Making the right choice between TCP vs. UDP protocols when designing or deploying a network service or application is essential in ensuring optimal performance.
Each of them supports data flow in computer networks and the internet. However, although the two protocols are in the same transport layer of the OSI model, they have some differences in how they connect and transmit data.
Usually, these differences make each more suitable and reliable for certain applications. As such, it is important to understand how each works, its benefits, limitations, and ideal applications.
Before we look at the differences, let us first learn some basics.
What is TCP?
The TCP (Transmission Control Protocol) is a connection-based protocol. Once a computer or device establishes a connection with another, such as a server, bidirectional data transfer will occur between the two. Once the data transfer is complete, the TCP will terminate the connection.
TCP has built-in error-checking features that monitor the transfer to ensure that the data received is the same as what was sent. The protocol is very reliable and suitable for transmitting data, still images, web pages, and more. Despite its reliability, the protocol has a higher overhead due to the feedback and other features that use more resources, such as bandwidth.
In a typical application, before it begins to transmit data between two devices, TCP must first establish a connection using a three-way handshake. The handshake process involves exchanging SYN (synchronize), SYN-ACK (synchronize-acknowledgment), and ACK (acknowledge) signals between the two devices. A successful handshake ensures a reliable connection but may consume additional resources and time.
TCP ensures that the connection is reliable and able to transmit data as required. As such, a TCP-based connection will always verify that the data packets sent from one end are received at the destination. For this reason, it is suitable for applications such as web browsing, file downloads, and others where quality and data integrity are essential.
What is UDP?
UDP (User Datagram Protocol) is a connectionless protocol that does not require error checking and recovery features. This is a simpler protocol with very low overheads since it does not need to open, maintain, and terminate a connection.
Usually, when using UDP, the device will send data to the recipient continuously regardless of whether it is received or not. For this reason, the protocol may not be suitable for applications such as viewing web pages, sending emails, downloading files, etc. The protocol is ideal for applications that require real-time communications, such as multitask network transmissions, broadcasts, etc.
Differences between TCP and UDP
As the communication technologies continue to evolve and become more widespread, most users may not differentiate between the TCP vs. UDP features, capabilities, and functions as well as the benefits and limitations.
We have compiled a list of differences as well as the applications that each support.
TCP vs. UDP features
| Characteristic/feature | TCP (Transmission Control Protocol) | UDP (User Datagram Protocol) |
| Connection | Connection-based: establishes a connection that it maintains when transmitting data. It then terminates the connection after completing the transmission. | Connectionless: does not establish a connection between the communicating devices. It thus does not need to establish, maintain or terminate. |
| Data Sequence | Transmits data in an orderly manner | Transmits data randomly |
| Data packet delivery | Ensures correct data is delivered to the destination | Does not check to confirm whether data reaches the destination or not. |
| Speed | Slower due to various overheads. It is also bulkier and inefficient. | Faster since it does not have overheads. It is also simpler and more efficient. |
| Error checking and data integrity | Performs thorough error and data integrity checks | Does not perform error checking or data integrity checks |
| Lost data packets | Retransmits lost or corrupted data packets | It does not retransmit since it does not even check. |
| Handshake | Uses three-way handshake – SYN, SYN-ACK, ACK | Does not use a handshake |
| Bandwidth use | Inefficient due to many overheads | Efficient, has fewer overheads |
| Weight | Heavyweight since it requires space and resources for setting up and maintaining the connection and flow control | Lightweight |
| Security | Only transfers data after confirming that it is connected to the correct server or client, hence more secure. | Transfers data without confirming the destination or getting a response, hence more vulnerable to security threats. |
| Broadcasting | Does not support broadcast applications | Supports broadcast and multicast |
| Ideal applications | HTTP, HTTPS, FTP, SMTP, POP, web browsing, file downloads, and more | Video games, streaming videos, DNS queries, video conferencing, VOIP, and more |
Use Cases for TCP
TCP is ideal for applications that require reliable data transmission regardless of the speed. It ensures that all sent packets reach the destination without any changes or corruption. However, ensuring the data integrity results in some overheads and delays when on poor networks. As such, TCP is suitable if you are looking for quality and do not mind the speed.
Typical applications for TCP include browsing a website, emails, transferring or downloading files, still images, etc.
TCP is used where data integrity is essential. For example loss of a few data packets in an email is unacceptable.
Use Cases for UDP
On the other hand, if you are interested in speed and not too much data quality, UDP is the ideal protocol. Since it is connectionless and does not check data integrity, the lightweight protocol has very low overheads and is much faster. Generally, UDP is suitable for applications such as VoIP, video chats, online gaming, streaming video, and others where the loss of packets will only have an insignificant impact.
Applications such as streaming video, VOIP, and others require a proper balance between data integrity and speed.
Although TCP has better control and ensures data integrity, determining and retransmitting the lost packets is inefficient and slow for applications such as real-time video communications.
On the other hand, UDP does not perform error detection and correction. As such, it is suitable for reliable and unreliable connections where replies may or may not come back to the sending machine. Also, since UDP does not require acknowledging and error detection, it supports an uninterrupted and continuous flow of packets hence much faster delivery than TCP. As such, UDP is more suited for video conferencing and similar applications where error checking and other controls may disrupt the flow.
Conclusion
Generally, TCP and UDP determine how two devices exchange data over a network. Although both rely on the Internet Protocol (IP), the data delivery method differs in terms of the connection, data integrity, transmission speed, and applications they support.
TCP is connection-oriented, while the UDP is connectionless. Since the UDP does not have higher overheads, it is much faster than the TCP, which utilizes some resources to open, maintain and terminate a connection. Additionally, TCP delivers data sequentially from the client to the server and vice versa. It arranges the data packets so that they are received in the correct order. This is a useful feature, especially when transmitting still images, browsing a website page, etc.
UDP does not guarantee an end to end communication. It also does not check to confirm if the receiver is ready or not, and these are some of the reasons it has fewer overheads. Since it requires less space and resources, UDP is usually simpler, faster, and more efficient. However, unlike the TCP, UDP does not retransmit the lost data packets, which may result in poor quality data.
