Network Overview
Introduction to Network Concepts
This document provides a foundational understanding of computer networking. Networks are essential for communication and data sharing between devices, forming the backbone of modern technology.
We will explore key concepts, protocols, and architectures that enable devices to connect and interact across local and global scales.
Core Components of a Network
A typical network consists of several fundamental components:
- Devices (Nodes): These are the endpoints that send or receive data. Examples include computers, servers, smartphones, and IoT devices.
- Network Interface Controllers (NICs): Hardware components that allow devices to connect to a network medium.
- Transmission Media: The physical or wireless pathways over which data travels. This includes Ethernet cables, fiber optics, and radio waves (Wi-Fi).
- Networking Devices: Hardware that manages and directs data traffic. Common examples include:
- Routers: Connect different networks and forward data packets between them.
- Switches: Connect devices within a local network (LAN) and forward data efficiently to the intended recipient.
- Modems: Convert digital signals from a computer to analog signals for transmission over telephone lines or cable, and vice versa.
- Protocols: A set of rules that govern how devices communicate. These define the format, order, and error-checking of messages.
Network Topologies
Network topology refers to the arrangement of the elements (links, nodes, etc.) of a communication network. Common topologies include:
- Bus Topology: All devices are connected to a single central cable. Simple but prone to failure if the main cable is damaged.
- Star Topology: All devices are connected to a central hub or switch. More robust than bus topology; failure of one cable only affects one device.
- Ring Topology: Devices are connected in a circular fashion, with data passing from one device to the next.
- Mesh Topology: Every device is connected to every other device. Highly redundant but complex and expensive to implement.
- Hybrid Topology: A combination of two or more topologies.
Network Types
Networks can be categorized by their geographical scope:
- Local Area Network (LAN): Covers a small geographical area, such as an office building or home. Typically high-speed.
- Wide Area Network (WAN): Spans a large geographical area, connecting multiple LANs. The Internet is the largest example of a WAN.
- Metropolitan Area Network (MAN): Covers a city or a large campus.
- Personal Area Network (PAN): Used for communication among devices close to a single person, such as Bluetooth connections.
The OSI Model and TCP/IP Model
To standardize network communication, several conceptual models have been developed. The most influential are the OSI (Open Systems Interconnection) model and the TCP/IP model.
OSI Model (7 Layers)
A theoretical framework that defines network communication in seven distinct layers:
- Physical: Transmission of raw bit streams.
- Data Link: Error detection and correction on the physical link.
- Network: Logical addressing and routing of packets.
- Transport: End-to-end communication and reliability (e.g., TCP, UDP).
- Session: Managing communication sessions between applications.
- Presentation: Data formatting, encryption, and compression.
- Application: Network services directly available to end-user applications.
TCP/IP Model (4 or 5 Layers)
A more practical model that forms the basis of the Internet:
- Link Layer (or Network Interface Layer): Combines OSI's Physical and Data Link layers.
- Internet Layer: Corresponds to OSI's Network layer (e.g., IP protocol).
- Transport Layer: Corresponds to OSI's Transport layer (e.g., TCP, UDP).
- Application Layer: Combines OSI's Session, Presentation, and Application layers (e.g., HTTP, FTP, DNS).
Key Protocols
Protocols are the language of networks. Some of the most fundamental include:
- IP (Internet Protocol): Responsible for addressing and routing packets across networks.
- TCP (Transmission Control Protocol): Provides reliable, ordered, and error-checked delivery of data.
- UDP (User Datagram Protocol): Provides a simpler, faster, but less reliable connectionless datagram service.
- HTTP (Hypertext Transfer Protocol): The foundation of data communication on the World Wide Web.
- DNS (Domain Name System): Translates human-readable domain names into IP addresses.
For a deeper dive into specific protocols like TCP/IP and HTTP, please refer to the respective sections.