Understanding Computer Networks: Architectures, Protocols, and Management

Posted on Aug 27, 2024 in Computers

Module 01: Computer Networks

A computer network is a collection of interconnected computers that communicate and share data, applications, and hardware resources like file servers and printers. Networks can vary in size, functionality, and location.

LAN

Coverage Area: Covers a small, localized area such as a home, office, or campus.
Speed: Generally offers high-speed data transfer, often faster than WANs.
Cost: Less expensive to set up and maintain since it requires fewer resources.
Security: Easier to manage and secure due to its limited geographical scope.
Ownership: Typically owned, managed, and maintained by a single organization or individual.
Connection Type: Typically uses Ethernet cables, Wi-Fi, or both for connecting devices within the network.
Reliability: Usually more reliable with fewer interruptions since it’s confined to a smaller area and controlled environment.

WAN

Coverage Area: Spans a large geographical area, connecting different cities, countries, or even continents.
Speed: Usually slower than LANs due to the vast distances and the type of connections used.
Cost: More expensive to set up and maintain, involving complex infrastructure and service provider fees.
Security: More challenging to secure because of its large scope and exposure to external networks.
Ownership: Often involves multiple organizations and service providers, with shared responsibilities for management.
Connection Type: Uses a variety of technologies, including leased lines, satellite links, and the internet, to connect different LANs over long distances.
Reliability: More prone to disruptions due to the wide area it covers, which may include various environmental and technical challenges.

M1: Network Infrastructure

Network infrastructure refers to the physical and virtual resources that enable network connectivity and communication. It includes all the equipment and software needed to send data, link devices, and keep the network running smoothly.

Software

  • Network Operating Systems (NOS): Software that manages network resources, controls access, and facilitates communication between devices.
  • Network Management Software: Tools used to monitor, manage, and troubleshoot the network to ensure optimal performance and security.

Hardware

  • Routers: Devices that connect different networks and guide data to the right places.
  • Switches: Devices that connect multiple devices within a LAN, allowing them to communicate with each other.
  • Cables: Physical connections like Ethernet cables that link devices together within the network.
  • Servers: Powerful computers that provide resources, services, or data to other computers (clients) over a network.
  • Firewalls: Security devices that monitor and control incoming and outgoing network traffic based on predetermined security rules.

Network Protocols

Network protocols are rules that determine how data is transmitted and received over a network, ensuring that devices can communicate effectively with each other. Examples include TCP/IP, HTTP, and FTP.

Services

  • DNS (Domain Name System): Translates human-readable domain names into IP addresses that computers can understand.
  • DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses to devices on the network, making it easier to connect new devices.

M1: Peer-to-Peer Network Architecture

Architecture: All computers are connected and have equal roles.
Privileges: Each computer shares data processing responsibilities equally.
Ideal For: Small networks with up to 10 computers.
Server Role: No central server is involved.
Permissions: Each computer has assigned special permissions.
Issue: Problems arise if a computer with a resource fails or malfunctions.

Advantages:

  • Less costly since there is no dedicated server.
  • Easy to set up and manage due to the small network size.
  • Highly reliable as the failure of one machine does not affect the functionality of others.

Disadvantages:

  • Lack of centralized systems makes data backup difficult.
  • No managed security – each computer handles its own security.

M1: Client-Server Network Architecture

Architecture: Client computers rely on a central server for resources and security.
Server Role: Manages network resources and security.
Communication: Clients communicate through the server.
Data Transfer: Clients must request permission from the server to send data to another client.
Advantages:

  • Data backup is achievable with the presence of a centralized system.
  • A dedicated server improves overall performance through proper organization and management of network resources.
  • Enhanced security enforcement as the central computer administers all shared resources.
  • Faster resource sharing due to orderly request handling.

Disadvantages:

  • Dedicated servers are expensive, making the network costly.
  • Network administration requires skilled personnel.

M1: Network Speeds

Bandwidth: The maximum rate at which data can be transferred over a network connection, usually measured in bits per second (bps). Common units are kilobits per second (Kbps), megabits per second (Mbps), and gigabits per second (Gbps).
Latency: The time it takes for data to travel from the source to the destination, often measured in milliseconds (ms). Lower latency means faster communication.
Throughput: The actual rate of data transfer achieved over a network, which can be affected by network congestion, hardware limitations, and other factors.
Download Speed: The rate at which data is transferred from the network to a user’s device.
Upload Speed: The rate at which data is transferred from a user’s device to the network.

Connection Types

  • Ethernet
  • Wi-Fi
  • Fiber Optic
  • DSL/Cable

M1: IP Address Classes

IP addresses are categorized into different classes based on their range, each designed for specific network sizes and purposes. The default IP address classes are:

Class A

Range: 1.0.0.0 to 126.0.0.0
Default Subnet Mask: 255.0.0.0
Purpose: Used for large networks with many devices (up to 16 million hosts).
Leading Bit: Starts with a 0.

Class B

Range: 128.0.0.0 to 191.255.0.0
Default Subnet Mask: 255.255.0.0
Purpose: Designed for medium-sized networks (up to 65,000 hosts).
Leading Bit: Starts with 10.

Class C

Range: 192.0.0.0 to 223.255.255.0
Default Subnet Mask: 255.255.255.0
Purpose: Suitable for small networks (up to 254 hosts).
Leading Bit: Starts with 110.

Class D

Range: 224.0.0.0 to 239.255.255.255
Purpose: Reserved for multicast groups (not used for typical host communication).
Leading Bit: Starts with 1110.

Class E

Range: 240.0.0.0 to 255.255.255.255
Purpose: Reserved for experimental use (not available for public use).
Leading Bit: Starts with 1111.

Each class serves a specific role in network design and IP address allocation, with Class A for the largest networks and Class C for smaller networks. Classes D and E are for special uses like multicasting and experimentation.

M1: The 7 Layers of the OSI Model

The OSI Model is a conceptual framework that standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. It has seven layers:

Physical Layer

Manages the physical connection between devices. It handles the transmission of raw binary data (0s and 1s) over physical media like cables or wireless signals.

Data Link Layer

Ensures reliable data transfer between devices on the same network. It organizes data into frames, detects errors, and handles error correction.

Network Layer

Routes data packets between different networks. It handles logical addressing (e.g., IP addresses) and determines the best path for data to travel from source to destination.

Transport Layer

Manages end-to-end communication and ensures complete and correct data transfer. It handles error recovery, flow control, and data segmentation (using protocols like TCP and UDP).

Session Layer

Manages and controls sessions between applications. It establishes, maintains, and terminates connections or sessions between communicating applications.

Presentation Layer

Translates data formats and handles data encryption and compression. It ensures that data is presented in a format that the application layer can understand.

Application Layer

Provides network services directly to end-user applications. It interacts with software applications to support functions like file transfers, email, and web browsing.

Each layer has specific functions that contribute to the overall process of network communication, ensuring data is transmitted effectively from one application to another.

M1: Network Administrator

A network administrator ensures a network runs smoothly and efficiently. Their key tasks include:

  1. Managing Storage: Handling physical and cloud storage.
  2. Testing and Security: Conducting basic tests and enforcing security.
  3. Supporting Design: Assisting with network design and models.
  4. System Management: Managing operating systems and servers.
  5. Updating Software: Installing and updating software.
  6. Troubleshooting: Diagnosing and fixing network problems.
  7. Repair and Upgrade: Performing repairs and network upgrades.
  8. Configuring Devices: Setting up network devices like switches, routers, and servers.

A network administrator needs strong IT and networking skills, critical thinking, and analytical abilities.

Collisions and Broadcast Domains

Collisions and broadcast domains are important concepts in network management:

Collisions

Definition: Occur when two or more devices try to send data over the same network channel simultaneously, causing their data packets to interfere with each other.
Impact: Can lead to data loss and reduced network performance.
Mitigation: Technologies like CSMA/CD (Carrier Sense Multiple Access with Collision Detection) are used to manage and reduce collisions in Ethernet networks.

Broadcast Domains

Definition: A broadcast domain is a network segment where a broadcast message sent by any device is received by all devices within that segment.
Scope: All devices within a broadcast domain can receive broadcast messages. Routers and VLANs (Virtual Local Area Networks) are used to segment broadcast domains and limit the reach of broadcast traffic.
Purpose: Helps manage and contain broadcast traffic, improving network performance and reducing unnecessary load on devices.