Unit 3: Introduction to Internet PDF

Unit 3: Introduction to Internet What is the Internet? Internet is a global network that connects billions of computers across the world with each other and to the World Wide Web. It uses standard internet protocol suite (TCP/IP) to connect billions of computer users worldwide. It is set up by usi...

Unit 3: Introduction to Internet What is the Internet? Internet is a global network that connects billions of computers across the world with each other and to the World Wide Web. It uses standard internet protocol suite (TCP/IP) to connect billions of computer users worldwide. It is set up by using cables such as optical fibers and other wireless and networking technologies. At present, internet is the fastest mean of sending or exchanging information and data between computers across the world. It is believed that the internet was developed by "Defense Advanced Projects Agency" (DARPA) department of the United States. And, it was first connected in 1969. Why is the Internet Called a Network? Internet is called a network as it creates a network by connecting computers and servers across the world using routers, switches and telephone lines, and other communication devices and channels. So, it can be considered a global network of physical cables such as copper telephone wires, fiber optic cables, tv cables, etc. Furthermore, even wireless connections like 3G, 4G, or Wi-Fi make use of these cables to access the Internet. Internet is different from the World Wide Web as the World Wide Web is a network of computers and servers created by connecting them through the internet. So, the internet is the backbone of the web as it provides the technical infrastructure to establish the WWW and acts as a medium to transmit information from one computer to another computer. It uses web browsers to display the information on the client, which it fetches from web servers. History of the Internet The forerunner of the Internet, the ARPANet, went live for the first time in 1969. The TCP/IP, open networking protocol suite, was adopted by the ARPANet in 1983, and the National Science Foundation Network (NSFN) developed the network to link university computer science departments across the US in 1985. When the hypertext transfer protocol (HTTP) was developed in 1989, it enabled different computer platforms to connect to the same Internet sites, which dramatically improved communications over the network. The Mosaic Web browser was developed in 1993. Over the years of its existence, the Internet has remained a constant growth and development. For instance, IPv6 was created to provide for a significant future rise in the number of IP addresses that could be used. In a related development, the Internet of Things (IoT) refers to the rapidly developing environment where nearly any entity or device can be given a unique identifier (UID) and the capability to communicate data automatically over the Internet. Working of Internet When you turn on your computer and type a domain name in the browser search bar, your browser sends a request to the DNS server to get the corresponding IP address. After getting the IP address, the browser forwards the request to the respective server. Once the server gets the request to provide information about a particular website, the data starts flowing. The data is transferred through the optical fiber cables in digital format or in the form of light pulses. As the servers are placed at distant places, the data may have to travel thousands of miles through optical fiber cable to reach your computer. The optical fiber is connected to a router, which converts the light signals into electrical signals. These electrical signals are transmitted to your laptop using an Ethernet cable. Thus, you receive the desired information through the internet, which is actually a cable that connects you with the server. Furthermore, if you are using wireless internet using wifi or mobile data, the signals from the optical cable are first sent to a cell tower and from where it reaches to your cell phone in the form of electromagnetic waves. The internet is managed by ICANN (Internet Corporation for Assigned Names and Numbers) located in the USA. It manages IP addresses assignment, domain name registration, etc. Uses of the internet Generally speaking, the Internet may be used to exchange information with people all over the world, communicate across great distances, and locate information or answers fast on almost any subject. Here are some examples of specific uses for the Internet: o Using social media and content sharing. o Instant messaging, video conferencing, Internet Relay Chat (IRC), Internet telephony, and email are all examples of electronic communication. These all are used through the Internet. o Access to online degree programs, courses, and workshops for education and self-improvement. o Searching for jobs: To advertise available positions, submit job applications, and hire candidates identified on social networking sites like LinkedIn, both employers and applicants use the Internet. Applications of Internet Here are the top 10 applications of Internet are: 1. Communication 2. Web Browsing 3. Online Shopping 4. Real-Time Update 5. Social Media 6. Job Search 7. Education 8. Travel 9. Stock Market Update 10. Video Conferencing 1.Communication Communication refers to exchanging ideas and thoughts between or among people to create understanding. The communication process involves the elements of source, encoding, channel, receiver, decoding, and feedback. In organizations, both formal and informal communications simultaneously take place. Formal communications refer to official communications in orders, notes, circulars, agenda, minutes, etc. Apart from formal communications, informal grapevine communications also exist. Informal communications are usually in the form of rumors, whispers, etc. They are unofficial, unrecorded, and spread very fast. 2. Web Browsing Web Browsing is one of the applications of the internet. A web browser is a program that helps the user to interact with all the data in the WWW (World Wide Web). There are many web browsers present in today's world. Some of them are as follows: Google Chrome Firefox Safari Internet Explorer Opera Microsoft Edge Netscape 3. Online Shopping The era of the internet took shopping into a new market concept, where many virtual shops are available 24x7. The shops provide all the necessary details of a product on their website, so the user can choose as per their needs. 4. Real-Time Update The internet makes things easier. One can quickly get an update on the things happening in real-time in any part of the world. For example, sports, politics, business, finance, etc. The internet is very useful in many decisions based on real-time updates. 5. Social Media The youth of this generation spend the maximum of their free time on social media, all thanks to the internet. Social media is a place where the user can communicate with anyone, like friends, family, classmates, etc. User can promote their businesses on social media as well. You can also post your thoughts, pictures and videos with your friends on social media. 6. Job Search The internet has brought a revolution in the field of Jobs. The candidate can search for their dream job, apply and get it very easily. Even companies nowadays post their need on the internet and hire candidates as per their skills based on the job role. There are many platforms which are primarily doing this. Some of them are listed below.  LinkedIn Monster.com Naukari.com Indeed Glassdoor Upwork 7. Education The Internet has a vital role in the education field. It became an effective tool in both teaching and learning. Teachers can upload their notes or learning videos on the websites with the help of the internet. It made the learning process more diverse and joyful. 8. Travel Users can easily search for their favourite tourist places worldwide and plan their trips. One can book holiday trips, cabs, hotels, flight tickets, clubs, etc., with the help of the Internet. Some websites that provide these facilities are as follows: goibibo.com makemytrip.com olacabs.com 9. Stock Market Update A stock market update refers to the latest information and news related to the financial markets, particularly the stock market. The stock market is where individuals buy and sell publicly traded company shares. Stock market updates include vital data and statistics, like the current prices of major stocks, individual stock prices, trading volumes, market capitalization, and price movements. 10. Video Conferencing Video conferencing means using computers to provide a video link between two or more people. It allows users in different locations to hold face-to-face meetings. You can also see them instead of just talking to someone on the telephone. Video conferencing is a widely accepted mode of communication among businesses, houses, and other organizations. Introduction Computer Network o Computer Network is a group of computers connected with each other through wires, optical fibres or optical links so that various devices can interact with each other through a network. o The aim of the computer network is the sharing of resources among various devices. o In the case of computer network technology, there are several types of networks that vary from simple to complex level. Computer Network Types A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications. A computer network can be categorized by their size. A computer network is mainly of four types: o LAN(Local Area Network) o PAN(Personal Area Network) o MAN(Metropolitan Area Network) o WAN(Wide Area Network) LAN(Local Area Network) o Local Area Network is a group of computers connected to each other in a small area such as building, office. o LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. o It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables. o The data is transferred at an extremely faster rate in Local Area Network.  o Local Area Network provides higher security. PAN(Personal Area Network) o Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters. o Personal Area Network is used for connecting the computer devices of personal use is known as Personal Area Network. o Thomas Zimmerman was the first research scientist to bring the idea of the Personal Area Network. o Personal Area Network covers an area of 30 feet. o Personal computer devices that are used to develop the personal area network are the laptop, mobile phones, media player and play stations. There are two types of Personal Area Network: o Wired Personal Area Network o Wireless Personal Area Network Wireless Personal Area Network: Wireless Personal Area Network is developed by simply using wireless technologies such as WiFi, Bluetooth. It is a low range network. Wired Personal Area Network: Wired Personal Area Network is created by using the USB. MAN(Metropolitan Area Network) o A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. o Government agencies use MAN to connect to the citizens and private industries. o In MAN, various LANs are connected to each other through a telephone exchange line. o The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc. o It has a higher range than Local Area Network(LAN). Uses Of Metropolitan Area Network: o MAN is used in communication between the banks in a city. o It can be used in an Airline Reservation. o It can be used in a college within a city. o It can also be used for communication in the military. WAN(Wide Area Network) o A Wide Area Network is a network that extends over a large geographical area such as states or countries. o A Wide Area Network is quite bigger network than the LAN. o A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fibre optic cable or satellite links. o The internet is one of the biggest WAN in the world.  o A Wide Area Network is widely used in the field of Business, government, and education. Network Topology Topology defines the structure of the network of how all the components are interconnected to each other. There are two types of topology: physical and logical topology. Types of Network Topology Physical topology is the geometric representation of all the nodes in a network. There are six types of network topology which are Bus Topology, Ring Topology, Tree Topology, Star Topology, Mesh Topology, and Hybrid Topology. 1) Bus Topology o The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable.  o Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable. o When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not. o The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks. o The configuration of a bus topology is quite simpler as compared to other topologies. o The backbone cable is considered as a "single lane" through which the message is broadcast to all the stations. o The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access). CSMA: It is a media access control used to control the data flow so that data integrity is maintained, i.e., the packets do not get lost. There are two alternative ways of handling the problems that occur when two nodes send the messages simultaneously. o CSMA CD: CSMA CD (Collision detection) is an access method used to detect the collision. Once the collision is detected, the sender will stop transmitting the data. Therefore, it works on "recovery after the collision". o CSMA CA: CSMA CA (Collision Avoidance) is an access method used to avoid the collision by checking whether the transmission media is busy or not. If busy, then the sender waits until the media becomes idle. This technique effectively reduces the possibility of the collision. It does not work on "recovery after the collision". Advantages of Bus topology: o Low-cost cable: In bus topology, nodes are directly connected to the cable without passing through a hub. Therefore, the initial cost of installation is low. o Moderate data speeds: Coaxial or twisted pair cables are mainly used in bus-based networks that support upto 10 Mbps. o Familiar technology: Bus topology is a familiar technology as the installation and troubleshooting techniques are well known, and hardware components are easily available. o Limited failure: A failure in one node will not have any effect on other nodes. Disadvantages of Bus topology: o Extensive cabling: A bus topology is quite simpler, but still it requires a lot of cabling.  o Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes. o Signal interference: If two nodes send the messages simultaneously, then the signals of both the nodes collide with each other. o Reconfiguration difficult: Adding new devices to the network would slow down the network. o Attenuation: Attenuation is a loss of signal leads to communication issues. Repeaters are used to regenerate the signal. 2) Ring Topology o Ring topology is like a bus topology, but with connected ends. o The node that receives the message from the previous computer will retransmit to the next node. o The data flows in one direction, i.e., it is unidirectional. o The data flows in a single loop continuously known as an endless loop. o It has no terminated ends, i.e., each node is connected to other node and having no termination point. o The data in a ring topology flow in a clockwise direction. o The most common access method of the ring topology is token passing. o Token passing: It is a network access method in which token is passed from one node to another node. o Token: It is a frame that circulates around the network. Advantages of Ring topology: o Network Management: Faulty devices can be removed from the network without bringing the network down. o Product availability: Many hardware and software tools for network operation and monitoring are available.  o Cost: Twisted pair cabling is inexpensive and easily available. Therefore, the installation cost is very low. o Reliable: It is a more reliable network because the communication system is not dependent on the single host computer. Disadvantages of Ring topology: o Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes. o Failure: The breakdown in one station leads to the failure of the overall network. o Reconfiguration difficult: Adding new devices to the network would slow down the network. o Delay: Communication delay is directly proportional to the number of nodes. Adding new devices increases the communication delay. 3) Star Topology o Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer. o The central computer is known as a server, and the peripheral devices attached to the server are known as clients. o Coaxial cable or RJ-45 cables are used to connect the computers. o Hubs or Switches are mainly used as connection devices in a physical star topology. o Star topology is the most popular topology in network implementation. Advantages of Star topology o Efficient troubleshooting: Troubleshooting is quite efficient in a star topology as compared to bus topology. In a bus topology, the manager has to inspect the kilometers of cable. In a star topology, all the stations are  connected to the centralized network. Therefore, the network administrator has to go to the single station to troubleshoot the problem. o Network control: Complex network control features can be easily implemented in the star topology. Any changes made in the star topology are automatically accommodated. o Limited failure: As each station is connected to the central hub with its own cable, therefore failure in one cable will not affect the entire network. o Familiar technology: Star topology is a familiar technology as its tools are cost-effective. o Easily expandable: It is easily expandable as new stations can be added to the open ports on the hub. o Cost effective: Star topology networks are cost-effective as it uses inexpensive coaxial cable. o High data speeds: It supports a bandwidth of approx 100Mbps. Ethernet 100BaseT is one of the most popular Star topology networks. Disadvantages of Star topology o A Central point of failure: If the central hub or switch goes down, then all the connected nodes will not be able to communicate with each other. o Cable: Sometimes cable routing becomes difficult when a significant amount of routing is required. 4) Tree topology o Tree topology combines the characteristics of bus topology and star topology. o A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion. o The top-most node in tree topology is known as a root node, and all other nodes are the descendants of the root node.  o There is only one path exists between two nodes for the data transmission. Thus, it forms a parent-child hierarchy. Advantages of Tree topology o Support for broadband transmission: Tree topology is mainly used to provide broadband transmission, i.e., signals are sent over long distances without being attenuated. o Easily expandable: We can add the new device to the existing network. Therefore, we can say that tree topology is easily expandable. o Easily manageable: In tree topology, the whole network is divided into segments known as star networks which can be easily managed and maintained. o Error detection: Error detection and error correction are very easy in a tree topology. o Limited failure: The breakdown in one station does not affect the entire network. o Point-to-point wiring: It has point-to-point wiring for individual segments. Disadvantages of Tree topology o Difficult troubleshooting: If any fault occurs in the node, then it becomes difficult to troubleshoot the problem. o High cost: Devices required for broadband transmission are very costly. o Failure: A tree topology mainly relies on main bus cable and failure in main bus cable will damage the overall network. o Reconfiguration difficult: If new devices are added, then it becomes difficult to reconfigure. 6) Hybrid Topology o The combination of various different topologies is known as Hybrid topology. o A Hybrid topology is a connection between different links and nodes to transfer the data. o When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology. For example, if there exist a ring topology in one branch of ICICI bank and bus topology in another branch of ICICI bank, connecting these two topologies will result in Hybrid topology. Advantages of Hybrid Topology o Reliable: If a fault occurs in any part of the network will not affect the functioning of the rest of the network. o Scalable: Size of the network can be easily expanded by adding new devices without affecting the functionality of the existing network. o Flexible: This topology is very flexible as it can be designed according to the requirements of the organization.  o Effective: Hybrid topology is very effective as it can be designed in such a way that the strength of the network is maximized and weakness of the network is minimized. Disadvantages of Hybrid topology o Complex design: The major drawback of the Hybrid topology is the design of the Hybrid network. It is very difficult to design the architecture of the Hybrid network. o Costly Hub: The Hubs used in the Hybrid topology are very expensive as these hubs are different from usual Hubs used in other topologies. o Costly infrastructure: The infrastructure cost is very high as a hybrid network requires a lot of cabling, network devices, etc. Introduction to TCP/IP TCP/IP stands for Transmission Control Protocol/Internet Protocol and is a suite of communication protocols used to interconnect network devices on the internet. TCP/IP is also used as a communications protocol in a private computer network -- an intranet or extranet. The entire IP suite -- a set of rules and procedures -- is commonly referred to as TCP/IP. TCP and IP are the two main protocols, though others are included in the suite. The TCP/IP protocol suite functions as an abstraction layer between internet applications and the routing and switching fabric. TCP/IP specifies how data is exchanged over the internet by providing end-to- end communications that identify how it should be broken into packets, addressed, transmitted, routed and received at the destination. TCP/IP requires little central management and is designed to make networks reliable with the ability to recover automatically from the failure of any device on the network. Other components in a TCP/IP network Other components present in a TCP/IP network include subnet masks, network address translation (NAT) and various protocols. A subnet mask tells a computer, or other network device, what portion of the IP address is used to represent the network and what part is used to represent hosts, or other computers, on the network. A NAT is the virtualization of IP addresses. It helps improve security and decrease the number of IP addresses an organization needs. Common TCP/IP protocols include the following: Hypertext Transfer Protocol. HTTP handles the communication between a web server and a web browser. HTTP Secure. HTTP Secure handles secure communication between a web server and a web browser. File Transfer Protocol. FTP handles transmission of files between computers. Domain name system. DNS translates domain names into IP addresses. Simple mail transfer protocol. SMTP is used for email communications and is responsible for the transmission of emails between mail servers. User datagram protocols. UDP is a connectionless protocol that offers faster but less dependable data delivery. It's widely used in real-time applications such as video streaming and online gaming. How does TCP/IP work? TCP/IP uses the client-server model of communication in which a user or machine -- a client -- is provided a service, such as sending a webpage, by another computer -- a server -- in the network. Collectively, the TCP/IP suite of protocols is classified as stateless, which means each client request is considered new because it's unrelated to previous requests. Being stateless frees up network paths so they can be used continuously. The transport layer itself, however, is stateful. It transmits a single message and its connection remains in place until all the packets in a message have been received and reassembled at the destination. The TCP/IP model differs slightly from the seven-layer OSI networking model designed after it. The OSI reference model defines how applications can communicate over a network. The 4 layers of the TCP/IP model TCP/IP functionality is divided into the following four layers, each of which includes specific protocols: 1. Application layer. The application layer is the top layer and provides applications with standardized data exchange. Its protocols include HTTP, FTP, Post Office Protocol 3 (POP3), SMTP, DNS, Dynamic Host Configuration Protocol and SNMP. At the application layer, the payload is the actual application data. 2. Transport layer. The transport layer is responsible for maintaining end-to- end communications across the network. TCP handles communications between hosts and provides flow control, multiplexing and reliability. The transport protocols include TCP and User Datagram Protocol (UDP), which is sometimes used instead of TCP for special purposes. 3. Internet layer. The internet layer, also called the network layer, deals with packets and connects independent networks to transport the packets across network boundaries. The network layer protocols are IP and Internet Control Message Protocol, which are used for error reporting. 4. Network link layer. The network link layer, also known as the network interface layer or data link layer, consists of protocols that operate only on a link -- the network component that interconnects nodes or hosts in the network.