CSC Chapter 4 Notes

Chapter 4: Networking and the Internet

4.1 Network Fundamentals

  • Definition: Networks consist of interconnected devices that communicate with each other.

  • Major Components:
      - Local Area Network (LAN): A network covering a small geographical area, such as a home or office.
      - Metropolitan Area Network (MAN): A network that covers a larger geographic area than a LAN but is smaller than a WAN, typically a city.
      - Wide Area Network (WAN): A network that covers a broad area, potentially global, such as the Internet.

  • Ownership:
      - Closed Networks: Proprietary networks managed by a single entity.
      - Open Networks: Publicly accessible networks that can be utilized by anyone.

  • Comparison of Cell Phone Networks and the Internet: Cell networks operate on specific protocols and infrastructure while the Internet provides a broader open platform.

4.2 Network Topologies

  • Definition of Topology: The arrangement of different elements (links, nodes) in a network.

4.2.1 Topologies Types

  • Bus Topology:
      - Described as a single central cable (the bus) to which all network devices are connected.
      - Layout:            Computer                 Computer

  • I I
      —————————————————————-        

  • I I I

  •  Computer         Computer                     Computer

  • Star Topology:
      - All devices are connected to a single central hub or switch.
      - Layout:
                           Computer
                 / | \
          Computer Computer Computer

                        \        I /

                               Computer

4.3 Protocols

  • Definition of Protocols: A set of rules for communication between network devices.

  • Key Protocols Covered:
      - TCP/IP: Transmission Control Protocol/Internet Protocol - foundational suite for Internet communications.
      - HTML: HyperText Markup Language used for creating web pages.
      - URL: Uniform Resource Locator, the address of a web resource.
      - FTP: File Transfer Protocol for transferring files.
      - HTTP: HyperText Transfer Protocol for transferring hypertext over the web.

4.4 Connecting Networks

  • Device Functions:
      - Repeater: Extends the range of a network by regenerating signals.
      - Bridge: Connects two separate networks that use the same protocol.
      - Switch: Connects multiple devices on a network and filters data for efficient communication.
      - Router: Connects different networks, can route data between incompatible networks, creating an "internet" of interconnected networks.

4.5 Building Networks

  • Building a Large Bus Network: Combine smaller bus networks effectively to manage increased traffic and devices.

  • Router Connections: Routers can connect Wi-Fi networks and Ethernet networks, facilitating communication between different network standards.

4.6 Inter-Process Communication

  • Client-Server Model:
      - Server: A dedicated machine that provides resources and services to clients.
      - Client: A machine that requests resources or services.
      - Characteristics: One server may handle many clients; the server must be active continuously, initiating communication from clients.

  • Peer-to-Peer (P2P) Communication:
      - Two devices communicate as equals without requiring a central server.
      - Characteristics: Peer processes might be temporary or short-lived.

4.7 Distributed Systems

  • Definition: Systems where components are spread across multiple computers connected through a network.
      - Distributed Databases: Systems such as airline reservation systems that store data across different locations.
      - Cluster Computing: Increases computational power by linking multiple computers.
      - Grid Computing: Allows many computers to work together on a task, particularly during periods of downtime.
      - Cloud Computing: Applications and data are stored on remote servers, accessible over the Internet.

4.8 The Internet

  • Definition: A global network of interconnected computers originating from a research project aimed at creating a resilient means of communication.

  • Characteristics:
      - Decentralized: No single point of control exists.
      - Open: Anyone can access the Internet and create services.
      - Distributed: Data and tasks are spread across many locations.

4.9 Internet Architecture

  • Internet Service Provider (ISP): A company that provides access to the Internet.
      - Tiers of ISPs:
        - Tier-1: Major backbone providers.
        - Tier-2: Connect to Tier-1 and provide access to consumers.
      - Access ISP: Offers connectivity options such as:
        - Dial-up via traditional telephone lines.
        - Cable connections.
        - DSL (Digital Subscriber Line).
        - Fiber optic connections.
        - Wireless connections.
        - Cellular connections.

4.10 Internet Addressing

  • IP Addresses: Unique identifiers for devices on a network, represented as 32 bits (IPv4) or 128 bits (IPv6) in dotted decimal notation.

  • Mnemonic Addressing:
      - Domain Names (e.g., www.example.com) are easier to remember than numerical IP addresses.
      - Top-Level Domains (TLD): Categories for domain names, such as ".com", ".org", ".edu", and national codes like ".uk", ".au".

  • Domain Name System (DNS): A system that translates domain names into IP addresses.
      - Components: Includes name servers that respond to DNS queries (DNS lookups).

4.11 Internet Corporation for Assigned Names & Numbers (ICANN)

  • Functions:
      - Allocates IP addresses to ISPs, who in turn assign them into their service regions.
      - Oversees domain name registrations and ensures they are recorded in DNS registries.
      - Users must register a domain name with a registrar (e.g., register.com, active-domain.com, netsol.com) to secure their presence on the Internet.

4.12 Demonstrations for DNS Importance

  • DNS Lookup Process:
      1. DNS lookup by the user to find the IP address of a domain (e.g., amazon.com).
      2. DNS server returns the corresponding IP address.
      3. User connects to the IP address for access.

  • Direct IP Access Challenges:
      - Virtual Hosting: Multiple sites can share one IP address, complicating access via IP alone, as servers may not know which site to display.
      - Security Issues: Direct access raises security concerns; sites might block access to prevent potential threats.
      - Load Balancing: Direct IP access can bypass sophisticated traffic distribution mechanisms, leading to performance issues.

4.13 Traditional and Recent Internet Applications

  • Traditional Applications:
      - Email: Clients receive mail via servers using protocols like POP3 or IMAP.
      - File Transfer Protocol (FTP): Used for transferring files between computers.
      - Search Engines and Portals: Aggregate information and facilitate searches online.
      - Database Applications: Many modern sites are data-driven.

  • Recent Applications:
      - Voice Over IP (VoIP): Applications like Skype and Zoom.
      - Streaming Services: Platforms like YouTube and Netflix for audio and video content.
      - Live Streaming: Services for real-time broadcasting.
      - Peer-to-Peer File Sharing: Distribution of files directly between users without an intermediary.
      - Mobile Apps: Applications requiring responsive computing power and connectivity.
      - Cloud Services: Applications hosted remotely, accessible over the Internet.

4.14 World Wide Web

  • Definition: A vast information system that utilizes hypertext and HTTP for accessing resources.

  • Browser Function: Retrieves documents from web servers using the client-server model.

  • Documents Identification: Resources are uniquely identified by URLs.

4.15 Hypertext Document Format

  • Structure: Documents formatted as text files containing specific tags for web browser interpretation.
      - Tags Examples:
        - <h1>: Starts a level one heading.
        - <p>: Introduces a new paragraph.
        - <a href="...">: Creates links to other pages.
        - <img src="...">: Inserts images into documents.

4.16 Extensible Markup Language (XML)

  • Definition: A flexible markup language designed for creating markup languages, descending from SGML.

  • Functionality: Facilitates a World Wide Semantic Web by allowing structured data representation.

4.17 Client Side Versus Server Side Operations

  • Client-Side Activities: Include HTML, JavaScript, CSS, Adobe Flash, and Java applets executed on the user's web browser.

  • Server-Side Activities: Include technologies like PHP and Java Servlets, which manage database interactions and application logic remotely.

4.18 Internet Software Layers

  • Application Layer: Constructs the message with the recipient's address.

  • Transport Layer: Segments the message into packets for transmission.

  • Network Layer: Manages routing of packets through the Internet.

  • Link Layer: Oversees the physical transmission of packets.

4.19 Packet Switching

  • Definition: Method of data transmission where data is broken into packets that are routed independently and reassembled at the destination, in contrast to circuit switching, which maintains a constant connection.

  • Advantages of Packet Switching: Efficient use of network resources as it does not monopolize connections, allowing for better bandwidth allocation.

4.20 TCP/IP Protocol Suite

  • Overview: The foundational protocols governing packet switching in networks.
      - Transport Layer Protocols:
        - TCP (Transmission Control Protocol): Manages packet sequence and ensures complete data transfer.
        - UDP (User Datagram Protocol): Provides a lightweight alternative without error-checking features.
      - Network Layer Protocols:
        - IP (Internet Protocol): Assigns addresses to packets and facilitates their routing.
          - IPv4: Common IP format using 32-bit addresses.
          - IPv6: Newer format using 128-bit addresses for more available unique identifiers.

4.21 Security Concerns

  • Types of Attacks:
      - Malware: Includes viruses, worms, Trojan horses, and spyware that can invade networks and systems.
      - Phishing: Deceptive attempts to acquire sensitive information through fraudulent communication.
      - Hacking: Unauthorized access to systems for malicious purposes.
      - Denial of Service: Attacks aimed at disrupting services by overwhelming resources.
      - Spam: Unsolicited messages sent in bulk, cluttering communication channels.

  • Protection Measures:
      - Firewalls: Devices or software that control incoming and outgoing network traffic.
      - Spam Filters: Systems that identify and remove unwanted messages.
      - Proxy Servers: Intermediary servers that can serve various functions including anonymity and security.
      - Antivirus Software: Tools designed to detect and eliminate malicious software.
      - Encryption: Processes for securing data, including the use of SSL, HTTPS, and SFTP for secure communications.

4.22 Encryption Techniques

  • Public-Key Encryption:
      - Public Key: Used to encrypt messages. Available to anyone who wishes to send a secure message.
      - Private Key: Exclusive to the receiver, used to decrypt the received messages.

  • Certificates and Digital Signatures: Provide authentication and assurance regarding the identity of the entities exchanging information.

4.23 Good Personal Security Practices

  • Lock your computer or log off when not in use.

  • Avoid writing down passwords.

  • Be cautious of unsolicited requests for information.

  • Do not open suspicious attachments or links.

  • Maintain an up-to-date personal firewall.

  • Regularly update antivirus software to protect against threats.