Computer Networking and Architecture Fundamentals

Posted on Jul 22, 2026 in Computers

Data Transmission and Networking

What is a packet?

A packet is a small unit of data sent across a network. Large files are divided into packets so they can be transmitted more efficiently.

What is a header?

A header is part of a packet. It contains the destination address and sequencing information so the packet reaches the correct device.

What is a payload?

A payload is the part of a packet that contains the actual data being sent.

What is a trailer?

A trailer is the last part of a packet. It contains information used for error checking.

What is packet switching?

Packet switching is a method of sending data where packets can travel through different routes before reaching the destination. The receiving device reassembles them into the correct order.

What is a router?

A router is a network device that forwards data packets to the correct destination. It connects networks and allows devices to communicate.

Transmission Methods

  • Serial transmission: Sends one bit at a time through a single communication channel. It is reliable for long-distance communication.
  • Parallel transmission: Sends several bits at the same time through multiple communication channels. It is faster over short distances.

Communication Directions

  • Simplex: Data travels in one direction only (e.g., keyboard to computer).
  • Half-duplex: Data travels in both directions, but not at the same time (e.g., walkie-talkie).
  • Full-duplex: Data travels in both directions at the same time (e.g., telephone call).

Error Detection and Control

  • Parity check: Adds an extra bit to the data to detect errors.
  • Checksum: Calculates a value from the data; the receiver compares this value to detect errors.
  • Echo check: The receiver sends the data back to the sender to compare with the original.
  • ARQ (Automatic Repeat reQuest): If an error is detected or no reply is received, the data is sent again.

Encryption Basics

  • Encryption: Converts readable data into unreadable data to protect information.
  • Plaintext: The original readable data.
  • Ciphertext: The unreadable encrypted version.
  • Symmetric encryption: Uses the same secret key to encrypt and decrypt data.
  • Asymmetric encryption: Uses two keys: a public key for encryption and a private key for decryption.

Computer Architecture

Core Components

  • CPU (Central Processing Unit): The brain of the computer. It processes data, executes instructions, and controls the computer.
  • Microprocessor: A single integrated circuit that performs the functions of the CPU.
  • Embedded system: A computer built into another device to perform one specific task (e.g., washing machines, microwaves).

The CPU Cycle

  1. Fetch: The CPU retrieves the next instruction from memory.
  2. Decode: The CPU interprets the instruction.
  3. Execute: The CPU carries out the instruction.

Hardware and Memory

  • Input device: Hardware used to enter data (e.g., keyboard, mouse, microphone).
  • Output device: Hardware that presents information to the user (e.g., monitor, printer, speaker).
  • Sensor: An input device that detects physical changes in the environment (e.g., temperature sensors).
  • ADC (Analogue-to-Digital Converter): Converts analogue signals into digital data.
  • RAM (Random Access Memory): Temporary, volatile memory for active programs.
  • ROM (Read Only Memory): Permanent, non-volatile memory for start-up instructions.
  • Secondary storage: Permanent storage like HDDs, SSDs, and USB drives.
  • Virtual memory: Uses secondary storage as extra RAM when needed.
  • Cloud vs. Local storage: Cloud storage uses remote servers; local storage saves files directly on the device.

Network Infrastructure

  • Network: A group of connected devices sharing data and resources.
  • NIC (Network Interface Card): Hardware allowing a device to connect to a network.
  • MAC address: A unique hardware address for a network interface card.
  • IP address: A unique address used to identify a device on a network.
  • IPv4 vs. IPv6: IPv4 is a 32-bit addressing system; IPv6 is a 128-bit system providing more unique addresses.
  • DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses to devices.