Computer Networking


A network is a collection of computers, servers, and other network devices connected to one another to communicate, share data and resources. Computer Networking facilitates communication and resource sharing between connected devices.


  • Nodes: Devices like computers, printers, or servers.
  • Links: Connection medium like cables or wireless signals.

Protocols: Rules and conventions governing how data is transmitted and received in a network.

  • TCP/IP (Transmission Control Protocol/Internet Protocol): The foundation protocol suite for the Internet. It provides end-to-end communication specifying how data should be packetized, addressed, transmitted, routed, and received.
  • HTTP (Hypertext Transfer Protocol): Used for transmitting web pages on the Internet. It defines how messages are formatted and transmitted and how web servers and browsers should respond to various commands.
  • HTTPS (Hypertext Transfer Protocol Secure): Secure version of HTTP, encrypting data transferred between the client and server using SSL/TLS.
  • FTP (File Transfer Protocol): Used for transferring files between a client and server on a computer network.
  • SFTP (Secure File Transfer Protocol): A secure version of FTP that uses SSH to encrypt data.
  • SMTP (Simple Mail Transfer Protocol): Used for sending emails from a client to a server or between servers.
  • POP3 (Post Office Protocol version 3): Protocol used by email clients to retrieve emails from a server.
  • IMAP (Internet Message Access Protocol): Allows an email client to access emails stored on a remote server.
  • DHCP (Dynamic Host Configuration Protocol): Assigns IP addresses dynamically to devices on a network, simplifying network administration.
  • SSL/TLS (Secure Sockets Layer/Transport Layer Security): Protocols used to secure communication over a computer network, commonly used in HTTPS for web browsing, FTPS for file transfers, and SMTPS for email.
  • ARP (Address Resolution Protocol): Maps IP addresses to MAC addresses in a local network.
  • RTP (Real-time Transport Protocol): Used for delivering audio and video over IP networks.
  • RDP (Remote Desktop Protocol): Allows users to remotely connect to and control another computer over a network.
  • (VoIP) Voice over Internet Protocol (VoIP), is a technology that allows you to make voice calls using a broadband Internet connection instead of a regular (or analog) phone line.


Local Area Network (LAN):

     – Covers a small geographical area like a home, office, or campus.

     – High data transfer rates.

Wide Area Network (WAN):

     – Spans large distances, connecting LANs across cities, countries, or continents.

     – Slower data transfer rates compared to LAN.

Metropolitan Area Network (MAN):

     – Covers a city or a large campus.

     – Faster than WAN but slower than LAN.

Personal Area Network (PAN):

     – Connects devices within a person’s workspace.

     – E.g., Bluetooth devices, Infrared, USB connections.


Refers to the physical or logical arrangement or structure of nodes (such as computers, routers, switches and other devices and connections to form a network. In simple terms, a topology is like a blueprint of a network that outlines the layout and structure of a network. It shows how devices are connected and how data is transmitted between devices on a network. The arrangement influences how efficient, reliable and scalable of the network. By understanding network topology, Network Administrators and Engineers can easily plan, manage and troubleshoot a network effectively.

Before a Network Engineer decides to setup a network topology, the following needs to be considered:

Needs Assessment:

  • Identify the organization’s network requirements, including the number of users, devices, and the types of applications and services that will be used.
  • Determine bandwidth requirements for data, voice, and video traffic.

Site Survey:

  • Conduct a physical site survey to assess the current network infrastructure or if there’s none, the available space for equipment, and potential challenges.
  • Identify existing cabling, power sources, and other infrastructure components. If it’s a new setup brainstorm how to go about setting up all these components.

Topology Selection:

  • Select and outline an appropriate network topology (e.g., star, bus, ring, mesh) based on the organization’s needs, scalability, and budget.
  • Determine the placement of network devices such as switches, routers, firewalls, and access points.


  • Develop a budget for the network infrastructure, considering hardware, software, and ongoing maintenance costs.

Hardware and Software Selection:

  • Choose the appropriate networking hardware (switches, routers, firewalls, etc.) and software (operating systems, network management tools).
  • Ensure compatibility and support for the selected network topology and protocols.

Security Considerations:

  • Develop a comprehensive security plan, including firewall configurations, intrusion detection/prevention systems, VPNs, and access control policies.
  • Consider physical security measures to protect networking equipment and data centers.

IP Addressing and Subnetting:

  • Plan IP addressing schemes and subnetting to efficiently allocate IP addresses to devices and manage network traffic.
  • Implement DHCP for dynamic IP address assignment if needed.

Redundancy and High Availability:

  • Design the network with redundancy to ensure high availability and fault tolerance.
  • Implement technologies like load balancing, and failover mechanisms.


  • Create detailed network documentation, including network diagrams, configuration files, IP address assignments, and device inventory.
  • Document network policies, procedures, and troubleshooting guidelines.

Testing and Validation:

  • Conduct thorough testing of the network infrastructure before deployment to identify and resolve any issues.
  • Validate network performance, reliability, and security configurations.

Training and Support:

  • Provide training for IT staff and end-users on the new network setup, protocols, and security practices.
  • Establish a support system for ongoing network monitoring, maintenance, and troubleshooting.


There are various types of Network Topology, and each of them have their features, advantages and limitations. An organisation chooses a topology based on their requirements and size.

Bus Topology: All devices share a single communication line.

Star Topology: All devices are connected to a central hub or switch.

Ring Topology: Devices form a closed loop; each device connects to two other devices.

Mesh Topology: Devices are interconnected, providing redundant paths.

Hybrid Topology: Combination of two or more topology.


Definition: Physical pathways through which data is transmitted between nodes.


Twisted Pair: Consists of pairs of insulated copper wires twisted together.

Coaxial Cable: Central conductor surrounded by an insulating layer and a shielding layer.

Fiber Optic Cable: Uses light signals transmitted through glass or plastic fibers.

Wireless Media: Radio waves, microwaves, or infrared signals for wireless communication.


Setting up and arranging network devices and services to enable communication.


  • IP address assignment.
  • Setting up routers, switches, and access points.
  • Configuring security settings.
  • Establishing network protocols and services.


Transmission of digital data between two or more devices.


  • Packet Switching: Data is divided into packets for transmission, reassembled at the destination.
  • Circuit Switching: Dedicated communication path established for the duration of the connection.
  • Protocols: TCP/IP, HTTP, FTP, SMTP, etc., facilitate data transmission over networks.


Measures to protect data from unauthorized access, alteration, or destruction.


  • Firewalls: Monitor and filter incoming and outgoing network traffic.
  • Encryption: Converts data into a coded form to prevent unauthorized access.
  • Access Control: Restricts user access to network resources based on permissions.


  • Data breaches, malware attacks, insider threats, etc.
  • Regular updates and monitoring are essential for maintaining network security.


Peer-to-Peer (P2P) Network:

In a P2P network, each device, called a peer, has equivalent capabilities and responsibilities. Peers can act as both clients and servers to other peers on the network.

  • Resource Sharing: Resources like files, printers, or bandwidth are shared directly between peers without the need for a centralized server.
  • Decentralized: No centralized authority or server is required to control the network. Peers communicate directly with each other.
  • Scalability: Generally suitable for small networks with a limited number of devices and users due to the decentralized nature.

Examples of P2P: BitTorrent for file sharing, Skype for peer-to-peer communication.

Client/Server Network:

In a Client/Server network, resources and services are centralized and managed by a dedicated server. Clients request services or resources from the server, which then provides the requested service.

  • Resource Sharing: Resources are stored and managed centrally on the server. Clients access these resources by requesting them from the server.
  • Centralized Control: A server(s) controls the network, managing access to resources, user permissions, and data storage.
  • Scalability: Generally suitable for larger networks with a large number of devices and users as it can handle complex operations more efficiently than P2P networks.

Examples: Web servers hosting websites, Email servers handling email services, Database servers managing data storage and retrieval.

Key Differences:

  • Control:
    • P2P: Decentralized, no central control.
    • Client/Server: Centralized control with a dedicated server managing resources.
  • Resource Sharing:
    • P2P: Direct sharing between peers without a central server.
    • Client/Server: Resources are stored and managed centrally on a server, accessed by clients.
  • Scalability:
    • P2P: Generally suitable for small-scale networks.
    • Client/Server: More suitable for large-scale networks due to centralized management and control.
  • Performance:
    • P2P: Performance can vary based on the number of peers and network conditions.
    • Client/Server: Generally, offers better performance and reliability for larger networks with high traffic loads.


Here’s a list of common types of servers used in networking and computing environments:

  1. Web Server:
    • Responsible for hosting websites and web applications.
    • Examples: Apache HTTP Server, Nginx, Microsoft IIS (Internet Information Services).
  2. File Server:
    • Stores and manages files accessible to clients over a network.
    • Facilitates file sharing and centralized data storage.
  3. Database Server:
    • Manages databases and provides database services to other computers in the network.
    • Examples: MySQL, Oracle Database, Microsoft SQL Server.
  4. Application Server:
    • Handles the execution of applications and provides services like transaction management, messaging, and data mapping.
    • Supports the development and deployment of custom applications.
  5. Mail Server:
    • Manages and transfers emails between users within a network or across networks.
    • Examples: Microsoft Exchange Server, Postfix, Sendmail.
  6. Proxy Server:
    • Acts as an intermediary between clients and other servers to provide services like web content caching, filtering, and improved performance.
  7. DNS Server (Domain Name System):
    • Translates domain names to IP addresses and vice versa, facilitating domain name resolution.
    • Examples: BIND, Microsoft DNS Server, Google Public DNS.
  8. DHCP Server (Dynamic Host Configuration Protocol):
    • Assigns IP addresses dynamically to devices on a network, simplifying network configuration and management.
    • Examples: ISC DHCP, Microsoft DHCP Server.
  9. Print Server:
    • Manages printers and print jobs, allowing users to send print requests to network printers.
  10. VPN Server (Virtual Private Network):
    • Provides secure remote access to a private network over the Internet.
    • Examples: OpenVPN, Cisco VPN, Microsoft VPN Server.
  11. Backup Server:
    • Manages backup and recovery operations, storing copies of data for disaster recovery and data protection.


Network models are conceptual frameworks that define the structure and operations of computer networks. These models provide a structured approach to understanding, designing, and implementing network architectures and protocols. They help in organizing and standardizing network functions, services, and communication processes, ensuring compatibility across different network technologies and devices. There are two types of Network models: OSI and TCP/IP

The TCP/IP model is more widely used and considered more modern than the OSI model in practical networking applications, especially in the context of the Internet and most private network implementations.

Open Systems Interconnection (OSI) Model

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand network interactions and communications between different networking systems. It consists of seven layers, each representing a specific function or set of functions in the networking process. The OSI model serves as a standard for network architecture and design, ensuring interoperability and compatibility between different network technologies and protocols.

Here’s a detailed explanation of each layer of the OSI model:

1. Physical Layer (Layer 1)

  • Function: This layer deals with the physical connection between devices and transmission of raw binary data over the physical medium.
  • Key Concepts:
    • Transmission media (cables, wireless signals).
    • Signal transmission (analog/digital).
    • Physical connectors and interfaces.
  • Devices: Network Interface Cards (NICs), Hubs, Repeaters.

2. Data Link Layer (Layer 2)

  • Function: Responsible for creating a reliable link between two directly connected nodes, providing error detection and correction.
  • Key Concepts:
    • Framing (encapsulation of data into frames).
    • MAC (Media Access Control) addressing.
    • Error detection and correction.
  • Devices: Switches, Bridges, NICs.

3. Network Layer (Layer 3)

  • Function: Handles the routing and forwarding of data packets between different networks.
  • Key Concepts:
    • Logical addressing (IP addressing).
    • Routing (determining the best path for data transmission).
    • Packet switching.
  • Devices: Routers, Layer 3 Switches.

4. Transport Layer (Layer 4)

  • Function: Ensures end-to-end communication by segmenting, managing, and reassembling data between the source and destination.
  • Key Concepts:
    • Segmentation/De-segmentation.
    • Flow control.
    • Error recovery.
  • Protocols: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

5. Session Layer (Layer 5)

  • Function: Manages and maintains sessions (connections) between applications running on different devices.
  • Key Concepts:
    • Session establishment, maintenance, and termination.
    • Synchronization.
  • Activities: Authentication, Authorization, Session checkpoints.

6. Presentation Layer (Layer 6)

  • Function: Translates, encrypts, or compresses data to ensure compatibility between different systems.
  • Key Concepts:
    • Data encryption/decryption.
    • Data compression.
    • Data translation (e.g., ASCII to EBCDIC).
  • Activities: Data encryption, Data compression, Data translation.

7. Application Layer (Layer 7)

  • Function: Provides interface between the user application and the network services, allowing applications to access network resources.
  • Key Concepts:
    • Application services (e.g., HTTP, FTP, SMTP).
    • API (Application Programming Interface).
    • User interfaces.
  • Examples: Web browsers, Email clients, File transfer programs.

Transmission Control Protocol/Internet Protocol (TCP/IP) Model

TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of communication protocols used for interconnecting network devices on the Internet and private networks.

  • Standardization: Developed by the U.S. Department of Defense (DoD) in the 1970s as a robust protocol suite for military and academic use.
  • Foundation: The basis for the Internet and most modern network communication.

TCP/IP Model Layers: The TCP/IP model consists of four (4) layers:

  • Network Access Layer
  • Internet Layer
  • Transport Layer
  • Application Layer

Network Access Layer (Layer 1)

  • Function: Handles physical connections and data transmission over the physical medium.
  • Key Concepts:
    • Media types and technologies.
    • Physical addressing.
    • Frame creation and transmission.
  • Protocols: Ethernet, Wi-Fi, PPP (Point-to-Point Protocol), DSL (Digital Subscriber Line), ISDN (Integrated Services Digital Network).

Internet Layer (Layer 2)

  • Function: Responsible for packet forwarding, routing, and addressing.
  • Key Concepts:
    • IP addressing.
    • Packet routing.
    • ICMP for error reporting.
  • Protocols: IP (Internet Protocol), ICMP (Internet Control Message Protocol), ARP (Address Resolution Protocol).

Transport Layer (Layer 3)

  • Function: Ensures end-to-end communication by segmenting, managing, and reassembling data between the source and destination.
  • Key Concepts:
    • Segmentation/De-segmentation.
    • Flow control.
    • Error recovery.
  • Protocols: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

Application Layer (Layer 4)

  • Function: Provides applications with access to network services and protocols.
  • Key Concepts:
    • Data representation and encryption.
    • Application communication protocols.
  • Protocols: HTTP, HTTPS, FTP, SMTP, DNS, SNMP, Telnet, SSH.

Key Features of TCP/IP Model:

  • Open Architecture: Publicly available and can be used by any organization or individual.
  • Modular Design: Each layer performs specific functions independently of the others, allowing for flexibility and scalability.
  • Interoperability: Ensures different devices and networks can communicate and exchange data.

Comparison with OSI Model:

  • Difference: TCP/IP model combines the presentation and session layers into the application layer, resulting in four layers instead of seven in the OSI model.
  • Simpler Structure: TCP/IP is considered more straightforward and is widely used in practical networking, whereas the OSI model is more theoretical.
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