Comprehensive Study Notes on Networks

Topic 3: Networks

Network Architecture

• WAN (Wide Area Network): Connects geographically dispersed hosts, typically across regions or nations, often consisting of multiple LANs linked by leased lines.

• LAN (Local Area Network): A network confined to a small geographic area, such as within a building or campus; uses wired communications protocols like Ethernet.

• Intranet: A private network that uses web technologies but restricts access to users within an organization. Hosted internally.

• Extranet: An extension of an intranet that provides limited access to selected outside users, such as customers or suppliers.

• Internet: A global network of networks using Internet Protocol (IP) to connect millions of private, public, academic, business, and government networks.

Types of Networks

3.1.1 Identify Different Types of Networks

• Definition of a Network: A computer network is a collection of computer systems and hardware devices linked through communication channels for facilitating communication and resource sharing among users.

• Categorization: Networks are categorized based on characteristics such as size, range, and type of connection.

Different Types of Networks

• LAN (Local Area Network):

  • Example: School or business networks

  • Characteristics: Confined to one building, uses wired protocols (e.g., Ethernet).

• WLAN (Wireless Local Area Network):

  • Explanation: Similar to LAN but utilizes wireless technologies (e.g., WiFi).

• VLAN (Virtual Local Area Network):

  • Definition: A subgroup of computers on a LAN treated as a separate network for security or access control without requiring physical hardware changes.

  • Comparison: More cost-effective and flexible than physical isolation.

• WAN (Wide Area Network):

  • Characteristics: Connects geographically distant hosts; often comprises LANs linked by leased lines.

• SAN (Storage Area Network):

  • Explanation: A specialized network for storage devices, not typically accessible from the main LAN (predominantly high-capacity storage).

• PAN (Personal Area Network):

  • Definition: Short-range networks for personal devices (e.g., smartphones, tablets) using Bluetooth.

Intranet, Extranet, Internet

• Intranet:

  • Definition: A private internal network similar to the internet but restricted to an organization.

• Extranet:

  • Definition: An intranet with controlled access for select users outside the organization.

• Internet:

  • Definition: A vast network of interconnected networks using IP, supporting services like the World Wide Web, email, and more.

Basic Network Components

• Hub: A central device that connects multiple computers in a network.

• Router: Routes data between different networks and manages traffic.

• Switch: Connects devices within a LAN and filters traffic.

• Bridge: Connects and filters traffic between two or more networks.

• Wireless Access Point: Provides wireless connections to devices.

Network Architectures

Client–Server Architecture

• Server: A program or computer that provides services to client requests over a network.

  • Software Defined: Listens for client requests on specific ports and provides responses.

  • Hardware: Dedicated machine optimized for service delivery, often with enhanced processing and storage capabilities.

• Client: A computer or terminal that accesses services and resources offered by the server.

  • Used in: Network architectures relying on a centralized server for providing services and resources.

Peer-to-Peer Network Architecture

• Description: All computers are interconnected without a central server.

• Security: Generally less secure since each node must secure its own data.

• Speed: Potential for faster speeds when optimized algorithms are applied, as seen in torrenting applications.

Internet Service Providers (ISP)

• Definition: Organizations that offer services related to accessing the internet, web hosting, and data facilities.

  • Types of Providers:

  • Tier 1 Providers: Major companies that own the network infrastructure without needing services from other providers directly.

  • Various Connection Methods: Includes Dial-up, ISDN, ADSL, T1, Gigabit Ethernet, and Fiber Optic.

  • Connection Speed: Ranges from slow (dial-up) to fast (fiber optics).

Virtual Private Networks (VPN)

• Definition: A secured network that uses the public internet to connect remote users as if they were on a private network; utilizes encryption and other security measures.

• Components:

  • Encryption Protocols: Such as SSL and TLS for securing data.

  • Tunneling Protocols: Protocols like SSTP, IPSec, and OpenVPN that encapsulate data for secure transport.

• Advantages:

  • Enables secure remote access to resources such as files, printers, and databases over the internet.

  • Cost-effective, avoiding the need for expensive leased lines.

• Disadvantages:

  • Security risks due to the public nature of the internet requiring robust encryption and security protocols.

Importance of Standards in Networking

3.1.2 Outline the Importance of Standards

• Role of Standards:

  • Provide a common framework for compatibility among devices from different manufacturers.

  • Facilitate communication and interoperability between diverse networking products.

  • Promote efficiency and reduce errors in data transmission and processing.

Communication Over Networks: Layered Model

3.1.3 Describe Communication Layers

• The OSI Model: A conceptual framework that standardizes communications in telecommunication or computing systems, broken into seven layers.

  • Purpose: Each layer focuses on specific networking functions, allowing independence and abstraction.

  • Four Important Layers:

  • Application Layer: Manages user interface and application-level functions (e.g., HTTP).

  • Transport Layer: Ensures data transfer reliability and segmentation (e.g., TCP).

  • Network Layer: Manages addressing and routing (e.g., IP).

  • Physical Layer: Defines electrical/physical specifications for data transmission (e.g., Ethernet).

• Packet Structure: Each layer may encapsulate data packets, each level's packets may have distinct terminologies (e.g., frame, datagram).

Networking Technologies for VPN

3.1.4 Identify Technologies Required for a VPN

• Encapsulation and Encryption: Security for the data transmitted via public internet.

• Tunneling Protocols: Essential for securing data synchronization over diverse networks.

Data Transmission Characteristics

3.1.6 Define Terms and Explain Importance of Protocols

• Definition of Protocol: A standardized set of rules for data transfer and communication between devices in a network.

• Importance of Protocols:

  • Ensure data integrity, reliability, and proper transmission rates while avoiding data collisions and congestion.

  • Enable error checking mechanisms and establish communication protocols among varied hardware.

Factors Affecting Data Transmission Speed

3.1.9 Explain Variability of Data Transmission Speeds

• Factors Influencing Speed:

  • Bandwidth: Maximum data rate; higher bandwidth correlates with faster speeds.

  • Network Congestion: Reduced speeds due to high demand exceeding bandwidth.

  • Latency: Time faced due to distance or hardware routing time; increased physical distance leads to slower transmissions.

  • Packet Loss: The need for retransmission incurs time and reduces effective speed.

  • Protocols: Variability in protocol efficiency impacts overall transmission speed.

  • Physical Medium: Cable types influence data transmission rates; fiber optic is typically faster than copper.

  • Distance: Greater distances can increase latency, affecting transmission speeds adversely.

  • Network Hardware: Older hardware may not maintain high-speed efficiency.

  • Interference in Wireless Networks: Disruptions from environmental factors diminish speed and reliability.

Data Compression Necessity

3.1.8 Explain Necessity of Data Compression

• Purpose of Data Compression: Achieving efficient data handling by reducing redundancy in bytes.

• Types of Compression:

  • Lossless Compression: Original data is preserved, reversible.

  • Lossy Compression: Works on the principle of reducing size by discarding some data.

Transmission Media Characteristics

3.1.10 Describe Characteristics of Different Transmission Media

• Guided Transmission Media: Wired methods, including twisted-pair cables, coaxial cables, and fiber-optic cables.

• Unguided Transmission Media: Wireless methods utilizing electromagnetic spectrum, such as WiFi and Bluetooth.

3.1.11 Outline Wireless Network Advantages and Disadvantages

• Advantages of Wireless Networks:

  • Enhanced mobility and convenience, no physical cables.

• Disadvantages:

  • Susceptibility to signal interference, crowded channels affecting performance.

Packet Switching and Communication

3.1.12 Explain Packet Switching Communication

• Packet Switching:

  • Interest: Data is broken into packets, efficiently routed through available paths.

  • Control Information: Headers indicate destination and data length; payload contains actual data.

• Circuit Switching: A dedicated communication path is established, unlike the flexible routing in packet switching.

Advantages and Disadvantages of Wireless Networks

• Advantages: Flexibility, easy device additions, and broad coverage.

• Disadvantages: Possible signal degradation and vulnerability to eavesdropping.

Security Methods

3.1.15 Describe Network Security Methods

• Usernames/Passwords: Identification and authentication of users.

• Encryption: Securing unauthorized data access.

• Antivirus: Protect against various cyber threats, often at network entry points.

• Firewall: Monitors network traffic and blocks unapproved connections.

• Physical Security: Physical barriers like locks and surveillance.

Attacks Overview

• Types of Hacking Attacks: Denial of Service, Man-in-the-Middle, Phishing, Trojan Horse, Spoofing, Spyware.

Network Topologies

3.1.16 Network Topologies

• Types of Topologies:

  • Single Isolated: Point-to-point connection between two systems.

  • Bus Topology: All devices connect to a single cable; easy to expand but reliant on the main cable functioning.

  • Star Topology: Central hub or switch connected to all devices; secure and efficient but dependent on central device.

  • Mesh Topology: Data can route through various paths; very flexible and resilient but complex to maintain.

  • Hybrid Topology: Combining different topological structures, capable of handling varied loads, but complex to set up and manage.

Summary: Key Concepts

• Data Packets: Fundamental units of network communication; consist of headers and payloads.

• Protocols: Necessary for clarity and reliability in communication.

• VPNs: Provide secure remote access, especially beneficial in contexts like telecommuting.