10.1 Internet Architecture and Web Technologies

The internet's architecture is like a multi-layered cake, with each layer handling specific tasks. From the application layer that lets apps talk to networks, down to the physical layer that deals with cables and connectors, it's a complex system working together seamlessly.

Web technologies are the building blocks of the online world we interact with daily. HTML structures content, CSS makes it look pretty, and JavaScript adds interactivity. Together, they create the dynamic web experiences we've come to expect.

Internet Architecture

Components of internet architecture

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• Application layer enables communication between applications and the network using protocols like HTTP (web browsing), FTP (file transfer), SMTP (email), and DNS (domain name resolution)
• Transport layer provides end-to-end communication and data delivery using protocols such as TCP (reliable, connection-oriented) and UDP (unreliable, connectionless)
• Network layer responsible for routing packets across networks using protocols like IP (addressing and routing), ICMP (error reporting), and IGMP (multicast group management)
• Data link layer handles node-to-node communication within a network using protocols such as Ethernet (wired LANs), Wi-Fi (wireless LANs), and PPP (point-to-point connections)
• Physical layer defines physical characteristics of network components including cables (coaxial, fiber optic), connectors (RJ45, SC), and signal specifications (voltage levels, modulation schemes)

Data transmission via internet protocols

• Data divided into smaller packets for efficient transmission
• Each packet contains source and destination IP addresses for routing
• Packets routed through the network independently, allowing for dynamic path selection
• TCP establishes a connection between sender and receiver
  1. Ensures reliable delivery of packets by using sequence numbers and acknowledgments
  2. Retransmits lost or corrupted packets to guarantee data integrity
• IP responsible for addressing and routing packets
  1. Packets forwarded from one router to another based on destination IP address
  2. Routers use routing tables and protocols (OSPF, BGP) to determine the next hop

Web Technologies

Web technologies: HTML, CSS, JavaScript

• HTML (Hypertext Markup Language) defines the structure and content of web pages using tags to create elements like headings (

  <h1>

  ), paragraphs (

  <p>

  ), and links (

  <a>

  )
• CSS (Cascading Style Sheets) describes the presentation and styling of HTML elements controlling layout (positioning, margins), colors (text, background), and fonts (family, size)
• JavaScript programming language for creating interactive and dynamic web pages enabling user interaction (form validation, event handling), content updates without page reloads (AJAX), and complex web applications (single-page apps, progressive web apps)
• Key differences: HTML focuses on content structure, CSS on visual presentation, and JavaScript on behavior and interactivity; HTML and CSS are declarative languages, while JavaScript is a full-fledged programming language

Impact of web standards

• Web standards ensure consistency and interoperability defined by organizations like W3C (World Wide Web Consortium) providing guidelines for HTML, CSS, and other web technologies
• Benefits of adhering to web standards:
  • Improved accessibility for users with disabilities by using semantic HTML tags (

    <nav>

    ,

    <article>

    ) and ARIA attributes enabling assistive technologies (screen readers, braille displays) to interpret web content
  • Better cross-browser compatibility ensuring consistent rendering and functionality across different browsers (Chrome, Firefox, Safari) and devices (desktop, mobile)
  • Easier maintenance and development as standardized code is more readable, reusable, and future-proof
• Accessibility guidelines (WCAG - Web Content Accessibility Guidelines) provide recommendations for making web content more accessible including provisions for sufficient color contrast, keyboard navigation support, and alternative text for images