Data Packets | Computer for GCSE/IGCSE - Year 11 PDF Download

What are packets?

• Information on the internet is broken down into packets which are created by TCP and transmitted over the internet.
• Packets are small pieces of information or data. TCP, short for Transmission Control Protocol, is responsible for organizing data transmission across networks.
• Breaking data into small chunks facilitates easier and quicker routing over the internet compared to large data chunks.
• Routing involves determining the most efficient path across a network. Data transmitted can range from text, images, audio, video, animations, or a mix of these elements.
• Routing: Routing is the process of determining the most efficient path on a network for data to travel.
• Data Transmission: Data can encompass a variety of forms such as text, images, audio, video, and animations, either individually or in combination.

What is the Content of Packets?

• Packets Overview: Packets serve as discrete units of data, each containing a payload, which is the actual information being transmitted.
• Packet Structure: Each packet imitates a postal letter, featuring key components:
  • Delivery Address: Represents the destination IP address where the packet is intended to go.
  • Return Address: Denotes the source IP address, serving as the return path for the packet.
  • Message: Contains the data payload, which is the main content of the packet.
• Packet Components: Packets are divided into three main sections:
  • Header: Includes crucial information such as the source IP, destination IP, packet number, and error checking data like checksum or parity bit.
  • Payload: Comprises the actual data being transmitted.
  • Trailer: Serves as the ending part of the packet.
  • The header contains:
    • Source IP: The Source IP address indicates the origin of the packet within the network.
    • Destination IP: The Destination IP address shows where the packet should be delivered.
    • Packet number: Packet number specifies the sequence of the packet in relation to the data transmission.
    • Error checker: Error checking mechanisms like checksums ensure data integrity during transmission.
• The trailer includes:
  • Additional error checks help in verifying data accuracy and completeness.
  • End of packet notification: End of packet notification signals the conclusion of a packet's transmission.

Packet Structure Overview

• Each packet typically includes a source IP address, destination IP address, payload (data), and a packet number.
• The structure of individual packets can vary based on the specific protocol used to create them, leading to different variations.

Error Checking Mechanisms

• Error checking protocols are crucial to ensure minimal to no corruption of data during packet transmission.
• Corruption in a packet can occur when data is altered, lost, or when unauthorized data is added to the packet.
• A parity bit is used to verify that bits have not been inadvertently altered during transmission.
• Checksums are calculated and compared to detect any discrepancies, indicating data corruption if values differ.

How are packets sent across the internet?

• Sending data packets over the internet is known as packet switching, which is a more efficient method compared to circuit switching.
• Packet switching involves:
  • Routers determine the most efficient path to send data packets towards their destination, akin to how drivers navigate traffic.
  • When congestion occurs on the internet, routers reroute packets to less congested paths, ensuring timely delivery.
  • Data packets from a single message can travel diverse routes before reaching the receiver, potentially arriving out of sequence. The recipient's system reorganizes these packets based on unique identifiers.
  • Files are segmented into packets, transmitted via various pathways using routers, and reassembled upon reaching the intended recipient.
  • Packet numbers play a crucial role in reconstructing the original message accurately, acting like pieces of a puzzle that fit together in the correct order.
  • Routers are equipped with routing tables that function as guides, akin to maps or contact lists, to efficiently direct packet traffic.
  • If a packet fails to reach its destination, the recipient can request a resend, prompting the sender to retransmit the missing packet.

Packet Switching Advantages

• Packet switching offers minimal interference and corruption since individual packets can be resent if lost or damaged. For example, imagine sending a large file over the internet. If a packet is lost or corrupted during transmission, only that specific packet needs to be resent, not the entire file. This saves time and bandwidth.
• Unlike traditional methods, with packet switching, the entire file doesn't require retransmission in case of corruption. Only the affected packets are retransmitted. This efficient process contributes significantly to saving time and internet resources.
• Packet switching enhances speed by breaking down data into smaller packets. Each packet independently navigates the network to find the quickest route to its destination. Consequently, the overall communication process is expedited compared to sending a large packet.
• Security is bolstered in packet switching due to the segmented nature of data transmission. Since data is divided into packets, each containing minimal information, it becomes more challenging for malicious entities to intercept and manipulate the entire data stream. This individual packet approach enhances data privacy and network security.