Lecture 7: Internet and Networks

Lecture 7: Internet and Networks

Previous Lecture Review

  • Operating Systems
    • What is an operating system?
    • What are the fundamental benefits of an operating system?
    • Examples of operating systems
    • Understanding the environment of a Windows operating system

Lecture Contents

  • Internet and Networks
    • What is the Internet?
    • What does the Internet offer?
    • Requirements for connecting to the Internet
    • Most popular Internet services
    • What is a network?
    • Types of networks

Internet Definition

  • Internet: Short for International Network, a network of networks composed of a vast number of interconnected networks, encompassing a massive number of computers distributed across the globe.
  • If a node in the network fails, data transmitted over the Internet will find an alternative route to its destination.
  • The Internet is not centralized; no single computer controls it globally.

Types of Connection Lines

  • Typically, Internet connection is established through telephone lines via a Modem, which is connected to an Internet Service Provider (ISP).
  • Alternatively, connection can be achieved using Integrated Services Digital Network (ISDN) through wires or satellite.
  • Digital Service Line (DSL) offers high speed compared to modem speed via telephone lines.

Modem Details

  • A modem is a telephone communication card for the computer, used to access telephone networks and, consequently, the Internet.
  • It is a device that converts analog signals to digital signals and vice versa.
  • Computers deal with digital signals, while telephone lines handle analog signals, enabling computers to connect with each other via telephone lines.

Advantages of the Internet

  • World Wide Web (WWW):
    • The most popular service, allowing users to access information in various forms, such as text documents, audio files, or video files, through web pages accessed via browsers and the HTTP protocol.

Examples of WWW Specialized Sites

  • Electronic libraries and scientific journals
  • Websites of various institutions
  • Online shopping sites
  • News sites
  • Search engines like Google
  • Social networking sites

More Internet Advantages

  • Email:
    • Enables rapid communication between users.
  • File Transfer Protocol (FTP):
    • Allows users to exchange and download files, aiding researchers in data transfer over the network.

Internet Relay Chat

  • Enables users to communicate via text, audio, or video.
  • Used in various fields such as:
    • Distance learning
    • Instant communication via messenger programs
    • Communication via social media platforms like Facebook and Twitter

Requirements for Internet Connection

  • If not connected through an institution or university network, the following are needed:
    1. Computer
    2. Modem
    3. Telephone line and account with an Internet Service Provider
    4. Internet connection program
    5. Internet browser

Internet Browser

  • An internet browser is a program that allows access to the World Wide Web (WWW) for browsing websites.
  • Examples of browsers:
    1. Internet Explorer
    2. Mozilla Firefox
    3. Opera
    4. Chrome

Internet Addresses

  • Every website has an address starting with the information exchange protocol http, followed by the organization's name and an extension indicating the nature of the organization. Sometimes, a country code is added (e.g., Sudan sd, Saudi Arabia sa).

Common Domain Extensions

ExtensionNature of Organization
comCommercial and industrial companies
eduEducational institutions
govNon-military government departments
milMilitary entities
netNews networks and service centers
orgOther organizations
intOrganizations affiliated with the United Nations
infoInformation organizations

Examples of Institutional Websites

  • Al Jazeera News Network: www.Aljazera.net
  • Sudanese Ministry of Higher Education: www.uohe.edu.sd
  • Saudi Arabia's General Organization for Technical and Vocational Training: www.gotevot.edu.sa
  • Kutub Books Library: www.kutub.info
  • Sudan TV Channel: www.sudantv.gov.sd
  • Faisal Islamic Bank of Sudan: www.fibsudan.com

Computer Networks

  • A network is a group of computers and other devices connected to each other, enabling a large number of users to share resources such as software and hardware. It also serves as an electronic communication medium between individuals.

Benefits of a Network

  • Sharing files within the network and transferring them without external storage media.
  • Sharing devices within the network such as printers.
  • Sharing programs stored on a computer or server on the network.
  • Easy voice and video communication via communication programs.
  • Easy correspondence via email.

Components of a Computer Network

  • A network consists of hardware and software components.
    1. Network Hardware:
      • Includes:
        • Servers
        • User devices
        • Network cards
        • Connecting cables
        • Wired and wireless connecting devices
    2. Network Software:
      • Includes:
        1. Server operating systems
        2. Protocols
        3. Sharing applications

Types of Networks

  • Based on Geographical Area:
    • Local Area Network (LAN)
    • Metropolitan Area Network (MAN)
    • Wide Area Network (WAN)
  • Based on Means of Communication and Connection:
    • Wired Networks
    • Wireless Networks

Network Types by Geographic Area

  1. Local Area Network (LAN):

    • Initially, networks consisted of a small number of connected devices and a printer.
    • Current technology allows LANs to adapt and handle a much larger number of users but still operates within a limited area.
    • LANs are usually contained within an office or a group of offices inside a single building.

  2. Metropolitan Area Network (MAN):

    • Designed to connect an entire city.
    • Extends to a larger area than a LAN but smaller than a WAN.
    • Maintains the structure of a LAN, using dedicated high-speed communication lines with specific standards.

  3. Wide Area Network (WAN):

    • Spans vast areas or continents.
    • The Internet belongs to WANs.
    • Uses both public and private communication means (telephone lines).
    • Several ways to connect a WAN, including leased lines, radio waves, satellites, microwave, or telephone network technology.
    • The Internet is the largest existing WAN.

Modern Network Connection Methods

  1. Peer-to-Peer Networks
  2. Client-Server Networks

  • Peer-to-Peer Networks:

    • Consist of devices and systems with the same capabilities and functions.
    • Allow desktop and laptop computers to act as servers and share files with other devices on the network.
    • Examples include home networks and small office networks that do not require a high-capacity server.
    • Any device on the network can be a server or a client.

  • Client-Server Networks:

    • Consist of a powerful computer called a Server, which provides services in terms of storage, programs, and network resources to devices that request them (Clients).
    • The operation of client devices is linked to the server.

Network Types by Communication and Connection Methods

  1. Wired Networks
    • Use cables to connect and transfer data between different network devices.
  2. Wireless Networks
    • Use wireless connection technologies such as Wi-Fi and Bluetooth to connect and transfer data.

Wired and Wireless Media

  • Wired Medium:
    • Uses cables for signal transmission.
    • Can be metal wires or optical fibers.
  • Wireless Medium:
    • Uses the atmosphere as a medium for signal transmission.
    • Includes radio waves, microwaves, and infrared rays.

Network Topologies

  • Network topologies vary depending on how computers are connected to each other.
  • Three main types:
    • BUS (Linear Network)
    • RING (Ring Network)
    • STAR (Star Network)

Network Topologies Details

  • BUS Topology (Linear):
    • Consists of a single cable to which all devices are connected.
    • Any device can send data to any node (device).
    • The message is transmitted to all nodes on the network, but only the intended recipient can read it.
    • The sender controls the network until the transmission is complete.
    • Also known as a linear bus network.
    • Features simplicity, flexibility in installation and operation, and ease of maintenance.
    • Network operation is not interrupted if one of the computers fails.

Disadvantages of BUS Topology:

  • The number of nodes on the network affects performance speed.

  • If the main cable fails, the entire network fails.

  • Difficulty in identifying problems on the network.

  • Not suitable for large network expansion.

  • RING Topology:

    • Computers are connected to each other in a ring shape.
    • Does not have a main transmission medium or HUB.
    • Each device acts as a transmission medium for data.
    • Easy to install but difficult to troubleshoot.
    • The network stops completely if the cable is interrupted.

  • STAR Topology:

    • Computers are connected to a central connection unit called a hub or switch using a separate cable for each device.
    • The hub acts as a collection point and forwards data to other computers on the network.
    • Considered one of the best types of networks because:
      • Easy to add or isolate computers on the network.
      • Isolating any part of the network does not affect the rest of the parts.
      • Easy to troubleshoot.
    • Disadvantages include:
      • Centralized control.
      • Slow data transfer.
      • Failure of the hub leads to complete network failure.

Star Topology Connection Variations

  • Other forms of connection exist.

Network Services

  • Key services include:
    • Sharing information with other computers.
    • Printing documents on a printer connected to another computer.
    • Accessing the Internet.
  • To perform these services, your computer must be connected to the network.