Chapter-1-Computer-Network-Introduction.pptx
- 1. Chapter 1 Computer Network Introduction
- 3. Computer Network ⮚ A set of communication elements connected by communication links. ⮚ Network, in computer science, a group of computers and associated devices that are connected by communications facilities. ⮚ Network is an inter connected collection of autonomous computers. ⮚ A computer network is a collection of computing devices that are connected with each other for the purpose of information and resource sharing among a wide variety of users. ⮚ A computer network is a system that connects two or more computing devices for transmitting and sharing information. Computing devices include everything from a mobile phone to a server. These devices are connected using physical wires such as fiber optics, but they can also be wireless. ⮚ Each device in the network is called a node which is connected to other nodes through wired or wireless media.
- 4. Why need computer network? ⮚ Better connectivity ⮚ Better communication ⮚ Better sharing of resources ⮚ Bring people together ⮚ Access remote data ⮚ Overcome geographic limits
- 6. Network Component Computer network components are the major parts which are needed to install the software. Hardware Components ⮚ Servers ⮚ Clients ⮚ Peers ⮚ Transmission Media ⮚ Connecting Devices ⮚ Routers, Bridges, Hubs, Repeaters, Gateways, Switches Software Components ⮚ Networking Operating System ⮚ Protocol Suite ⮚ a. OSI Model ( Open System Interconnections) ⮚ b. TCP / IP Model
- 7. Network Architecture ⮚ Network architecture refers to the way network devices and services are structured to serve the connectivity needs of client devices. ⮚ Network architecture is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as communication protocols used. There are two major types of network architectures: ⮚ Peer-To-Peer Architecture ⮚ Client/Server Architecture
- 8. Peer-To-Peer Network Architecture ⮚ Peer-To-Peer network is a network in which all the computers are linked together with equal privilege and responsibilities for processing the data. ⮚ Peer-To-Peer network is useful for small environments, usually up to 10 computers. ⮚ Peer-To-Peer network has no dedicated server. ⮚ Special permissions are assigned to each computer for sharing the resources, but this can lead to a problem if the computer with the resource is down. Advantages Of Peer-To-Peer Network: ⮚ It is less costly as it does not contain any dedicated server. ⮚ If one computer stops working but, other computers will not stop working. ⮚ It is easy to set up and maintain as each computer manages itself. Disadvantages Of Peer-To-Peer Network: ⮚ In the case of Peer-To-Peer network, it does not contain the centralized system . Therefore, it cannot back up the data as the data is different in different locations. ⮚ It has a security issue as the device is managed itself.
- 9. Client/Server Architecture ⮚ Client/Server network is a network model designed for the end users called clients, to access the resources such as songs, video, etc. from a central computer known as Server. ⮚ The central controller is known as a server while all other computers in the network are called clients. ⮚ A server performs all the major operations such as security and network management. ⮚ A server is responsible for managing all the resources such as files, directories, printer, etc. ⮚ All the clients communicate with each other through a server. For example, if client1 wants to send some data to client 2, then it first sends the request to the server for the permission. The server sends the response to the client 1 to initiate its communication with the client 2.
- 10. Advantages of Client/Server network: ⮚ A Client/Server network contains the centralized system. Therefore we can back up the data easily. ⮚ A Client/Server network has a dedicated server that improves the overall performance of the whole system. ⮚ Security is better in Client/Server network as a single server administers the shared resources. ⮚ It also increases the speed of the sharing resources. Disadvantages of Client/Server network: ⮚ Client/Server network is expensive as it requires the server with large memory. ⮚ A server has a Network Operating System(NOS) to provide the resources to the clients, but the cost of NOS is very high. ⮚ It requires a dedicated network administrator to manage all the resources.
- 11. Peer-To-Peer Architecture vs Client/Server Architecture S.N Client-Server Network Peer-to-Peer Network 1 In Client-Server Network, Clients and server are differentiated, Specific server and clients are present. In Peer-to-Peer Network, Clients and server are not differentiated. 2 Client-Server Network focuses on information sharing. While Peer-to-Peer Network focuses on connectivity. 3 In Client-Server Network, Centralized server is used to store the data. While in Peer-to-Peer Network, Each peer has its own data. 4 In Client-Server Network, Server respond the services which is request by Client. While in Peer-to-Peer Network, Each and every node can do both request and respond for the services. 5 Client-Server Network are costlier than Peer-to- Peer Network. While Peer-to-Peer Network are less costlier than Client- Server Network. 6 Client-Server Network are more stable than Peer- to-Peer Network. While Peer-to-Peer Network are less stable if number of peer is increase. 7 Client-Server Network is used for both small and large networks. While Peer-to-Peer Network is generally suited for small networks with fewer than 10 computers.
- 12. Network representation and topology Network topology refers to how various nodes, devices, and connections on your network are physically or logically arranged in relation to each other. Network Topology ⮚ Bus ⮚ Ring ⮚ Star ⮚ Mesh ⮚ Tree ⮚ Hybrid
- 13. Bus Topology
- 14. Bus Topology ⮚ The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable. ⮚ Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable. ⮚ 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. ⮚ The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks. ⮚ The configuration of a bus topology is quite simpler as compared to other topologies. ⮚ The backbone cable is considered as a "single lane" through which the message is broadcast to all the stations.
- 15. Advantages of Bus topology: ⮚ Low-cost cable ⮚ Moderate data speeds ⮚ Familiar technology ⮚ Limited failure Disadvantages of Bus topology: ⮚ Extensive cabling ⮚ Difficult troubleshooting ⮚ Signal interference ⮚ Reconfiguration difficult
- 16. Ring Topology
- 17. Ring Topology ⮚ Ring topology is like a bus topology, but with connected ends. ⮚ The node that receives the message from the previous computer will retransmit to the next node. ⮚ The data flows in one direction, i.e., it is unidirectional. ⮚ The data flows in a single loop continuously known as an endless loop. ⮚ It has no terminated ends, i.e., each node is connected to other node and having no termination point. ⮚ The data in a ring topology flow in a clockwise direction. ⮚ The most common access method of the ring topology is token passing.
- 18. Ring Topology ⮚ The most common access method of the ring topology is token passing. ⮚ Token passing: It is a network access method in which token is passed from one node to another node. ⮚ Token: It is a frame that circulates around the network. Working of Token passing ⮚ A token moves around the network, and it is passed from computer to computer until it reaches the destination. ⮚ The sender modifies the token by putting the address along with the data. ⮚ The data is passed from one device to another device until the destination address matches. Once the token received by the destination device, then it sends the acknowledgment to the sender. ⮚ In a ring topology, a token is used as a carrier.
- 19. Advantages of Ring topology: ⮚ Network Management ⮚ Product availability ⮚ Cost ⮚ Reliable Disadvantages of Ring topology: ⮚ Difficult troubleshooting Failure ⮚ Reconfiguration difficult ⮚ Delay
- 20. Star Topology
- 21. Star Topology ⮚ Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer. ⮚ The central computer is known as a server, and the peripheral devices attached to the server are known as clients. ⮚ Coaxial cable or RJ-45 cables are used to connect the computers. ⮚ Hubs or Switches are mainly used as connection devices in a physical star topology. ⮚ Star topology is the most popular topology in network implementation.
- 22. Advantages of Star topology ⮚ Efficient troubleshooting ⮚ Network control ⮚ Limited failure ⮚ Familiar technology ⮚ Easily expandable ⮚ Cost effective ⮚ High data speeds Disadvantages of Star topology ⮚ A Central point of failure ⮚ Cable
- 23. Mesh Topology
- 24. ⮚ Mesh technology is an arrangement of the network in which computers are interconnected with each other through various redundant connections. ⮚ There are multiple paths from one computer to another computer. ⮚ It does not contain the switch, hub or any central computer which acts as a central point of communication. ⮚ The Internet is an example of the mesh topology. ⮚ Mesh topology is mainly used for WAN implementations where communication failures are a critical concern. ⮚ Mesh topology is mainly used for wireless networks. Mesh topology is divided into two categories: ⮚ Fully connected mesh topology ⮚ Partially connected mesh topology
- 25. Advantages of Mesh topology: ⮚ Reliable ⮚ Fast Communication ⮚ Easier Reconfiguration Disadvantages of Mesh topology ⮚ Cost ⮚ Management ⮚ Efficiency
- 26. Hybrid Topology
- 27. ⮚ The combination of various different topologies is known as Hybrid topology. ⮚ A Hybrid topology is a connection between different links and nodes to transfer the data. ⮚ 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 Nabil bank and bus topology in another branch of Nabil bank, connecting these two topologies will result in Hybrid topology.
- 28. Advantages of Hybrid Topology ⮚ Reliable ⮚ Scalable ⮚ Flexible ⮚ Effective Disadvantages of Hybrid topology ⮚ Complex design ⮚ Costly Hub ⮚ Costly infrastructure
- 30. Transmission modes ⮚ The way in which data is transmitted from one device to another device is known as transmission mode. ⮚ The transmission mode is also known as the communication mode. ⮚ Each communication channel has a direction associated with it, and transmission media provide the direction. Therefore, the transmission mode is also known as a directional mode.
- 32. Simplex mode
- 33. ⮚ In Simplex mode, the communication is unidirectional, i.e., the data flow in one direction. ⮚ A device can only send the data but cannot receive it or it can receive the data but cannot send the data. ⮚ This transmission mode is not very popular as mainly communications require the two- way exchange of data. The simplex mode is used in the business field as in sales that do not require any corresponding reply. ⮚ The radio station is a simplex channel as it transmits the signal to the listeners but never allows them to transmit back. ⮚ The main advantage of the simplex mode is that the full capacity of the communication channel can be utilized during transmission. Advantage of Simplex mode: ⮚ In simplex mode, the station can utilize the entire bandwidth of the communication channel, so that more data can be transmitted at a time. Disadvantage of Simplex mode: ⮚ Communication is unidirectional, so it has no inter-communication between devices.
- 34. Half-Duplex mode
- 35. ⮚ In a Half-duplex channel, direction can be reversed, i.e., the station can transmit and receive the data as well. ⮚ Messages flow in both the directions, but not at the same time. ⮚ The entire bandwidth of the communication channel is utilized in one direction at a time. ⮚ In half-duplex mode, it is possible to perform the error detection, and if any error occurs, then the receiver requests the sender to retransmit the data. ⮚ A Walkie-talkie is an example of the Half-duplex mode. In Walkie-talkie, one party speaks, and another party listens. After a pause, the other speaks and first party listens. Speaking simultaneously will create the distorted sound which cannot be understood. Advantage of Half-duplex mode: ⮚ In half-duplex mode, both the devices can send and receive the data and also can utilize the entire bandwidth of the communication channel during the transmission of data. Disadvantage of Half-Duplex mode: ⮚ In half-duplex mode, when one device is sending the data, then another has to wait, this causes the delay in sending the data at the right time.
- 36. Duplex Mode
- 37. ⮚ In Full duplex mode, the communication is bi-directional, i.e., the data flow in both the directions. ⮚ Both the stations can send and receive the message simultaneously. ⮚ Full-duplex mode has two simplex channels. One channel has traffic moving in one direction, and another channel has traffic flowing in the opposite direction. ⮚ The Full-duplex mode is the fastest mode of communication between devices. ⮚ The most common example of the full-duplex mode is a telephone network. When two people are communicating with each other by a telephone line, both can talk and listen at the same time. Advantage of Full-duplex mode: ⮚ Both the stations can send and receive the data at the same time. Disadvantage of Full-duplex mode: ⮚ If there is no dedicated path exists between the devices, then the capacity of the communication channel is divided into two parts.
- 38. Differences b/w Simplex, Half-duplex and Full-duplex mode Basis for comparison Simplex mode Half-duplex mode Full-duplex mode Direction of communication In simplex mode, the communication is unidirectional. In half-duplex mode, the communication is bidirectional, but one at a time. In full-duplex mode, the communication is bidirectional. Send/Receive A device can only send the data but cannot receive it or it can only receive the data but cannot send it. Both the devices can send and receive the data, but one at a time. Both the devices can send and receive the data simultaneously. Performance The performance of half-duplex mode is better than the simplex mode. The performance of full- duplex mode is better than the half-duplex mode. The Full-duplex mode has better performance among simplex and half-duplex mode as it doubles the utilization of the capacity of the communication channel. Example Examples of Simplex mode are radio, keyboard, and monitor. Example of half-duplex is Walkie-Talkies. Example of the Full-duplex mode is a telephone network.
- 39. Network type ⮚ Personal Area Network (PAN) ⮚ Local Area Network (LAN) ⮚ Wireless Local Area Network (WLAN) ⮚ Metropolitan Area Network (MAN) ⮚ Wide Area Network (WAN) ⮚ Virtual Private Network (VPN)
- 40. LAN (Local Area Network) ⮚ Local Area Network is a group of computers connected to each other in a small area such as building, office. ⮚ LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. ⮚ It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables. ⮚ The data is transferred at an extremely faster rate in Local Area Network. ⮚ Local Area Network provides higher security.
- 41. PAN (Personal Area Network) ⮚ Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters. ⮚ Personal Area Network is used for connecting the computer devices of personal use is known as Personal Area Network. ⮚ Thomas Zimmerman was the first research scientist to bring the idea of the Personal Area Network. ⮚ Personal Area Network covers an area of 30 feet. ⮚ 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: ⮚ Wired Personal Area Network ⮚ Wireless Personal Area Network
- 42. MAN (Metropolitan Area Network) ⮚ A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. ⮚ Government agencies use MAN to connect to the citizens and private industries. ⮚ In MAN, various LANs are connected to each other through a telephone exchange line. ⮚ The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc. ⮚ It has a higher range than Local Area Network (LAN). Uses of Metropolitan Area Network: ⮚ MAN is used in communication between the banks in a city. ⮚ It can be used in an Airline Reservation. ⮚ It can be used in a college within a city. ⮚ It can also be used for communication in the military.
- 43. WAN (Wide Area Network) ⮚ A Wide Area Network is a network that extends over a large geographical area such as states or countries. ⮚ A Wide Area Network is quite bigger network than the LAN. ⮚ 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. ⮚ The internet is one of the biggest WAN in the world. ⮚ A Wide Area Network is widely used in the field of Business, government, and education.
- 44. Difference Between LAN, MAN and WAN
- 46. Protocol ⮚ The word protocol comes from the Greek protocollon, meaning a leaf of paper glued to a manuscript volume that describes the contents. ⮚ A protocol is a set of rules that govern how systems communicate. For networking they govern how data is transferred from one system to another. ⮚ Network Protocols are a set of rules governing exchange of information in an easy, reliable and secure way. ⮚ Network protocols conduct the policy of end-to-end processes of timely, secure and managed data or network communication. ⮚ A network protocol includes the pre-defined rules and conventions for communication between network and devices connected. These include identifying and establishing connections among devices. Besides, there are formatting rules specifying packaging, sending, and receiving messages. Additionally, there are protocols for message acknowledgment and data compression too. It also enables the establishment of reliable and high-performing network communication. ⮚ Network protocols are the reason you can easily communicate with people all over the world, and thus play a critical role in modern digital communications.
- 47. History of Protocols ⮚ The Internet base protocols and systems were mainly devised in the 1970s and 1980s. ⮚ TCP/IP describes a protocol which will work on any sort of computer and operating system for transportation of data across the internet between different systems ⮚ TCP/IP has proven to be remarkably robust, but is very basic.
- 48. Requirements of network protocol ⮚ Data formats for data exchange ⮚ Flow control ⮚ Routing ⮚ Acknowledgements ⮚ Loss of information ⮚ Sequence control
- 49. Elements of protocol ⮚ Message encoding ⮚ Message formatting and encapsulation ⮚ Message timing ⮚ Message size ⮚ Message delivery options
- 50. Message encoding: A source message from sender is encoded into signals or waves then transmitted through a medium wired / wireless then received and decoded and message is passed to destination. Encoding is the process of transforming set of Unicode characters into a sequence of bytes. Message Source –> Encoder –> Transmitter –> Transmitter Medium –>Receiver –>Decoder –> Message destination Message formatting and encapsulation: ⮚ There is an agreed format by sender and receiver. It encapsulates information to identify sender and receiver rightly. ⮚ A message format will depend on the type of message and the medium through which the message is delivered. ⮚ Message encapsulation is a process that is used to place one message inside another message for transfer from the source to the destination. Message Timing: It manages flow control. Acknowledgments response time out. This requires certain timing control information. It checks for any delays in data passing. It includes rules like Access method, flow control, response timeout.
- 51. Message size: ⮚ Here long messages must break into small pieces to travel across a network or the process of breaking up a long message into individual pieces before being sent over the network. ⮚ Example – In mobile phone SMS limits message size to 160 normal alphabet characters. For non- alphabet character, it needs 16 bit of data to represent them limiting size to 70 characters only. Message delivery options: ⮚ There are different delivery options like Unicast, Multicast, and Broadcast. ⮚ Sending information to a single person is referred to as a one-to-one delivery and is called unicast which implies that there is only one destination (single destination). ⮚ To communicate information to more than one person (Group of people at the same time) is referred to as one-to-many and is called multicast which implies that one sender to multiple destinations/recipients for the same message. ⮚ Sometimes information is to be communicated to every person in the same area. This is referred to as one-to-all and is called broadcast which implies that one sender sends a message to all connected recipients.
- 52. Protocol Suite ⮚ A protocol suite is a collection of protocols that are designed to work together. ⮚ The Internet protocol suite is the conceptual model and set of communications protocols used in the Internet and similar computer networks. It is commonly known as TCP/IP because the foundational protocols in the suite are the Transmission Control Protocol (TCP) and the Internet Protocol (IP). ⮚ The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed, and received. ⮚ This functionality is organized into four abstraction layers, which classify all related protocols according to the scope of networking involved. From lowest to highest, the layers are: ⮚ The link layer, containing communication methods for data that remains within a single network segment (link). ⮚ The internet layer, providing internetworking between independent networks. ⮚ The transport layer, handling host-to-host communication. ⮚ The application layer, providing process-to-process data exchange for applications.
- 53. Types of Network Protocols ⮚ Transmission Control Protocol (TCP). ⮚ Internet Protocol (IP) ⮚ Post office Protocol (POP) ⮚ User Datagram Protocol (UDP) ⮚ Simple mail transport Protocol (SMTP) ⮚ File Transfer Protocol (FTP) ⮚ Telnet ⮚ Hyper-Text Transfer Protocol (HTTP) ⮚ Hyper-Text Transfer Protocol Secure (HTTPS) ⮚ Gopher
- 54. Rules or protocols govern all methods of communication. All communication schemes will have the following things in common: ⮚ Source or sender ⮚ Destination or receiver ⮚ Channel or media
- 55. Network Standards ⮚ Networking standards define the rules for data communications that are needed for interoperability of networking technologies and processes. ⮚ Standards help in creating and maintaining open markets and allow different vendors to compete on the basis of the quality of their products while being compatible with existing market products. ⮚ During data communication, a number of standards may be used simultaneously at the different layers. The commonly used standards at each layer are − ⮚ Application layer − HTTP, HTML, POP, H.323, IMAP ⮚ Transport layer − TCP, SPX ⮚ Network layer −IP, IPX ⮚ Data link layer − Ethernet IEEE 802.3, X.25, Frame Relay ⮚ Physical layer −RS-232C (cable), V.92 (modem)
- 56. Types of Standards Standards are of two types ⮚ De facto: These are the standards that are followed without any formal plan or approval by any organization. They have come into existence due to traditions or facts. For example, the HTTP had started as a de facto standard. ⮚ De jure: These standards are the ones which have been adopted through legislation by any officially recognized standards organization. Most of the communication standards that are used today are de jure standards.
- 57. Standards Organizations Some of the noted standards organizations are ⮚ International Standards Organization (ISO) ⮚ International Telecommunication Union (ITU) ⮚ Institute of Electronics and Electrical Engineers (IEEE) ⮚ American National Standards Institute (ANSI) ⮚ Internet Research Task Force (IETF) ⮚ Internet Engineering Task Force (IETF) ⮚ Electronic Industries Association (EIA)
- 58. International Standards Organization (ISO) ⮚ ISO stands for International Organization for Standardization, is a nongovernmental organization based in Geneva, Switzerland, that has representatives from about 130 countries and is responsible for developing a variety of international standards in science and engineering. ⮚ The International Organization for Standardization (ISO), established in 1947, runs almost 3000 different working groups and committees covering a broad range of standards issues. ⮚ The ISO’s goals are to develop cooperation in scientific, technological, intellectual, and economic activities and to facilitate the international exchange of goods and services. ⮚ ISO has published 24000 plus International Standards and related documents, covering almost every industry, from technology, to food safety, to agriculture and healthcare. ISO International Standards impact everyone, everywhere.
- 59. ISO standards include the following: ⮚ Open Systems Interconnection (OSI) reference model for networking ⮚ ISO/IEC SQL-92 standard for the transact-SQL language ⮚ ISO codes for photographic film speeds ⮚ ISO 9000 framework for business-management and quality-assurance standards ⮚ ISO 216 international standard paper sizes ⮚ Standards for telephone and bank cards ⮚ ISO international country codes and currency codes
- 60. International Telecommunication Union (ITU) The International Telecommunication Union (ITU) is a United Nations specialised agency for information and communication technologies (ICTs). ⮚ In general terms, the Union focuses on three main areas of activity: ⮚ Radio communications (allocation of global radio spectrum and satellite orbits), through the ITU Radio communication Sector (ITU-R); ⮚ Standardisation (development of technical standards for the interconnection of networks and technologies), through the ITU Telecommunication Standardization Sector (ITU-T); ⮚ Development (working, among others, on improving access to ICTs to underserved communities worldwide), through the ITU Telecommunication Development Sector (ITU-D). ⮚ Some of ITU’s key areas of action include: telecommunications networks (including next generation networks and future networks), access and digital divide, accessibility to ICTs, ICTs and climate change, cybersecurity, child protection online, and gender equality. These topics are covered both within the framework of standardisation work, as well as in the context of various projects, initiatives, and studies carried out by the organisation.
- 61. Institute of Electronics and Electrical Engineers (IEEE) ⮚ The Institute of Electrical and Electronic Engineers (IEEE) is a global association and organization of professionals working toward the development, implementation and maintenance of technology- centered products and services. ⮚ IEEE is a non-profit organization founded in 1963. It works solely toward innovating, educating and standardizing the electrical and electronic development industry. It is best known for its development of standards such as IEEE 802.11. ⮚ IEEE primarily innovates new electronic products and services, designs the standards that govern them and imparts, publishes and promotes industry knowledge through publications, conferences and partnering with academic institutes. ⮚ The prime areas of focus for IEEE are electrical, electronics, computer engineering, computer science, information technology and most of their related disciplines. ⮚ IEEE develops many different standards, such as IEEE 802 and IEEE 802.11 (commonly known as Wi-Fi), and provides ongoing innovation, amendments and maintenance services for these standards. ⮚ IEEE also maintains thousands of student and professional chapters globally, has numerous focus societies and sponsors regular conferences and seminars. While the organization is US-based, its standards often become internationally accepted.
- 62. American National Standards Institute (ANSI) ⮚ ANSI Stands for "American National Standards Institute." ANSI is a U.S.-based non-profit organization that works to develop and promote standards in the United States and around the world. ⮚ ANSI was originally called the "American Engineering Standards Committee" (AESC), which was formed in 1918. The AESC worked with the American Institute of Electrical Engineers (now the IEEE) and several other organizations to develop engineering standards. In 1928, AESC was reorganized and renamed the "American Standards Association" (ASA). ⮚ The ASA began to develop partnerships with global organizations, such as the ISO and helped promote U.S. standards internationally. In 1969, the ASA was renamed to ANSI. ⮚ By standardizing new technologies, ANSI helps both corporations and government agencies create compatible products and services. For example, when ANSI standardizes a specific type of hardware port, computer manufacturers can build machines with the standardized port and know it will be compatible with third-party devices. When ANSI standardizes a file format, software developers can support the format in their programs, since information about the format is publicly available.
- 63. Internet Research Task Force (IRTF) ⮚ The Internet Research Task Force (IRTF) promotes research of importance to the evolution of the Internet by creating focused, long-term Research Groups working on topics related to Internet protocols, applications, architecture and technology. ⮚ The Internet Research Task Force (IRTF) focuses on longer term research issues related to the Internet while the parallel organization, the Internet Engineering Task Force (IETF), focuses on the shorter term issues of engineering and standards making. ⮚ The IRTF is a composed of a number of focused and long-term Research Groups. These groups work on topics related to Internet protocols, applications, architecture and technology. Research Groups have the stable long term membership needed to promote the development of research collaboration and teamwork in exploring research issues. Participation is by individual contributors, rather than by representatives of organizations. ⮚ The IRTF is managed by the IRTF Chair in consultation with the Internet Research Steering Group (IRSG). The IRSG membership includes the IRTF Chair, the chairs of the various Research Groups and other individuals (“members at large”) from the research community selected by the IRTF Chair.
- 64. Internet Engineering Task Force (IETF) ⮚ The Internet Engineering Task Force is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite. ⮚ The common areas of focus for the IETF include: General infrastructure, internet, operations and management of real-time applications, routing, security and transport. Electronic Industries Association (EIA) ⮚ The Electronic Industries Alliance (EIA; until 1997 Electronic Industries Association) was an American standards and trade organization composed as an alliance of trade associations for electronics manufacturers in the United States. ⮚ They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable. ⮚ The EIA ceased operations on February 11, 2011, but the former sectors continue to serve the constituencies of EIA. ⮚ Electronic industries alliance (EIA) which is an industry trade group of electronics and networking manufacturers that collaborates on standards for wiring, connectors, and other common components.
- 65. Standard organization of Nepal ⮚ Ministry of Communication and Information Technology ⮚ Department of Information ⮚ Nepal Telecommunications Authority (NTA) ⮚ Radio Broadcasting Development Committee
- 66. Reference models ⮚ Reference model; in systems, enterprise, and software engineering: is an abstract framework or domain-specific ontology consisting of an interlinked set of clearly defined concepts produced by an expert or body of experts to encourage clear communication. ⮚ A reference model can represent the component parts of any consistent idea, from business functions to system components, as long as it represents a complete set. This frame of reference can then be used to communicate ideas clearly among members of the same community. ⮚ Reference models are often illustrated as a set of concepts with some indication of the relationships between the concepts. ⮚ In computer networks, reference models give a conceptual framework that standardizes communication between heterogeneous networks. The two popular reference models are: ⮚ OSI Model ⮚ TCP/IP Protocol Suite
- 67. OSI Model ⮚ OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer. ⮚ OSI gives a layered networking framework that conceptualizes how communication should be done between heterogeneous systems. ⮚ OSI model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered as an architectural model for the inter-computer communications. ⮚ OSI consists of seven layers, and each layer performs a particular network function. The seven layers of the OSI Model are a physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. ⮚ OSI model divides the whole task into seven smaller and manageable tasks. Each layer is assigned a particular task. Each layer is self-contained, so that task assigned to each layer can be performed independently.
- 68. OSI Model Layers
- 69. The physical layer, data link layer and the network layer are the network support layers. The layers manage a physical transfer of data from one device to another. Session layer, presentation layer, and application layer are the user support layers. These layers allow communication among unrelated software in dissimilar environments. Transport layer links the two groups. The main functions of each of the layers are as follows − ⮚ Physical Layer − Its function is to transmit individual bits from one node to another over a physical medium. ⮚ Data Link Layer − It is responsible for the reliable transfer of data frames from one node to another connected by the physical layer. ⮚ Network Layer − It manages the delivery of individual data packets from source to destination through appropriate addressing and routing. ⮚ Transport Layer −It is responsible for delivery of the entire message from the source host to destination host. ⮚ Session Layer − It establishes sessions between users and offers services like dialog control and synchronization. ⮚ Presentation Layer − It monitors syntax and semantics of transmitted information through translation, compression, and encryption. ⮚ Application Layer − The application layer facilitates communication between software applications and the network, handling end-user interactions and enabling data exchange.
- 70. TCP / IP PROTOCOL Reference Model ⮚ TCP stands for Transmission Control Protocol, while IP stands for Internet Protocol. It is a suite of protocols for communication structured in five layers. ⮚ The TCP/IP model was developed prior to the OSI model. ⮚ The TCP/IP model is not exactly similar to the OSI model. ⮚ It can be used for communication over the internet as well as for private networks. ⮚ It was developed by the DoD (Department of Defence) in the 1960s. It is named after the two main protocols that are used in the model, namely, TCP and IP. ⮚ The TCP/IP model consists of five layers: the application layer, transport layer, network layer, data link layer and physical layer. ⮚ The first four layers provide physical standards, network interface, internetworking, and transport functions that correspond to the first four layers of the OSI model and these four layers are represented in TCP/IP model by a single layer called the application layer. ⮚ TCP/IP is a hierarchical protocol made up of interactive modules, and each of them provides specific functionality.
- 71. TCP / IP Protocol Layers
- 72. Difference between OSI model and TCP/IP model
- 73. Difference between OSI model and TCP/IP model
- 74. Data Encapsulation ⮚ Data Encapsulation is the process in which some extra information is added to the data item to add some features to it. ⮚ We use either the OSI or the TCP/IP model in our network, and the data transmission takes place through various layers in these models. ⮚ Data encapsulation adds the protocol information to the data so that data transmission can take place in a proper way. ⮚ This information can either be added in the header or the footer of the data. ⮚ The data is encapsulated on the sender’s side, starting from the application layer to the physical layer. ⮚ Each layer takes the encapsulated data from the previous layer and adds some more information to encapsulate it and some more functionalities with the data. ⮚ These functionalities may include proper data sequencing, error detection and control, flow control, congestion control, routing information, etc.
- 75. Encapsulation Process (At sender’s side) ⮚ Step 1: The Application, Presentation, and Session layer in the OSI model, or the Application layer in the TCP/IP model takes the user data in the form of data streams, encapsulates it and forwards the data to the Transport layer. It does not necessarily add any header or footer to the data. But it is application-specific and can add the header if needed. ⮚ Step 2: The Transport layer (in the OSI or TCP/IP model) takes the data stream from the upper layers, and divide it into multiple pieces. The Transport layer encapsulates the data by adding the appropriate header to each piece. These data pieces are now called as data segments. The header contains the sequencing information so that the data segments can be reassembled at the receiver’s end. ⮚ Step 3: The Network layer (in the OSI model) or the Internet layer (in the TCP/IP model) takes the data segments from the Transport layer and encapsulate it by adding an additional header to the data segment. This data header contains all the routing information for the proper delivery of the data. Here, the encapsulated data is termed as a data packet or datagram.
- 76. ⮚ Step 4: The Data-Link layer (in the OSI or TCP/IP model) takes the data packet or datagram from the Network layer and encapsulate it by adding an additional header and footer to the data packet or datagram. The header contains all the switching information for the proper delivery of the data to the appropriate hardware components, and the trailer contains all the information related to error detection and control. Here, the encapsulated data is termed as a data frame. ⮚ Step 5: The Physical layer (in the OSI or TCP/IP model) takes the data frames from the Data-Link layer and encapsulate it by converting it to appropriate data signals or bits (corresponding to the physical medium). Data De-encapsulation ⮚ Data De-encapsulation is the reverse process of data encapsulation. The encapsulated information is removed from the received data to obtain the original data. This process takes place at the receiver’s end. The data is de-encapsulated at the same layer at the receiver’s end to the encapsulated layer at the sender’s end. The added header and trailer information are removed from the data in this process.
- 77. De-Encapsulation Process (At receiver’s side) ⮚ Step 1: The Physical layer (in the OSI or TCP/IP model) takes the encapsulated data signals or bits from the sender, and de-encapsulate it in the form of a data frame to be forwarded to the upper layer, i.e., the Data- Link layer. ⮚ Step 2: The Data-Link layer (in the OSI or TCP/IP model) takes the data frames from the Physical layer. It de-encapsulates the data frames and checks the frame header whether the data frame is switched to the correct hardware or not. If the frame is switched to the incorrect destination, it is discarded, else it checks the trailer information. If there is any error in the data, data retransmission is requested, else it is de- encapsulated and the data packet is forwarded to the upper layer. ⮚ Step 3: The Network layer (in the OSI model) or the Internet layer (in the TCP/IP model) takes the data packet or datagram from the Data-Link layer. It de-encapsulates the data packets and checks the packet header whether the packet is routed to the correct destination or not. If the packet is routed to the incorrect destination, the packet is discarded, else it is de-encapsulated and the data segment is forwarded to the upper layer. ⮚ Step 4: The Transport layer (in the OSI or TCP/IP model) takes the data segments from the network layer and de-encapsulate it. It first checks the segment header and then reassembles the data segments to form data streams, and these data streams are then forwarded to the upper layers. ⮚ Step 5: The Application, Presentation, and Session layer in the OSI model, or the Application layer in the TCP/IP model takes encapsulated data from the Transport layer, de-encapsulate it, and the application- specific data is forwarded to the applications.
- 78. Data Encapsulation and De-encapsulation process
- 79. Network Devices used in each layer of TCP/IP model Network Devices: Network devices, also known as networking hardware, are physical devices that allow hardware on a computer network to communicate and interact with one another. For example Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC, RJ45 Connector, Modem etc. Physical Layer ⮚ Hubs ⮚ Cables ⮚ Repeaters Data Link Layer ⮚ Switch ⮚ Bridges ⮚ Modem ⮚ Network Interface Card Network Layer ⮚ Routers ⮚ Brouters Transport Layer ⮚ Gateways ⮚ Firewall Application Layer ⮚ PC’s (Personal Computer), Phones, Servers ⮚ Gateways and Firewalls
- 80. Network Devices used in each layer of TCP/IP model ⮚ Hubs: Hubs are devices commonly used to connect segments of a LAN. It contains multiple input/output ports. when signal is at any input port, this signal will be made at all output ports except the one it is coming from. ⮚ Cables: In Wired network architecture (e.g Ethernet), cables are used to interconnect the devices. some of the types of cables are coaxial cable, optical fiber cable, and twisted pair cable. ⮚ Repeaters: Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters can only amplify the signal whereas a digital repeaters can reproduce a signal to near its original quality. ⮚ Bridges: A bridge is a type of computer network device that provides interconnection with other networks that use the same protocol, connecting two different networks together and providing communication between them. ⮚ Switch: A switch is a multiport bridge with a buffer and a design that can boost its efficiency and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, which makes it very efficient as it does not forward packets that have errors and forward good packets selectively to the correct port only. ⮚ Modem: Modem stands for Modulator/Demodulator. A modem converts digital signals generated by the computer into analog signals which, then can be transmitted over cable line and transforms incoming analog signals into digital equivalents.
- 81. ⮚ Network Interface Card: Network interface card is an electronic device that is mounted on ROM of the com that connects a computer to a computer network, usually a LAN. It is considered a piece of computer hardware. Most modern computers support an internal network interface controller embedded in the motherboard directly rather than provided as an external component. ⮚ Routers: A router is a switch like device that routes/forwards data packets based on their IP addresses. Routers normally connect Local Area Network (LANs) and Wide Are Network (WANs) together and have a dynamically updating routing table based on which they make decisions on routing the incoming packets. ⮚ Brouters: A bridge router or brouter is a network device that works as a bridge and as a router. The brouter routes packets for known protocols and simply forwards all other packets as a bridge would. Brouters operate at both the network layer for routable protocols (or between network with different data link layer protocol ex. one is running on ethernet (802.3) and other network is running on Token ring (802.5)) and at the data link layer for non-routable protocols (or both network are using same data link layer protocol). ⮚ Gateways: In computer networking, a gateway is a component that is part of two networks, which use different protocols. The gateway is a protocol converter which will translate one protocol into the other. A router is a special case of a gateway. ⮚ Firewall: A firewall is a system designed to prevent unauthorized access to or from a private network, some of the functionalities of firewall are, packet filtering and as a proxy server.
- 82. Difference Between Hub, Switch and Router Hub Switch Router HUB work on Physical Layer of OSI Model Switch work on Data Link Layer of OSI Model Router work on Network Layer of OSI Model HUB is Broadcast Device Switch is Multicast Device Router is a routing device use to create route for transmitting data packets Hus is use to connect device in the same network Switch is use to connect devices in the same network Router is use to connect two or more different network. Hub sends data in the form of binary bits Switch sends data in the form of frames Router sends data in the form packets Hub only works in half duplex Switch works in full duplex Router works in full duplex Only one device can send data at a time Multiple devices can send data at the same time Multiple devices can send data at the same time Hub does not store any mac address or IP address Switch store MAC Address Router stores IP address