Internet and the World Wide Web

What is the Internet?

• The Internet is a global system of interconnected computer networks using the TCP/IP protocol suite.
• It supports a wide range of information resources and services, including the WWW and email.
• Traditional media like telephone, music, film, and television have been reshaped by the Internet.

History of the Internet

• The Internet's origins are traced back to the 1960s with the U.S. government's ARPANET, designed to be robust and fault-tolerant.
• ARPANET was used for data sharing between universities and government facilities.
• The National Science Foundation (NSF) and NASA further developed networks in the 1980s.
• NSFNET was decommissioned in 1995 and replaced by commercial Internet Service Providers, leading to popularization and widespread use.

Modern Infrastructure

• High-speed fiber optic lines (OC lines) connect regions, cities, and continents.
• Examples of OC line speeds:
  • OC-1: 51.84 Mbit/s
  • OC-3: 155.52 Mbit/s
  • OC-12: 622.08 Mbit/s
  • OC-24: 1,233.16 Mbit/s
  • OC-48: 2,405.37 Mbit/s
  • OC-192: 9,621.50 Mbit/s
  • OC-768: 39,813.12 Mbit/s (39.8 Gbit/s)
• Undersea fiber optic cables connect continents, with some spanning over 12,000 miles.

Governance

• No single entity owns the Internet; it is made up of networks owned by various organizations.
• ICANN directs the Internet Protocol address space and Domain Name System.
• The IETF standardizes core protocols like IPv4 and IPv6.
• The Internet Governance Forum (IGF) discusses Internet-related issues.

How the Internet Works

• The Internet facilitates communication through web browsing, email, and video.
• Two basic models for communication:
  • Circuit switching: Establishes a reliable, semi-permanent connection.
  • Packet switching: Data is broken into packets and sent independently (TCP/IP).

Client-Server vs. Peer-to-Peer

• Client-server: Servers provide resources, and clients request them.
• Peer-to-peer (P2P): Peers share resources directly without central coordination.

Protocols

• Protocols are rules for communication between computers.
• Common protocols:
  • HTTP: WWW communication
  • SMTP: Email
  • FTP: File transfer
  • POP3: Web-based email clients
  • VoIP: Internet telephony

Networks

• LAN (Local Area Network): Connects computers in a local area.
• Internet: A global network of interconnected networks.
• Intranet: A network for local communication only.
• Extranet: Allows controlled access to select information on a network via the Internet.
• Communications can be secured using VPN technology and HTTPS.

Cloud Computing

• Cloud computing: Accessing server-based computational resources via a network.
• Applications and data are managed remotely by the cloud server.

Addressing

• URLs (Uniform Resource Locators) specify the location of resources and the retrieval mechanism.
• IP addresses are numeric addresses that uniquely identify machines.
• The Domain Name System (DNS) automatically looks up numeric addresses for URLs.

World Wide Web

• The WWW is a system of interlinked hypertext documents accessed via the Internet.
• It is one of the services that run on the Internet and consists of interconnected documents and resources linked by hyperlinks and URLs.
• Web pages are viewed using a web browser.