Computer Networks PDF

Introduction to Computer Networks Computer networks are the backbone of modern communication and computing. They enable devices to connect, share resources, and communicate efficiently, fundamentally transforming how we interact with technology and with one another. What is a Computer Network? A computer network is a collection of computing devices connected to share resources and communicate. These connections can be: Physical: Using wires such as coaxial, twisted-pair, or fiber optics. Wireless: Using radio waves, infrared signals, or satellites. Key Concepts: 1. Nodes / hosts: ○ Any device connected to a network, such as computers, printers, or IoT devices. 2. Bandwidth: ○ The data transfer rate, measured in bits per second (bps), determining how quickly data moves within the network. ○ Common units include Mbps (megabits per second) and Gbps (gigabits per second). 3. Protocols: ○ A set of rules governing data communication between devices. ○ Examples: HTTP: Facilitates web page requests. HTTPS: Secure version of HTTP, encrypting data in transit. FTP: Handles file transfers between systems. SMTP: Handles email sending. POP3/IMAP: Retrieve emails from mail servers. DNS: Resolves human-readable domain names into IP addresses. ARP: Maps IP addresses to hardware addresses. ICMP: Diagnoses network issues using tools like ping. Telnet/SSH: Remote access protocols for managing servers and devices. Types of Network Architectures 1. Client-Server Architecture: ○ A centralized model where servers provide resources, and clients request them. ○ Examples of servers: File Servers: Store and manage shared files. Web Servers: Deliver web pages and applications. ○ Challenges: 2 Single Point of Failure (SPOF): If the server crashes, the network ceases to function. Solution: Implement load balancing to distribute traffic across multiple servers, enhancing reliability and performance. 2. Peer-to-Peer (P2P) Architecture: ○ A decentralized model where all nodes (peers) share data and resources equally. ○ Benefits: Eliminates SPOF. Reduces dependency on centralized servers. ○ Drawbacks: Security risks due to unverified peers. Administrative challenges. Types of Networks 1. Local Area Network (LAN): ○ Covers a small geographic area, such as a single building. ○ Common topologies: Ring: Nodes form a closed loop, passing messages in one direction. Star: All nodes connect to a central hub. Bus: Nodes share a single communication line. 2. Metropolitan Area Network (MAN): ○ Spans a city or campus, interconnecting multiple LANs. ○ Often uses high-speed connections like fiber optics. 3. Wide Area Network (WAN): ○ Connects multiple LANs or MANs over large distances, such as cities or continents. ○ The Internet is the largest example of a WAN. Networking Hardware 1. Transmission Media: ○ Guided: Includes cables like coaxial, twisted-pair, and fiber optics. ○ Unguided: Wireless media, including radio waves and satellites. 2. Routers: ○ Forward data between different networks using routing tables. 3. Switches: ○ Connect multiple devices within the same network, ensuring efficient data delivery. 4. Network Interface Cards (NICs): ○ Enable devices to connect to a network by converting data into transmittable signals. 5. Firewalls: 3 ○ Protect networks by filtering incoming and outgoing traffic based on predefined rules. 6. Load Balancers: ○ Distribute incoming network traffic across multiple servers to enhance performance and reliability. ○ Prevents overloading a single server, ensuring high availability and faster response times. Network Communication 1. Packet Switching: ○ Divides data into smaller units (packets) for transmission. ○ Packets take independent routes and are reassembled at the destination. 2. Latency: ○ The time delay between sending a request and receiving a response. ○ Low latency is crucial for real-time applications like video conferencing. The Internet Backbone and ISPs 1. Internet Backbone: ○ A high-speed, high-capacity network of interconnected routers and links that forms the core of the Internet. ○ Composed of fiber-optic cables and major network nodes managed by Tier 1 ISPs. 2. Internet Service Providers (ISPs): ○ Provide access to the Internet for individuals and organizations. ○ Types of ISPs: Tier 1 ISPs: Own and operate the Internet backbone. Tier 2 ISPs: Connect to Tier 1 networks and provide regional coverage. Tier 3 ISPs: Offer access directly to end-users. TCP/IP Suite 1. Transmission Control Protocol (TCP): ○ Ensures reliable packet delivery by checking for errors and resending lost packets. 2. User Datagram Protocol (UDP): ○ Provides faster but less reliable data transmission, suitable for streaming. Domain Names and IP Addresses 1. Domain Names: ○ Human-readable identifiers (e.g., example.com). ○ Translated into IP addresses by the Domain Name System (DNS). 2. IP Addresses: 4 ○ Unique numeric addresses identifying devices on a network. ○ IPv4: 32-bit addresses (e.g., 192.168.1.1). ○ IPv6: 128-bit addresses, offering more combinations to meet growing demands. ○ Advantages of IPv6 over IPv4: Address Space: IPv6 offers 2128 addresses compared to IPv4’s 232, accommodating the exponential growth of connected devices. Built-in Security: IPv6 includes IPsec, ensuring secure data transmission. Simplified Network Configuration: IPv6 supports automatic address configuration, reducing manual setup. Improved Routing: IPv6 reduces the size of routing tables and enhances performance with hierarchical addressing. Conclusion Computer networks are essential for connecting devices, facilitating communication, and sharing resources. By understanding networking architectures, hardware, and communication protocols, we can optimize and secure these systems for both personal and professional use. 5

Computer Networks PDF

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