Computer Networks
1. What is a Computer Network?
• A computer network consists of two or more connected computers that communicate with each other.
• Major Components:
o Client and Server Computers: Clients request services, and servers provide them.
o Network Interfaces (NICs): Hardware that connects computers to the network.
o Connection Medium: Cables or wireless signals that transmit data.
o Network Operating System (NOS): Software that manages network resources.
o Hubs, Switches, and Routers: Devices that connect and direct data traffic.
o Software Defined Networks (SDN): Networks managed by software for greater flexibility.
2. Modern Corporate Networks
• Local Area Networks (LANs): Small networks within a building or campus.
• Servers: Powerful computers that provide services like hosting websites, intranets, and extranets.
• Mobile Wireless LANs (Wi-Fi): Wireless networks for mobile devices.
• Videoconferencing and Telephone Networks: Systems for communication.
3. Key Terms
• Bandwidth: The capacity of a communication channel, measured by the range of frequencies it can transmit.
• Broadband: High-speed transmission technology that can transmit multiple data channels simultaneously.
4. Protocols and Latency
• Protocol: A set of rules governing how data is transmitted over a network.
• Latency: The time it takes for data to travel from one point to another.
5. Metcalfe's Law
• The value of a network is proportional to the square of the number of connected users (N²). For example, a
network with 10 nodes has a value of 100.
6. Types of Networks
• LANs: Local networks within a small area.
• WANs: Wide Area Networks that cover large geographical areas.
• MANs: Metropolitan Area Networks that cover a city.
• CANs: Campus Area Networks that cover a university or business campus.
• Internet: The largest network, connecting millions of devices globally.
7. Client/Server Computing
• A distributed computing model where clients (user devices) are linked through a network controlled by a
server.
• The server manages communication rules and assigns addresses to clients.
8. Key Technologies: OSI and TCP/IP Models
• OSI Model: A conceptual framework for understanding network interactions in seven layers.
• TCP/IP Model: A simpler model with four layers (Application, Transport, Internet, Network Interface) that
governs data transmission over the internet.
9. Internet Addressing and Architecture
• IP Address: A unique 32-bit number assigned to each device on the internet (e.g., 207.46.250.119).
• DNS (Domain Name System): Converts IP addresses to human-readable domain names
(e.g., www.example.com).
10. Internet Services and Communication Tools
• Email, Chatting, Newsgroups, FTP, Telnet: Various services for communication and file transfer.
• World Wide Web: A service for accessing and sharing hypertext documents via web browsers.
• VoIP (Voice over IP): Digital voice communication using internet protocols.
• VPN (Virtual Private Network): A secure, encrypted network over the internet for private communication.
11. Searching the Web
• Search Engines: Tools like Google that index web pages and allow users to search for information.
• SEO (Search Engine Optimization): Techniques to improve a website's visibility in search results.
12. Sharing Information on the Web
• Blogs, RSS, Wikis, Social Networking: Platforms for sharing and collaborating on information.
13. Internet Architecture and Governance
• Network Service Providers: Companies that own and operate the internet's backbone infrastructure.
• Organizations: Bodies like IAB, ICANN, and W3C that establish internet standards and governance.
14. Transmission Media
• Wired: Twisted pair wires, coaxial cables, fiber optics.
• Wireless: Satellites, cellular systems.
• Transmission Speed: Measured in bits per second (bps), hertz, and bandwidth.
15. Wireless Networks
• Bluetooth: Short-range wireless communication for personal area networks (PANs).
• Wi-Fi: Standards for wireless LANs and internet access, using access points and hotspots.
• WiMax: An older standard for wireless broadband (now considered obsolete).
16. Future of the Web
• Internet of Things (IoT): Connecting everyday devices to the internet.
• Cloud Computing: Increased use of cloud-based services and software (SaaS).
• Ubiquitous Connectivity: Seamless internet access everywhere, especially through mobile devices.
