TCP vs UDP

What is User Datagram Protocol (UDP)?

UDP stands for User Datagram Protocol. It is a connectionless communication protocol used for transmitting data without establishing a dedicated end-to-end connection. Unlike TCP, UDP does not ensure reliability, error correction, or in-order delivery of packets. Because it avoids the overhead of acknowledgments and retransmissions, UDP is much faster and more efficient, especially in time-sensitive applications.

How Does UDP Work?

UDP is a connectionless protocol, meaning it does not perform a handshake before sending data. Instead, it sends discrete packets (called datagrams) directly to the recipient without checking if they were received or in what order.

1. No Handshake: Data is sent without prior connection establishment.
2. No Acknowledgment: The sender does not wait for delivery confirmation.
3. No Sequencing or Retransmission: Packets may arrive out of order or be lost, and no corrective action is taken.
4. Fast and Lightweight: Minimal protocol overhead ensures low latency.
5. Best for Real-Time Use: Ideal where speed is more critical than reliability (e.g., video calls, online gaming).

Sandwich Analogy

• TCP is like hand-delivering a sandwich and ensuring the recipient gets it.
• UDP is like throwing a sandwich across the room—it’s faster but may not always arrive intact.

TCP vs UDP

• TCP = Reliable, slower, ordered
• UDP = Fast, unreliable, unordered

Features of UDP

• Connectionless Protocol: No setup or teardown of connections.
• Low Overhead: Lightweight due to no flow control or error checking.
• Supports Multicasting: Efficiently sends data to multiple recipients.
• Used in Real-Time Apps: Suits live audio/video or gaming.
• No Retransmission Logic: Doesn’t resend lost packets, ensuring speed.

Applications of UDP

• Online Gaming: Fast response is vital; some data loss is tolerable.
• Video and Audio Streaming: Reduces buffering for smooth playback.
• DNS Queries: Quick and efficient for simple request/response.
• VoIP and Video Calls: Delivers low-latency communication.
• Multicasting and Broadcasting: Sends data to many users simultaneously.
• TFTP (Trivial File Transfer Protocol): Uses UDP for simple, quick transfers.

UDP is preferred where low latency and speed are more valuable than 100% reliability.

Advantages of UDP

• Faster Data Transmission: No connection setup or acknowledgments.
• Low Latency: Ideal for real-time applications.
• Simple Protocol: Easy to implement and use.
• Supports Broadcast and Multicast: Efficient for group communication.
• No Congestion Control: Sends data continuously without delays.

Disadvantages of UDP

• Unreliable Delivery: No guarantees data will reach the destination.
• No Acknowledgment or Retransmission: Lost packets are not recovered.
• No Ordering: Packets may arrive out of sequence.
• No Flow Control: Can overwhelm the receiver with too much data.
• Susceptible to Data Loss: Especially in congested networks.

Where UDP is Used?

1. Gaming: Prioritizes fast action and real-time response.
2. Video Streaming: Smooth, continuous playback despite occasional loss.
3. Online Video Chats: Supports low-latency communication.
4. Both TCP and UDP are process-to-process protocols, but they serve different needs based on the application's tolerance for data loss and latency.

Real-Life Example to Understand TCP vs UDP Protocols

Consider a simple example to understand the fundamental difference between TCP & UDP protocols:

Assume two buildings, A and B. And there is a river between them. The goal is to send a letter from building A to building B. Now there are two ways to accomplish this
Method 1: Build a bridge over the river and deliver the letter.

Method 2: Use a pigeon to deliver the letter. 

Here, method 1 is TCP protocol where a connection is built(bridge in this example) between the two devices and then transmitted the data(letter).

Method 1 is reliable because we can directly reach the other end without any error in or loss of data.

Here method 2 is UDP as no connection is required to transmit the data(letter). UDP is faster than TCP, but it is not reliable. Because it is not guaranteed that the pigeon will go to the correct destination, the letter can be lost by the pigeon. 

Must Read Stop and Wait Protocol.

You can read related articles such as Congestion Control in Computer Networks here.

Comparison Between TCP and UDP

Also see, Difference Between Compiler and Interpreter and Assembler

Frequently Asked Questions

List all layers of the TCP/IP model?

There are seven layers in the OSI model. They are:
Physical layer
Data link layer
Network layer
Transport layer
Application layer

What is the Simplex mode?

The communication is unidirectional in Simplex mode. Only one of the devices on a link can be a sender, and the other can only receive.

What is Half-duplex and Full-duplex mode?

Both the devices can act as a sender or receiver in half-duplex mode. But at a time, only one device can transmit data over the link.
Full-duplex mode is bi-directional, i.e. both devices can send or receive data at the same time.

List most common network topologies?

Some of the most common network topologies are:
Mesh topology
Bus topology
Star topology
Ring topology

Conclusion

Cheers if you reached here!! 

In this article, we discussed that the both TCP and UDP are vital protocols in the Transport Layer, each serving distinct purposes. TCP ensures reliable, ordered, and error-free data transfer, making it ideal for tasks that require precision, such as file transfers and web browsing. In contrast, UDP offers faster, connectionless communication, making it suitable for real-time applications like gaming and video streaming, where speed is paramount and minor data loss is tolerable. The choice between TCP and UDP ultimately depends on the application's specific needs or task.

Recommended Readings:

• Introduction to computer networks
• Basic Characteristics of Computer Networks
• Types of Area Networks
• OSI Model
• TCP/ICP Model 
• OSI v/s TCP/IP Model
• Data Link Layer
• Physical Layer
• Network Layer
• Session Layer
• Presentation Layer
• Application Layer
• Routing and its types in Computer Networks
• TCP UDP sockets and Congestion Control
• Asynchronous Data Transfer