class 11 notes

Class 11 Computer and Communicatio Notes Chapter 2 (Chapter 2) – CCT Part-II Book

Philoid

Philoid

— 7 min read

CCT Part-II
Alright class, let's get straight into Chapter 2: Basics of Computer Networks. This is a fundamental chapter, and understanding these concepts well is crucial, not just for your exams but also for grasping how the digital world connects. Pay close attention, as questions from this area frequently appear in various government recruitment exams.

Chapter 2: Basics of Computer Networks - Detailed Notes

1. What is a Computer Network?

  • Definition: A computer network is a collection of two or more interconnected computers and other devices (like printers, scanners) that can communicate and share resources (data, hardware, software).
  • Purpose: The primary goal is to enable communication and resource sharing.
  • Advantages:
    • Resource Sharing: Hardware (printers, scanners), software (applications), and data can be shared among users, reducing cost and redundancy.
    • Communication: Enables fast and efficient communication through email, instant messaging, video conferencing, etc.
    • Reliability: Data can be backed up on multiple machines. If one machine fails, others can often take over its tasks (depending on the setup).
    • Cost Effectiveness: Sharing resources reduces the need to buy multiple pieces of hardware or software licenses.
    • Centralized Management: Data and resources can often be managed centrally, improving security and administration.

2. Essential Network Components

  • Nodes/Hosts: Any device connected to the network capable of sending, receiving, or forwarding information (e.g., computers, servers, printers, smartphones).
  • Server: A powerful computer that provides specific services or resources to other computers (clients) on the network (e.g., file server, print server, web server).
  • Client: A computer or device that requests services or resources from a server.
  • Network Interface Card (NIC): A hardware component, typically built into the motherboard or added as an expansion card, that allows a computer to connect to a network. Each NIC has a unique physical address called the MAC (Media Access Control) address.
  • Communication Media (Transmission Media): The physical path through which data travels between nodes.
    • Wired Media:
      • Twisted Pair Cable: Most common LAN cable (like Ethernet cables - Cat 5e, Cat 6). Consists of pairs of insulated copper wires twisted together to reduce interference. Relatively inexpensive.
      • Coaxial Cable: Contains a central copper conductor surrounded by insulation, a braided metal shield, and an outer jacket. Used for cable TV and older Ethernet networks. Offers better shielding than twisted pair.
      • Optical Fiber Cable: Transmits data as pulses of light through thin strands of glass or plastic. Offers very high bandwidth, long distances, and immunity to electromagnetic interference. More expensive and fragile.
    • Wireless Media:
      • Radio Waves: Used for Wi-Fi, Bluetooth, cellular networks. Can travel long distances and penetrate walls.
      • Microwaves: Used for point-to-point communication (satellite, microwave links). Require line-of-sight.
      • Infrared: Used for short-range communication (e.g., TV remotes, some older device connections). Requires line-of-sight and cannot penetrate walls.
  • Networking Devices:
    • Hub: A basic connecting device that repeats signals received on one port to all other ports. Operates at the Physical Layer. Creates a shared bandwidth environment (collision domain). Largely obsolete, replaced by switches.
    • Switch: A smarter device than a hub. It learns the MAC addresses of devices connected to its ports and forwards data only to the intended destination port. Operates at the Data Link Layer. Creates separate collision domains per port, improving efficiency.
    • Router: Connects different networks together (e.g., connects your home LAN to the Internet WAN). Makes decisions about the best path for data packets based on IP addresses. Operates at the Network Layer.
    • Modem (Modulator-Demodulator): Converts digital signals from a computer into analog signals suitable for transmission over telephone lines or cable systems, and vice versa. Needed for connecting to the internet via DSL or cable.
    • Gateway: A device that connects networks using different protocols. It acts as a translator between them. Often incorporated into routers.
    • Repeater: Amplifies or regenerates signals to enable them to travel longer distances over a communication medium. Operates at the Physical Layer.

3. Types of Networks (Based on Geographical Area)

  • PAN (Personal Area Network):
    • Covers a very small area, typically around a single person (few meters).
    • Connects personal devices like laptops, smartphones, headphones, keyboards.
    • Often uses wireless technologies like Bluetooth or wired like USB.
  • LAN (Local Area Network):
    • Covers a limited geographical area like a single building, office, school campus.
    • Typically privately owned.
    • High data transfer rates.
    • Common technologies: Ethernet (wired), Wi-Fi (wireless).
  • MAN (Metropolitan Area Network):
    • Covers a larger area than a LAN, such as a city or a large campus.
    • Can be a single network or interconnecting LANs.
    • May be owned by a single organization or a service provider.
    • Examples: Cable TV networks, city-wide Wi-Fi networks.
  • WAN (Wide Area Network):
    • Covers a large geographical area, often spanning countries or continents.
    • Connects multiple LANs or MANs.
    • Typically uses communication lines provided by public carriers (telephone companies, satellite operators).
    • The Internet is the largest example of a WAN.
    • Slower data transfer rates compared to LANs.

4. Network Topologies (Physical Layout)

  • Topology: Refers to the physical or logical arrangement of nodes and connections in a network.
  • Bus Topology:
    • All nodes are connected to a single central cable (the bus or backbone).
    • Terminators are used at both ends of the bus to absorb signals.
    • Advantages: Simple, inexpensive, easy to install for small networks.
    • Disadvantages: A break in the main cable disables the entire network. Performance degrades with heavy traffic. Difficult to troubleshoot.
  • Star Topology:
    • All nodes are connected to a central device (hub or switch).
    • Advantages: Easy to install and manage. Failure of one node or cable doesn't affect the rest of the network. Easy to detect faults.
    • Disadvantages: If the central device fails, the entire network fails. Requires more cabling than bus. Cost depends on the central device. (Most common topology for modern LANs).
  • Ring Topology:
    • Nodes are connected in a closed loop or ring. Data travels in one direction.
    • Each node receives data from the previous node and transmits it to the next.
    • Advantages: Performs well under heavy load (no collisions if using token passing).
    • Disadvantages: Failure of one node or cable can break the entire ring (unless using dual rings). Difficult to add/remove nodes.
  • Mesh Topology:
    • Every node is connected to every other node (Full Mesh) or at least multiple other nodes (Partial Mesh).
    • Advantages: Highly reliable and fault-tolerant (multiple paths exist). Excellent for high-traffic networks.
    • Disadvantages: Very expensive due to extensive cabling. Complex to install and manage. (Often used in WAN backbones).
  • Tree Topology (Hierarchical Topology):
    • A combination of bus and star topologies. Nodes are connected in a hierarchical structure.
    • Advantages: Scalable, easy to manage in segments. Fault identification is relatively easy.
    • Disadvantages: If the central hub/switch at a higher level fails, the segments below it are affected. More cabling required.

5. Network Architectures

  • Peer-to-Peer (P2P):
    • All computers have equal status (peers).
    • No dedicated server. Each computer can act as both a client and a server.
    • Users manage their own resources.
    • Advantages: Easy to set up, inexpensive.
    • Disadvantages: Not centralized (difficult administration), less secure, performance may degrade if many users access one peer simultaneously. Suitable for small networks (e.g., home networks).
  • Client-Server:
    • Uses dedicated servers to provide resources and services.
    • Clients request services from servers.
    • Advantages: Centralized management (security, backups, administration), scalable, more secure than P2P.
    • Disadvantages: Requires a dedicated server (costly), server failure can disrupt network services, requires network administrator. Suitable for most organizational networks.

6. Network Protocols

  • Protocol: A set of rules and conventions that govern communication between devices on a network. Ensures orderly and reliable data exchange.
  • TCP/IP (Transmission Control Protocol/Internet Protocol): The fundamental protocol suite of the Internet and most modern networks.
    • IP: Responsible for addressing and routing packets.
    • TCP: Provides reliable, connection-oriented data transmission (ensures data arrives correctly and in order).
  • Other Common Protocols:
    • HTTP (HyperText Transfer Protocol): Used for accessing and transferring files (especially web pages) on the World Wide Web.
    • HTTPS (HTTP Secure): Secure version of HTTP using encryption.
    • FTP (File Transfer Protocol): Used for transferring files between computers.
    • SMTP (Simple Mail Transfer Protocol): Used for sending email.
    • POP3 (Post Office Protocol version 3) / IMAP (Internet Message Access Protocol): Used for receiving email.
    • DNS (Domain Name System): Translates human-readable domain names (e.g., www.google.com) into IP addresses.

7. Internet and WWW

  • Internet: A global network of interconnected computer networks (WAN) that use the TCP/IP protocol suite. It's the infrastructure.
  • World Wide Web (WWW or Web): A system of interlinked hypertext documents accessed via the Internet. It's a service/application that runs on the Internet, using protocols like HTTP.

Multiple Choice Questions (MCQs)

  1. Which type of network covers the smallest geographical area, typically within a few meters around an individual?
    a) LAN
    b) WAN
    c) MAN
    d) PAN

  2. Which network device operates at the Data Link Layer and forwards data packets only to the intended recipient port based on MAC addresses?
    a) Hub
    b) Router
    c) Switch
    d) Repeater

  3. In which network topology does the failure of a central connecting device disable the entire network?
    a) Bus
    b) Ring
    c) Star
    d) Mesh

  4. Which communication medium uses pulses of light transmitted through thin strands of glass?
    a) Twisted Pair Cable
    b) Coaxial Cable
    c) Optical Fiber Cable
    d) Radio Waves

  5. What does the acronym TCP stand for in the context of network protocols?
    a) Transfer Control Protocol
    b) Transmission Control Protocol
    c) Transaction Control Protocol
    d) Transport Communication Protocol

  6. A network confined to a single building or a school campus is typically classified as a:
    a) PAN
    b) LAN
    c) MAN
    d) WAN

  7. Which network architecture features computers with equal status, where each can act as both a client and a server?
    a) Client-Server
    b) Hierarchical
    c) Peer-to-Peer
    d) Domain-based

  8. Which device is primarily responsible for connecting different networks together and routing traffic between them based on IP addresses?
    a) Switch
    b) Modem
    c) Hub
    d) Router

  9. Which protocol is fundamental for accessing web pages on the World Wide Web?
    a) FTP
    b) SMTP
    c) HTTP
    d) POP3

  10. What is the unique physical address assigned to every Network Interface Card (NIC)?
    a) IP Address
    b) Port Address
    c) MAC Address
    d) Subnet Mask

Make sure you revise these notes thoroughly. Understand the definitions, differences, advantages, and disadvantages of each concept. Good luck with your preparation!

Answers to MCQs:

  1. d) PAN
  2. c) Switch
  3. c) Star
  4. c) Optical Fiber Cable
  5. b) Transmission Control Protocol
  6. b) LAN
  7. c) Peer-to-Peer
  8. d) Router
  9. c) HTTP
  10. c) MAC Address

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