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Chapter 8: Topologies, Protocols & Web Services

8.1 Network Types

Depending on their geographical span, networks can be grouped into:

  1. PAN (Personal Area Network): Covers a very small area (up to a few meters). Usually connects personal devices like Bluetooth headphones to a smartphone, or a wireless mouse to a computer.
  2. LAN (Local Area Network): Spans a single building or a small geographical area, such as a school campus, office, or home. Very fast and privately owned.
  3. MAN (Metropolitan Area Network): Connects two or more LANs across a larger area, typically a city or a large campus. For example, a cable TV network.
  4. WAN (Wide Area Network): Covers vast geographical regions, such as countries or even spanning the globe. The Internet is the world’s largest WAN. They often use public infrastructure (like telephone lines or satellites).

8.2 Network Topologies

Topology refers to the physical or logical layout of a network.

  1. Bus Topology:
    • All devices are connected to a single central cable, called the main trunk or backbone.
    • Pros: Easy to install, uses the least cable, cheap.
    • Cons: If the main cable breaks, the entire network fails. Hard to find where the fault is. Performance drops under heavy traffic.
  2. Star Topology:
    • All computers are connected to a central device, such as a Hub or Switch.
    • Pros: Most common and reliable. If one cable breaks, only that single computer goes down. Easy to add new devices. Easy to troubleshoot.
    • Cons: If the central Hub/Switch fails, the entire network crashes. Requires more cable than a Bus topology.
  3. Tree Topology (Hierarchical):
    • A combination of Bus and Star topologies. It relies on a central “root” node, with branches fanning out (like an inverted tree). Common in hierarchical large organizations.
    • Pros: Highly scalable. Easy to manage individual segments (branches).
    • Cons: If the main bus cable fails, the entire network drops. Complex to configure compared to Star.

8.3 Network Protocols

A protocol is a set of rules that computers use to communicate over a network.

  • HTTP (HyperText Transfer Protocol): Governs how web pages are transmitted over the Internet from web servers to your browser. Uses port 80.
  • HTTPS (HTTP Secure): A secure version of HTTP that encrypts data between the server and the client to protect sensitive information (like passwords or credit card numbers). Uses port 443.
  • FTP (File Transfer Protocol): Standard protocol used for transferring files between a client and a server on a computer network.
  • TCP/IP (Transmission Control Protocol / Internet Protocol): The foundational suite of protocols for the Internet.
    • TCP: Handles the reliable delivery of packets (breaking data down, verifying delivery, reassembling).
    • IP: Handles the physical addressing (routing) of packets so they reach the correct destination.
  • SMTP (Simple Mail Transfer Protocol): Used universally for sending email messages from an email client to an email server.
  • POP3 (Post Office Protocol version 3): Used for receiving/downloading emails from a server to a local client.
  • PPP (Point-to-Point Protocol): Used to establish a direct connection between two nodes (e.g., dial-up connection).
  • TELNET: An older protocol used for remote login into a computer over a network. Security is a concern because it sends data in plain text.
  • VoIP (Voice over Internet Protocol): Allows making voice calls using a broadband Internet connection instead of a regular analog phone line (e.g., WhatsApp calls, Skype).

8.4 Introduction to Web Services

The Internet provides the infrastructure, but various services run on top of it. One of them is the World Wide Web (WWW). The web consists of interconnected documents (web pages).

  1. HTML (HyperText Markup Language): The standard language used to create the structure and content of a web page.
  2. XML (eXtensible Markup Language): Used primarily to structure and transport data, rather than display it (like HTML). It allows users to define their own tags.
  3. URL (Uniform Resource Locator): The unique global address of a specific resource on the web (e.g., https://www.google.com/images/logo.png).
  4. Domain Name: A human-readable name that identifies an IP address on the Internet (e.g., google.com). This makes it easier for humans to remember addresses instead of memorizing numerical IP strings.
  5. Website: A collection of related web pages hosted under a single domain name.
  6. Web Browser: A software application (like Chrome, Firefox, Safari) used to access, retrieve, and display information from the World Wide Web.
  7. Web Server: A specialized computer or software program that stores website files and delivers them back to clients’ web browsers upon request over the Internet.
  8. Web Hosting: The business of providing storage space and access for websites on a web server so they are accessible on the Internet 24/7.