What’s the Difference Between TCP and UDP?

TCP (Transmission Control Protocol):

Imagine sending a package to a friend by mail. With TCP, it’s like sending a package with a tracking number and requiring your friend to acknowledge receiving it. If a part of the package is missing or damaged during delivery, you’ll send the missing parts again until your friend has everything correctly.

Key points:

  • Reliable: Ensures all the data gets to its destination and in the right order, like tracking a package.
  • Ordered: Data arrives in the order it was sent, like arranging items in a package in a specific order.
  • Slower: Takes a bit more time to make sure everything is delivered correctly.

Where is TCP used?

  1. Web Browsing:
    • HTTP (Hypertext Transfer Protocol): When you browse websites, your browser uses TCP to request and receive web pages, ensuring that all the data (like text, images, videos) arrives correctly and in order.
  2. Email:
    • SMTP (Simple Mail Transfer Protocol): Sending and receiving emails rely on TCP to ensure that email messages are reliably transmitted from the sender’s email server to the recipient’s email server.
  3. File Transfer:
    • FTP (File Transfer Protocol): TCP is used for FTP, a standard network protocol for transferring files from one host to another over a network.
  4. Remote Desktop Access:
    • RDP (Remote Desktop Protocol): TCP is used for remote desktop access, allowing users to control and work on a remote computer as if they were physically present at that machine.
  5. Secure Communication:
    • HTTPS (HTTP Secure): TCP is used for HTTPS, the secure version of HTTP, ensuring encrypted and secure communication for online transactions, login forms, and sensitive data exchange.
  6. Database Access:
    • Database Connections: TCP is often used for connecting to databases like MySQL, PostgreSQL, or SQL Server, allowing applications to send queries and receive responses reliably.
  7. Software Updates:
    • Downloading Updates: When you download software updates, TCP is used to ensure that all parts of the update are delivered accurately to your device.
  8. Messaging Applications:
    • Instant Messaging: TCP is used in applications like WhatsApp, Slack, or Facebook Messenger to ensure that messages are sent and received in the correct order and without loss.
  9. Online Shopping and Transactions:
    • eCommerce Transactions: When making purchases online, TCP ensures that the transaction data is transmitted reliably, avoiding errors or loss during the process.

In these examples, TCP’s strengths, such as reliable data delivery, in-order arrival of packets, and error checking, are crucial to ensure a seamless and accurate transfer of data for the respective applications and services.

UDP (User Datagram Protocol):

Now, think of sending a postcard to your friend. You send multiple postcards, but you don’t track them, and you don’t ask your friend to confirm receiving each one. Some might get lost, duplicated, or arrive out of order, but they’re quick to send.

Key points:

  • Unreliable: Doesn’t guarantee that all the data will get there, similar to sending postcards that might not always arrive.
  • Unordered: Data might arrive in a different order than it was sent.
  • Faster: Quick and efficient, but you may lose some postcards (data).

Where is UDP used?

  1. Real-Time Communication:
    • Voice Over IP (VoIP): Applications like Skype, Zoom, and online gaming use UDP for real-time voice communication because low latency is more important than guaranteed delivery of every packet.
    • Video Streaming: Streaming services like Prime, Netflix, HBO, YouTube, Twitch, and live broadcasting (to name a few) often use UDP to deliver video content efficiently, allowing for faster streaming with some tolerance for lost or out-of-order packets.
  2. Online Gaming:
    • Online Gaming Servers: Multiplayer online games use UDP for real-time game data transmission, such as player movements, actions, and interactions, where low latency and quick updates are crucial for a good gaming experience.
  3. DNS (Domain Name System):
    • DNS Queries: When a device needs to look up a domain name to get its corresponding IP address, it typically uses UDP for DNS queries, as it’s faster for small and quick transactions.
  4. Network Monitoring and Diagnostics:
    • Network Monitoring Tools: UDP is used in tools like SNMP (Simple Network Management Protocol) for network monitoring, where getting real-time data and statistics is essential, even if occasional data loss occurs.
  5. IoT (Internet of Things) and Embedded Systems:
    • IoT Devices: IoT devices often use UDP for transmitting sensor data or status updates to a central server due to its low overhead and speed, making it suitable for lightweight communication.
  6. Streaming Media and Broadcasting:
    • Internet Radio and TV: Broadcasting audio or video feeds over the internet, especially for live events or radio stations, frequently uses UDP for efficient streaming and real-time delivery.
  7. DHCP (Dynamic Host Configuration Protocol):
    • DHCP Requests: DHCP uses UDP for devices to request and obtain IP addresses and other network configuration parameters when they connect to a network.

In these scenarios, the advantages of UDP, such as low overhead, speed, and simplicity, outweigh the need for guaranteed delivery and ordered transmission of data.

In summary, TCP is like sending a package with tracking and ensuring everything arrives in order and complete, even if it takes a bit longer. UDP is like sending postcards quickly without tracking, and you’re okay if a few postcards don’t make it.

Credit: Cover image by Freepik