Computer networks - module-1 presentation

Computer networks

1. COMPUTER NETWORKS(BCS502) MODULE – 01 Data Communications & Networks Mrs. Vinutha K Assistant Professor, Dept. of CSE, SJBIT

2. Introduction DATA COMMUNICATIONS Components Data Representation Data Flow NETWORKS Network Criteria Physical Structures NETWORK TYPES Local Area Network Wide Area Network Switching The Internet Accessing the Internet

3. DATA COMMUNICATIONS Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. The process of transferring data from one point to another using a communication system. Involves essential components and mechanisms to ensure accurate and timely delivery of data .

4. Components of Data Communication System Message : The data/information being communicated (e.g., text, images, audio). Sender : Device that sends the message (e.g., computer, smartphone). Receiver : Device that receives the message (e.g., computer, printer). Transmission Medium : Physical path for data transmission (e.g., cables, radio waves). Protocol : Set of rules governing communication between devices for proper data exchange.

5. Components of Data Communication System Key performance Characteristics of Data Communication Delivery : Ensures data reaches the correct destination. Accuracy : Data must be transmitted without errors. Timeliness : Data should be delivered promptly, especially in real-time applications. Jitter : Refers to inconsistencies in packet arrival times, affecting quality (e.g., video streaming).

6. Components of Data Communication System Data Representation Different forms of representing data based on communication needs: Text : Represented as bits using encoding like ASCII, Unicode. Numbers : Directly in binary form. Images : Matrix of pixels, color coded (e.g., RGB, YCM). Audio : Captured as a continuous signal, digitized for transmission. Video : Sequence of frames, each frame represented as bit patterns.

7. Components of Data Communication System Data Flow Modes of data transmission between devices: Simplex : One-way communication (e.g., keyboard to computer). Half-Duplex : Two-way communication, but not simultaneous (e.g., walkie-talkie). Full-Duplex : Simultaneous two-way communication (e.g., phone conversation).

8. Data flow (simplex, half-duplex, and full-duplex)

9. NETWORKS A network is a set of devices (often referred to as nodes ) connected by communication links . A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

10. NETWORKS Interconnection of devices capable of communication. Devices : Hosts (e.g., computers, smartphones) and connecting devices (e.g., routers, switches). Transmission Media : Wired: Cables (Ethernet, fiber). Wireless: Air (Wi-Fi, cellular).

11. NETWORKS

12. NETWORKS Network Criteria 1. Performance : Transit time : Time for data to travel between devices. Response time : Time between a request and a response. Factors Affecting Performance : Number of users. Transmission medium. Hardware/software capabilities. Key Metrics : Throughput : Successful data transmission rate. Delay : Time for data to reach its destination.

13. NETWORKS Network Criteria 2. Reliability : Accuracy : Correct delivery of data. Failure Recovery : Speed of recovery from failures. Catastrophic Events : Ability to function in a disaster. 3. Security : Protects data from unauthorized access or damage. Involves security breach recovery procedures.

14. NETWORKS Physical Structures of Networks Types of Connection : Point-to-Point : Direct link between two devices (e.g., remote control to TV). Multipoint (Multidrop) : Shared link between multiple devices.

15. Types of connections: point-to-point and multipoint

16. Network Topologies Categories of topology

17. Network Topologies Mesh Topology : Every device is connected to every other device. Advantages : Dedicated links, robust, secure, good fault isolation. Disadvantages : Expensive, complex, lots of cabling. Example : Telephone networks. Star Topology : Devices connect to a central hub. Advantages : Easy to install, fault isolation. Disadvantages : Hub failure affects the whole system. Common Use : Local Area Networks (LANs).

18. A fully connected mesh topology (five devices)

19. A star topology connecting four stations

20. Network Topologies Bus Topology All devices share a single backbone cable. Advantages : Easy installation, less cabling. Disadvantages : Fault in the backbone affects the entire network. Example : Early Ethernet LANs.

21. A bus topology connecting three stations

22. Network Topologies Ring Topology Devices form a loop, data travels in one direction. Advantages : Easy fault detection, simple setup. Disadvantages : Break in the loop disables the network, mitigated by dual rings. Example : IBM Token Ring LANs.

23. A ring topology connecting six stations

24. A hybrid topology: a star backbone with three bus networks

25. An isolated LAN connecting 12 computers to a hub in a closet

26. Network Types Networks are often interconnected to form an internetwork, allowing seamless communication across different geographical areas and network types . Local Area Network (LAN) Wide Area Network (WAN)

27. Network Types Local Area Network (LAN) A LAN connects computers and devices within a small geographical area, such as a home, office, or campus. Characteristics: Covers a limited area. High data transfer rates (up to 10 Gbps). Owned and managed by a single organization. Examples: Ethernet networks Wi-Fi networks in homes/offices

28. Network Types Local Area Network (LAN)

29. Network Types Local Area Network (LAN) LAN Setup (Past): Common Cable Connection: All hosts connected via a single cable. Packet Transmission: Packets were broadcast to all hosts. Packet Filtering: Only the intended recipient accepted the packet. Drawback: Created network congestion due to excessive broadcasting.

30. Network Types Local Area Network (LAN) Switch-Based LAN : Smart switches manage packet delivery. Address Recognition: Switches identify the destination of each packet. Selective Packet Forwarding: Packets are sent directly to the recipient, reducing traffic. Simultaneous Communication: Multiple communications can occur simultaneously between different hosts. Benefits: Reduced network traffic and improved efficiency.

31. Network Types Wide Area Network (WAN) A WAN covers a large geographical area, connecting multiple LANs. Spans cities, countries, or globally. Characteristics: Slower data transfer rates than LANs. Managed by multiple entities (ISPs, governments). Utilizes routers and communication links (public/private). Examples: The Internet Private networks connecting company branches

32. Network Types Wide Area Network (WAN) A Point-to-Point WAN: Connects two devices directly via transmission media (cables or wireless links). Transmission Media: Fiber optic, coaxial, twisted-pair cables, or wireless links like microwaves and satellites. Advantages: Dedicated Line: Minimal congestion and consistent bandwidth. Security: Limited exposure reduces unauthorized access risks.

33. Network Types Wide Area Network (WAN) A Switched WAN: A network with multiple endpoints interconnected via switches. Allows dynamic routing between nodes. Role: Backbone of global communication systems (e.g., the Internet). Scalable and connects many endpoints. Switches select the best path for data transfer.

34. WANs: a switched WAN and a point-to-point WAN

35. Network Types Wide Area Network (WAN) Heterogeneous Network A system connecting various devices and network architectures (LANs and WANs). Heterogeneous: Involves diverse hardware, operating systems, and communication protocols. WANs act as the backbone for long-distance communication, while LANs enable local connectivity.

36. A heterogeneous network made of four WANs and two LANs

37. Switching Switching is the process of forwarding data packets in a network from a source to a destination through intermediate devices called switches .

38. Switching Types of Switching: 1. Circuit Switching: A fixed connection (circuit) is established between two devices for the duration of the communication, typically used in telephone networks. Key Features : A dedicated path is established before data transmission. The connection remains until the communication ends. Continuous and reserved bandwidth throughout the session.

39. Switching Types of Switching: 1. Circuit Switching:

40. Switching 1. Circuit Switching: Example (Figure 1.13) : Four telephones on each side are connected to a switch. The switch creates a connection between two phones on opposite sides. The main line between the switches has the capacity for four simultaneous voice calls. Scenario 1 : All phones are in use, using the full capacity of the line. Scenario 2 : One phone is in use, with only one-quarter of the capacity used. Disadvantages : Inefficiency when fewer devices are active. The thick line must have four times the capacity of a single voice line to handle all potential calls. Resources remain dedicated even when not in use.

41. Switching 2. Packet Switching: Data is divided into packets that are transmitted independently over the network. No dedicated path is established as in circuit switching. Key Features : Data is split into small packets, sent independently, and reassembled at the destination. Efficient use of network resources as bandwidth is shared dynamically. Packets may take different routes to reach the destination.

42. Switching 2. Packet Switching:

43. Switching 2 . Packet Switching: Example (Figure 1.14) : Two sets of four computers are connected across two sites through routers. Packets are queued and forwarded by the router when the network is ready. Scenario : The main connection has twice the capacity of the smaller lines. If only two computers are communicating, packets move without delay. If the connection is busy, packets are queued. Disadvantages : Can introduce delays when the network is congested. Requires more complex routing and addressing mechanisms compared to circuit switching.

44. THE INTERNET The Internet is a global system of interconnected computer networks using the TCP/IP protocol to link billions of devices worldwide. Characteristics : Decentralized : No central controlling entity. Based on TCP/IP : The foundation for communication across the Internet. Enables Various Services : Web browsing, email, file sharing, video streaming, etc. Components : Clients : Devices (computers, smartphones) requesting services from servers. Servers : Systems providing resources and services to clients. Routers & Switches : Devices that direct data traffic across the network. ISPs (Internet Service Providers) : Organizations providing Internet access to users.

45. THE INTERNET

46. THE INTERNET The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use.

47. THE INTERNET Accessing the Internet 1. Dial-up Uses a telephone line to connect to the Internet. Low-speed : Outdated, up to 56 kbps. 2. DSL (Digital Subscriber Line) Uses telephone lines but allows simultaneous voice and data transmission. Faster than Dial-up : Up to 100 Mbps.

48. THE INTERNET Accessing the Internet 3. Cable Uses cable television lines for Internet access. High-speed : Up to 1 Gbps. 4. Fiber Optic Uses light signals transmitted through optical fibers. Extremely high-speed : Up to 10 Gbps and beyond. 5. Satellite Internet via satellite communication, ideal for remote areas. Slower than fiber or cable, but wide coverage .

49. THE INTERNET 6. Mobile Broadband Wireless Internet access through cellular networks (3G, 4G, 5G). Widely accessible , but may have data limits . 7. Wi-Fi Access Wireless local area network technology that enables Internet access within the range of a wireless router. Common in homes, offices, and public places .

50. Continued….!! Module - 1