evolved as a solution to three key problems: isolated LANs, duplication of resources, and a lack of network management.
1
Activity 2
Write down names of four organisations whose networks can be classified under LAN and WAN.
1.6 PACKET SWITCHED NETWORKS
A packet is a unit of data that is transmitted across a packet-switched network. A packet-switched network is an interconnected set of networks that are joined by routers or switching routers. The most common packet-switching technology is TCP/IP, and the Internet is the largest packet-switched network. Other packet-switched network technologies include X.25 and IPX/SPX (the original Novell NetWare protocols).
The concept of a packet-switched network is that any host computer. connecting to the network can, in theory, send packets to any other host computer. The network is said to provide any-to-any service. The network typically consists of multiple paths to a destination that provide redundancy. Packets contain header information that includes a destination address. Routers in the network read this address and forward packets along the most appropriate path to that destination.
Packets have a header and a data area. The header holds the address and routing information. Think of a packet as an envelope in which the destination address is written on the outside of the envelope and data goes inside,
A single transmission may require hundreds or thousands of packets. For example, a large file is broken up into many small pieces that are inserted in the payload area of packets.
1.7 INTERNET PROTOCOLS
(Intern
The Internet protocols are the world's most popular open-system (nonproprietary) protocol suite because they can be used to communicate across any set of interconnected networks and are equally well suited for LAN and WAN communications. The Internet protocols consist of a suite of communication protocols, of which the two best known are the Transmission Control Protocol (TCP) and the Internet Protocol (IP). The Internet protocol suite not only includes lower-layer protocols (such as TCP and IP), but it also specifies common applications such as electronic mail, terminal emulation and file transfer. You will get a broad introduction to specifications that comprise the Internet protocols. You will learn IP addressing and key upper-layer protocols used in the Internet.
The global Internet is a success because of TCP/IP. Every computer on the Internet must have a unique address. IP supports unique addresses by way of a hierarchical addressing scheme. An IP address is a unique number that contains two parts: a network address and host address. The network address is used when forwarding packets across interconnected networks. It defines the destination network, and routers along the way know how to forward the packet based on the network address. When the packet arrives at the destination network, the host portion of the IP address identifies the destination host.
IP Addressing
The version of IP that has been in use for the past 20 years on the Internet is Internet Protocol version 4, abbreviated IPv4. It uses a 32-bit number to identify the computers connected to the Internet. This address is called an IP address. Example of an IP address: 202.54.10.1. Computers do all of their internal calculations using a base 2 (or binary) number system in which each digit is either a 0 or 1. IPv4 uses a 32-bit binary number that allows over 4 billion different addresses (231= 4,294,967,296). While the number probably exceeded the world's population when the Internet was initially being developed, the proliferation of personal computers and the development of the web significantly expanded the role of the "mother of all networks". With the boom of networks, PDAs and IP based phones, the demand for IPs increased so immensely that we started falling short of this existing pool of billions of IP addresses. In 1992, the Internet Architecture Board (IAB) began work on a replacement for the current version of IPv4. By 1995 IAB finalised a new version of IP that is referred to as IPv6. It is currently being evaluated as an experimental portion of the Internet. Under IPv6 source and destination, addresses were expanded to 128 bits. It is expected that this IPv6 will overcome all the shortfalls of IPv4 and also make a considerable technology advancement in routing operations, but it will be many years before the new protocol moves from an experimental status into production.
Private IP addresses
To overcome this problem of the shortfall of IPs, network engineers have devised a number of stop-gap techniques to stretch the supply of IP addresses. One of the most popular techniques is subnetting, which is the use of reserved private IP addresses within LANs and WANs to provide additional address space. Private IP addresses are a series of IP numbers that are not permitted on packets that travel on the Internet. In subnetting, a computer called a network address translation (NAT) device converts those private IP addresses into normal IP addresses when it forwards packets from those computers to the Internet.
The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private networks (local networks):
10.0.0.0-10.255.255.255
172.16.0.0-172.31.255.255
192.168.0.0-192.168.255.255
These IPs should not be used on the Internet. NAT devices are required to connect private networks to the Internet. The NAT device will have at least one "real" or publicly reachable address, and will route traffic destined for the public Internet through that address.
Private IP addresses also provide a basic form of security as in a typical network configuration of this type; it is not possible for the outside world (Internet) to establish a connection directly to a host using these addresses.
IP Address assigning
Today, IP addresses are assigned by five non-profit organisations called the Regional Internet Registry (RIR). They are the American Registry for Internet Number (ARIN), African Network Information Centre (AfriNIC), the Réseaux IP Européens (RIPE), Regional Latin-American and Caribbean IP Address Registry (LACNIC) and the Asia Pacific Network Information Centre (APNIC). These registries assign and manage IP addresses for various parts of the world. ARIN for North America, AfriNIC for Africa, LACNIC for Latin America and the Caribbean, RIPE for Europe, the Middle East, and central Asia, and APNIC for countries in the Asia-Pacific area. These organisations took over the IP address management tasks from the Internet Assigned Numbers Authority (IANA) which still maintains its role to allocate IP addresses from the pools of unallocated addresses to the RIRs according to the established needs.
1.8 INTERNET SERVICE PROVIDERS
An ISP, called an Internet Service Provider, is a company that provides connectivity options for accessing the Internet and related services. Generally, an ISP charges a monthly access fee to the customers. The customer then has access to the Internet for a limited or unlimited number of hours, although the speed at which this data is transferred varies widely.
The Internet
Notes Connecting to the Internet
You may use many different ways to connect to an ISP, but the simplest way to connect is using your computer, modem and telephone line.
memory. Firstly, you will need to have access to a Personal Computer (PC). The minimum requirements for a PC to establish Internet connection are that it must have a modem, at the very least a 486 processor, 64 MB RAM active 100 MB of hard disk space available, a browser (the software the PC uses to access the Internet), a monitor, a keyboard and a mouse.
Optional equipment includes a printer, a soundcard, speakers, a video camera and a document/ image scanner.
The PC dealer would be the best to advise you of which computer is best suited to your needs in terms of functionality, price and ease of use. The beginner who wants to type letters, send e-mail and surf the web will have different needs than the experienced programmer who wants to design web pages with interactive, cartoon style video clips and to send 200 MB files from here to Chicago.
A modem connects your PC to the Internet using a telephone line. The modem (some PCs have an internal modem already installed), plugs into one of the ports (sockets) usually at the rear or the side of the PC and the customer simply plugs in the phone line.
The customer uses the home telephone line to connect to the Internet, along with the login and password provided by the ISP when they have signed up for a dial-up plan and have the relevant equipment including the software. This is by far the easiest method to connect to the Internet. After your computer dials into the Internet service provider you will hear a dial tone, a series of touch tones, a couple of rings, a click and a series of screeches bouncing back and forth at different pitches. This is called 'handshaking, whereupon your PC and modem are negotiating with the Internet Service Provider's (ISP's) modem. The modems look at the line quality for a moment, they handshake and then they negotiate the very best (data exchange) speed possible at the time.
Accessing the Internet
When you are not connected to the Internet and if you try to open a website
you get an error indicating that the page is not found or connectivity is not established. But as soon as you are connected to the Internet by authenticating your user name and password, the entire Internet Pandora opens in front of you. So there must be something different happening to your computer because of which the Internet is accessible to you.
The ISP assign
Dynamic
Static IPs
As soon as your account is authenticated, the ISP assigns you an IP address from its pool of addresses which becomes your own identity on the Internet till such time that you are connected to the ISP. Thus, you become a part of the Internet and contribute your share of owning the Internet.
The ISP assigns two types of IP addresses:
Dynamic IPs
Static IPs
Dynamic IPs: A dynamic IP address is a number that is assigned to a computer by an Internet service provider to be its temporary address on the Internet. These are the IPs which are allocated to any dial-in user who dials to the ISP's POP (Point Of Presence).
Notes
Dynamic:
temporary
Static:
Static IPs: A static IP address is a number that is assigned to a computer by an Internet service provider to be its permanent address on the Internet. These are the IPs allocated to the machines which are running round the clock and are connected to the Internet and are dedicated machines.
permanent
Internet connectivity options and speeds
The dial-up modem is one of the cheapest and the most common option to connect to the Internet. The other media by which you can connect to the Internet are ISDN, DSL, Cable, Leased Line, Satellite services, RF connectivity, Wi-Fi, Wi-Max connectivity, etc.
Dial-up Modem
The dial-up modem connects at an average speed of 56K or kilobits per second which means 56 thousand bits (0s and 1s) passing through the line per second. But this is a big limitation for some users who need or want a lot of data transferred quickly. Another limitation one usually doesn't receive full 56K access due to line 'noise' static or other interruptions that limit the data through-put. This is particularly common in rural areas. Digital switches and fibre transmission improves line quality, but this requires the replacement of all the wires to your building, and that won't happen overnight. Better performance is possible through higher levels of service and digital transfers.
ISDN/DSL/Cable
Three major types of high speed connectivity have emerged in the last few years and are increasingly available across the country - Integrated Services Digital Network (ISDN), Digital Subscriber Line (DSL) and Cable.
ISDN is like a modem service that involves a dial up, but it uses a high quality line capable of higher performance data transfer up to 256KB/second and higher. It is falling out of favor due to cost and being replaced by the digital services described below.
Improvements in electronic hardware have allowed conventional phone lines to accept data transfers at high rates using the technology called "DSL" or Digital Subscriber Line. At 1.5 megabytes per second, the data transfer rates are almost 50 times faster than the fastest modems. Two 'flavors' of DSL are available, ADSL and SDSL. Of the two, SDSL is the more powerful performer and businesses generally choose it over ADSL. However, any DSL service is only available in larger metropolitan areas so far, as it requires that the phone company or other ISPs to have installed special hardware in their operationalCable companies are offering high performance services the 'modems that link through high speed optical fibre lines. These high spe fibre lines provide an excellent speed and minimum losses. These service require that you have cable connectivity up to your house or office. Genera DSL, or cable connectivity is referred to as Broadband access connectivity.
Leased Lines or Leased Circuits
Leased Line connection, you are directly wired into the Internet i high-speed lines, and you are "online" 24 hours a day, seven days a week These leased line circuits use the existing communication network of telecc companies for providing Internet access.
Leased Line connectivity is great if you are a corporate or a business with a number of users.
Satellite services
This is another category of connectivity that uses satellites as a wireless method and provides the most promise for those in rural areas that need higher capacity, No land infrastructure is needed except the receiver. To provide Internet access using the satellite, you do not need any telephone lines or cable network, but instead you use a satellite dish for two-way data communications It has an upload stream and download stream where upload speed in one-tenth of the download speed. Satellite connection is sometimes unidirectional and is meant for downloading data using the dish antenna, but you are also connected by phone line to the Internet for uploading information.
RF Connectivity
RF is commonly used in the wireless communications industry to describe equipment using radio frequency waves to transmit sounds and data from one point to another. In Internet connectivity, RF equipment is used to transmit data signals using radio waves instead of data cables or telephone lines. Typically you need an antenna on your side as a client antenna and this has to have a clear line of site to the ISP's transmitting tower. Thus, a clear line of site is needed for this connectivity option to work.
Wi-Fi, Wi-Max connectivity
Notes
15
Wi-Fi is the wireless way to handle networking. It is also known as 802.11 networking and wireless networking. The big advantage of Wi-Fi is its simplicity and mobility. You can connect computers anywhere in your home or office without the need for wires. The computers connect to the network using radio signals, and computers can be up to 100 feet or so apart. To establish Internet connectivity using Wi-Fi you need a desktop PC or laptops which are Wi-Fi enabled by installing a Wi-Fi card. To access the Internet using this card you will need to look for a hotspot.
A hotspot is a connection point for a Wi-Fi network. It is a small box that is hardwired into the Internet. The box contains a radio that can simultaneously talk to up to 100 or so Wi-Fi cards. There are many Wi-Fi hotspots now available in public places like restaurants, hotels, libraries and airports. You can also create your own hotspot in your home.
Wi-Max operates similar to Wi-Fi but comes over the problems of speed and distance. Wi-Fi operates up to a maximum distance of 100 feet, but Wi-Max can provide coverage to a very large area as big as 50 km.
Deciding the ISP & the connection speed
Now you may ask 'How am I going to decide how to connect?"
It mostly depends on your budget and the availability of a specific service in your area. This is always changing and due to deregulation, more and more types of businesses can provide you with access services.
The connectivity speed will depend on your usage and the number of people accessing the Internet. Fig. 1.5 shows you a guideline of different speeds and the naming used for each. When you connect to the Internet, your computer becomes part of a network.
Here's an example. Imagine that Company A is a large ISP. In each major city, Company A has a POP. The POP in each city is a rack full of modems that the ISP's customers dial into. Company A leases fibre optic lines from the phone company to connect the POPs together.
Imagine that Company B is a corporate ISP. In each major city Company B also has a POP. Company B builds its own network of fibre optic cables and offers connectivity to all its customers over cable. Company B is such a large company that it runs its own fiber optic lines between its buildings so that they are all interconnected.
In this arrangement, all of Company A's customers can talk to each other, and all of Company B's customers can talk to each other, but there is no way for Company A's customers and Company B's customers to intercommunicate. Therefore, Company A and Company B both agree to connect to NAPs in various cities, and traffic between the two companies flows between the networks at the NAPS.
In the real Internet, dozens of large Internet providers interconnect at NAPs in various cities, and trillions of bytes of data flow between the individual networks at these points. The Internet is a collection of huge corporate networks that agree to all intercommunicate with each other at the NAPs. In this way, every computer on the Internet connects to every other.
