1. Introduction to computer networks.pdf
- 1. MA 619COMPUTERNETWORKS Dr. SONALI CHAKRABORTY DEPARTMENT OF MATHEMATICALAND COMPUTATIONAL SCIENCES NATIONALINSTITUTE OF TECHNOLOGY KARNATAKA SURATHKAL, MANGALORE – 575025, INDIA Dr. Sonali Chakraborty Email: chakrabartysonali@gmail.com 1
- 2. COURSE CONTENTS Dr. Sonali Chakraborty Email: chakrabartysonali@gmail.com 2 ✓ Uses of Computer Network ✓ Network hardware, software , Types of networks, Topology ✓ OSI and TCP/IP Models ✓ Transmission media. Physical Layer. Bit signal transformation, Bit rate control, Multiplexing, Circuit switching, Line coding ✓ Data Link Layer, Data Link Layer Design issues, Addressing, Error correction and detection ✓ Flow control, Medium Access control, Framing, Network Layer Network Layer Design issues , IP addressing, Subnetting ✓ Routing algorithms, IP datagram and fragmentation, Internetworking devices ✓ Transport Layer Transport layer services, Addressing, Connection control, ✓ Congestion control algorithms ✓ Application layer: Application layer protocols SMTP, DNS, FTP, HTTP, ✓ Introduction to Network Security ✓ Introduction to wireless network and Mobile Ad-hoc Networks
- 3. EVALUATION PLAN 3 Dr. Sonali Chakraborty Email: chakrabartysonali@gmail.com 10 Mid- Semester 25% End- Semester 50% Tests 25% Total 100% Reference Books: 1. AS Tannenbaum, Computer Networks, Prentice - Hall 2003. 2. William Stallings, Data and Computer Communication, PHI, 1997 3. James F. Kurose and Keith W Rose, Computer Networking Pearson Education, 2003
- 4. • A computer network is a system of connected devices that can share resources and communicate with each other • It allows computers to access shared information, transfer data, and collaborate • A collection of autonomous computers interconnected by a single technology • Two computers are said to be interconnected if they are able to exchange information • The connection need not be via a copper wire; fiber optics, microwaves, infrared, and communication satellites can also be used • Networks come in many sizes, shapes and forms, as we will see later • They are usually connected together to make larger networks, with the Internet being the most well-known example of a network of networks 4 INTRODUCTION
- 5. USES OF COMPUTER NETWORKS ❑ Business Applications • Consider a company may have a computer for each worker and use them to design products, write brochures, and do the payroll • Initially, some of these computers may have worked in isolation from the others, but at some point, management may have decided to connect them to be able to distribute information throughout the company • The issue here is resource sharing • The goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource or the user Eg. Sharing a printer among a group of employees • More important than sharing physical devices is sharing information such as customer records, product information, inventories, financial statements, tax information etc. • Company’s information system can be visualized as consisting of one or more databases with company information and some number of employees who need to access them remotely
- 6. • The data is stored on powerful computers called servers • Often they are centrally housed and maintained by a system administrator • The employees have simpler machines, called clients, on their desks, with which they access remote data • The client and server machines are connected by a network USES OF COMPUTER NETWORKS CONTD…
- 7. • A computer network can provide a powerful communication medium among employees • Virtually every company that has two or more computers now has email (electronic mail), which employees generally use for a great deal of daily communication • Telephone calls between employees may be carried by the computer network instead of by the phone company • This technology is called IP telephony or Voice over IP (VoIP) when Internet technology is used • Video can be added to audio so that employees at distant locations can see and hear each other as they hold a meeting • This technique is a powerful tool for eliminating the cost and time previously devoted to travel USES OF COMPUTER NETWORKS CONTD…
- 8. • Desktop sharing lets remote workers see and interact with a graphical computer screen • This makes it easy for two or more people who work far apart to read and write a shared blackboard or write a report together • When one worker makes a change to an online document, the others can see the change immediately, instead of waiting several days for a letter • A third goal for many companies is doing business electronically, especially • with customers and suppliers is e-commerce • Airlines, bookstores, and other retailers have discovered that many customers like the convenience of shopping from home • Consequently, many companies provide catalogs of their goods and services online and take orders online • Manufacturers of automobiles, aircraft, and computers, among others, buy subsystems from a variety of suppliers and then assemble the parts USES OF COMPUTER NETWORKS CONTD…
- 9. ❑ Home Applications ▪ Internet access provides home users with connectivity to remote computers ▪ Access to remote information comes in many forms such as surfing the Web for information or just for fun ▪ Information available includes the arts, business, cooking, government, health, history, hobbies, recreation, science, sports, travel, and many others ▪ Keeping newspapers, journals, conference proceedings online ▪ Messaging services ▪ Social Networking ▪ Content creation ▪ Mobile users USES OF COMPUTER NETWORKS CONTD…
- 10. NETWORK HARDWARE • Network hardware has two important dimensions: Transmission technology and Scale • Transmission Technology is used for data communication between sender and receiver • Two types of transmission technology are used in Network Hardware: Point-to- point links and Broadcast links • Point-to-point links: It helps to connect different pairs of machines • There will be one sender and one receiver • The sender and receiver both can act as a client or server simultaneously Example: telephone calls • Broadcast links: In a broadcast network, all the end devices of a network share a common communication channel such that the message sent by any machine can be received by aevery device connected to that network • Radio broadcast and TV broadcast are n example of broadcast networks
- 11. NETWORK HARDWARE CONTD… • Examples of Network Hardware: Server, Client, Router, Switch, Bridge, Firewall, NIC, Cable, Modem, Repeater, and Gateway.
- 12. ❑ Functionalities of Network Hardware: ▪ Server: It is a device that provides services to clients ▪ Client: It is an end device that requests services from servers available on the network ▪ Router: It helps in forwarding the packets over the network by using the store and forward mechanism ▪ Switch: Switch helps to connect devices on a network. It uses the packet switching method to receive, process, and transfer data to the receiver ▪ Bridge: Bridge helps to connect more than one network ▪ Firewall: The purpose of a firewall is to filter out bad packets ▪ NIC: It helps to physically connect the devices to the network. ▪ Cable: It is a medium that helps to connect devices for communication purposes. ▪ Modem: It simply modulates the signal to encode, and demodulate the signal to decode. ▪ Repeater: As the name suggests, the repeater receives a signal and retransmits it, so that the signal can be transmitted over long distances. ▪ Gateway: It is an interface that provides compatibility between networks. It converts protocols, security services, or transfer speeds. NETWORK HARDWARE CONTD…
- 13. • Scale: Distance is an important factor for a network, leading to the use of different types of topologies at various scales • Network Hardware is set up in a network using a scale, and scale may be PAN (Personal Area Network), LAN (Local Area Network), MAN (Metropolitan Area Network), or WAN (Wide Area Network) • PAN can be used when the network hardware is installed on a small scale for example, setting up Wi-Fi or Bluetooth with a mobile or computer is an example of PAN • LAN can be used when network hardware is installed within a 100m to 10km radius. The school network, college network, and office network are examples of LANs • MAN is used when network hardware is set up in a city network • WAN is used for country or global networks NETWORK HARDWARE CONTD…
- 14. NETWORK SOFTWARE • Network Software helps to manage a network and prevents unauthorized access and various cyber-attacks, as by using network software one can restrict access to the network • Network software is embedded in the network hardware like PC, Router, Switch, etc. • Network software such as an operating system helps a computer to act as a server Example of Network Software: Operating System
- 15. NETWORK SOFTWARE CONTD… ❑ Functionalities of Network Software: • Network Software allows a network administrator to set up and install OS • A network administrator can maintain and improve the network using network software • Provides protocols to data upon which communication devices agree and establish successful communication • Network administration can install a network operating system on a computer and make it a server for the network • Network Software provides reliability to the users on a network • The network administrator can remove unauthorized users from a network
- 16. NETWORK TOPOLOGY • Network topology is defined as the physical arrangement through which various endpoints and links in an enterprise network communicate with each other • Organizations use network topology to define how their network nodes are linked to each other. • The structure of a network can directly impact its functioning • Companies must select the most suitable topology for their network to bolster performance and enhance data efficiency • Network topology diagrams allow IT teams to diagnose problems related to connectivity, investigate high latency, and troubleshoot other network issues • The two major categories of topology are physical and logical • Physical network topology refers to the structure of the physical medium for data transmission • On the other hand, logical network topology refers to how the network transmits data between devices, regardless of how these devices are connected physically
- 17. ❑ Point to Point Topology ▪ Simple topology that directly links two nodes and reserves the entire bandwidth of the connection for them to communicate with one another ▪ Physically, point-to-point connections rely on a cable or wire that connects the two endpoints ▪ However, logical topological connections using satellite links and microwaves are more common TYPES OF NETWORK TOPOLOGY Example of a point-to-point connection is changing the temperature of an air conditioning unit using a remote control, Bluetooth file transfer, satellite communication between two ground stations
- 18. ❑ Advantages: ▪ Superior bandwidth, as only two nodes use the link ▪ High speed when compared to other types of network topologies ▪ Simple to implement ▪ Easy to maintain and handle ▪ Low instances of latency ❑ Disadvantages: ▪ Only applicable for small areas with nodes physically close to each other ▪ High dependence on the common link; if the link fails, the network goes down TYPES OF NETWORK TOPOLOGY CONTD…
- 19. ❑ Bus Topology ▪ All the nodes are linked using a single cable with a terminator on both ends. ▪ This configuration sees one main cable acting as the backbone for the whole network. TYPES OF NETWORK TOPOLOGY CONTD… ▪ The server node transmits data from one end of the cable and in a single direction to the client node ▪ As the data travels to each node, its destination address (MAC/IP) is checked to see if it is received and processed ▪ If there is a mismatch in the address, the node does not do anything with the data
- 20. ▪ This way, only the node that recognizes its address uses the data that travels on the single cable, while the other nodes are unaffected ▪ Once the data reaches the end of the cable, the terminator removes it to prevent signal bouncing ❑ Advantages ▪ Easy to add new devices and replace or remove existing devices without affecting other devices connected to the network ▪ Failure in a few devices does not affect other devices, or the network ❑ Disadvantages ▪ Device failure and other network faults are difficult to locate in the network ▪ Damage to the backbone cable can bring the entire network to a halt ▪ Increase in the bandwidth consumption of a few devices can affect the performance of the whole network ▪ Slower operations, as only one node transmits data at a time ▪ Low privacy, as all nodes receive the signal sent by the server TYPES OF NETWORK TOPOLOGY CONTD… This topology follows a half-duplex transmission mode. terminators absorb signals and prevent data reflections
- 21. ❑ Ring Topology ▪ Each node is linked with its neighbor to form a closed network ▪ This configuration sees the data move from one node to another, either unidirectionally or bidirectionally. Such network topology is used in smaller networks TYPES OF NETWORK TOPOLOGY CONTD… • Many ring networks use token passing to regulate data flow • In such an arrangement, a token is transferred from one device to the next, and only the node with the token can transmit data • The device that receives the data from the token sends it back to the server along with an acknowledgment
- 22. • Only an endpoint with access to an ’empty’ token can transmit data at a given time, while the other computers have to wait for their turn ❑ Advantages ▪ Circular flow of data minimizes packet collision ▪ Unidirectional ring topologies feature high-speed data transmission ▪ Robust system–can handle a high number of nodes and heavy traffic ▪ Faults are located more easily, making troubleshooting efficient ❑ Disadvantages ▪ A single failure in the cable can disrupt overall network operations ▪ Unidirectional ring networks see data packets pass through numerous nodes before reaching their destination ▪ Adding, modifying, or removing nodes is difficult and can disrupt network activity TYPES OF NETWORK TOPOLOGY CONTD…
- 23. ❑ Star Topology ▪ All nodes are connected to a central hub using a communication link ▪ Each node needs a separate wire to establish a point-to-point connection with the hub, which functions as a server to control and manage the entire network ▪ If one endpoint wants to transmit data to another endpoint, it must send the request to the central hub, forwarding the message to the intended recipient TYPES OF NETWORK TOPOLOGY CONTD…
- 24. ❑ Advantages ▪ Easy network maintenance and management since each node has its own cable ▪ Failures affect only one device and problem areas are located swiftly ▪ Adding new devices is simple and straightforward ▪ Rapid data transfer ❑ Disadvantages ▪ Choosing the right central hub is vital, as this device needs to be compatible with all nodes and links in the network ▪ Higher requirement of cables and connectors ▪ Failure of the central hub brings down the entire network TYPES OF NETWORK TOPOLOGY CONTD…
- 25. ❑ Mesh topology ▪ In a mesh topology, all the nodes are interconnected and can send and receive their data and relay data from other nodes TYPES OF NETWORK TOPOLOGY CONTD… • Full mesh networks, wherein each node is connected to every other node, are usually reserved for critical networks as they are extremely costly to implement and challenging to maintain • IT teams also have the option of implementing partial mesh networks, wherein all the nodes are not connected • This is less cost-intensive and easier to implement; however, it does not have all the advantages of a full mesh network
- 26. ❑ Advantages • Extremely robust and redundant, as any node or link failure, affects a minimum number of endpoints • Highly efficient data transfer due to dedicated point-to-point links for all devices • Robust security and privacy ❑ Disadvantages • Requires many cables and input/output (I/O) ports • Time-consuming installation and maintenance • Cost-intensive s TYPES OF NETWORK TOPOLOGY CONTD…
- 27. ❑ Hybrid topology • A hybrid network topology, as the name suggests, features characteristics of multiple other topologies • The creation of such a configuration depends on the requirement of the network TYPES OF NETWORK TOPOLOGY CONTD…
- 28. • Two most commonly used hybrid topologies are star-ring and star-bus • In star-ring, the central hubs of multiple star topologies are linked using a ring topology • In star-bus the hubs of numerous star topologies are connected using a bus topology ❑ Advantages • Combines the advantages of multiple topologies • Can be tailor-made to suit specific network requirements • Highly flexible and scalable if implemented correctly ❑ Disadvantages • Depending on the configuration, such a network can be resource- intensive to create and maintain • Potentially complicated design that could make troubleshooting difficult • Requires compatible cabling and other hardware for inter-topology links TYPES OF NETWORK TOPOLOGY CONTD…
- 29. Dr. Sonali Chakraborty Email: chakrabartysonali@gmail.com 23