What Is the Difference Between UDP and TCP?

When setting up a router, configuring firewall software, or looking through VPN functions, you must have heard about TCP and UDP. But what is the distinction between them?

TCP and UDP are two protocols that decide how you exchange online data. They share many similarities, both of which are based on the IP protocol, but their differences make them suitable for different purposes. They are the two protocols that internet users interact with every day.

You might have seen terms such as OpenVPN over TCP or OpenVPN over UDP if you have ever gone through technical mumbo-jumbo while using a VPN. You may know that the most secure VPN protocol is OpenVPN. But what is up with TCP and UDP? What do these terms refer to?

Knowing their functions and uses helps you to understand the difference between TCP and UDP.

What Is a TCP?

TCP stands for Transmission Control Protocol. It is the protocol that is most used on the internet. Your processor sends TCP packets to the web server’s location when you load a web page, asking it to send the web sheet to you. The web server answers by sending a stream of TCP packets stitched together by your network browser to form and display a web page.

Your web browser sends TCP packages to the server, and the server sends TCP packets back when you connect a link, sign in, post a comment or do anything else. TCP is not just one-way communication that sends packets back to the remote system to recognize that your packages have been received.

It guarantees that the recipient will receive the packets in order by numbering the packets. The receiver sends messages back to the dispatcher, stating that the numbers have been received.

If the sender does not receive an accurate response, they will send the packets back to the recipients to ensure they get them. They also check the packages for mistakes as well.  This reliability is what TCP is all about.

When a packet is sent with TCP they also rack them so that there is no data loss or corruption in transit. Therefore, even though there are network hiccups, file downloads do not become corrupt.

What Is UDP?

UDP stands for User Datagram Protocol. The UDP protocol functions like the TCP, but it throws all the error-checking stuff out. All the back-and-forth correspondence and deliverability means that things slow down.

Packets are only sent to the receiver by using UDP. The sender will not wait to ensure that the receiver receives the package; it will immediately begin shipping the next packets. Too bad, you cannot ask for those packets again if you are the receiver and you lose any UDP packets. There is no guarantee that you can receive all the packages, and if you skip it, there is no means to ask for a package again; eliminating all these overhead means that computers will communicate faster.

When speed is required and error correction is unnecessary, UDP is used. UDP is often used for live broadcasts and online games, etc.

What Are the Key Differences Between UDP and TCP

There are some key differences to take note of between both packets. Here they are below:

1. Connection and connectionless

TCP is a protocol that is connection-driven, and UDP is a connectionless protocol. TCP establishes a relationship between a sender and a receiver until it is possible to send data. Before sending data, UDP does not create a link.

2. Sequencing

TCP is a secure protocol that adds to the data packets a sequence number when a stream is sent out. It helps the receiver to organize the message and stitch it back together.

UDP does not add a number to its header, meaning that the receiver has no way of knowing whether all the packets have been received and are in the correct order.

TCP does order and sequencing to ensure that packets sent from a server are delivered to the customer in the same order they sent them. The UDP sends packets in any order, on the other hand.

3. Reliability

TCP is dependable. It is guaranteed that data sent using a TCP protocol is transmitted to the receiver. If data is lost in transit, the data will be retrieved and sent back. TCP will also check error packets and monitor packets to avoid losing or corrupting data.

UDP is unreliable, offers no guaranteed delivery, and a datagram packet can become corrupt or lost in transit.

4. Header size

TCP packets’ header is larger than that of UDP packets because TCP has more information (packet sequence, error detection, acknowledgment field, etc.). It makes it heavy for each package. TCP connections are thus slower than UDP connections.

5. Detection/Correction of Errors

Error detection via checksum occurs in UDP, but there is no error correction. If you notice that a given packet is erroneous, you can discard it.

TCP has methods of error detection and correction. If a packet displays a notification that there is a corrupt parcel, TCP does not receive it. It prompts the sender to resend the package. This way, it delivers the full message without mistakes.

6. Acknowledgment

When the receiver receives TCP packets, it sends an acknowledgment back to the sender. When a  sender does not receive recognition, believe that the packages are not to be sent or have been compromised. The resending of the packets would then continue.

On the other hand, UDP does not give an acknowledgment, so the sender would not know whether the packets have been received or not.

7. Transfer method

TCP sends out a stream of data packets while UDP sends packets individually. There is no defined boundary for the data stream, but individual packages have appropriate boundaries.

8. Congestion Control

TCP uses a method for flow control to ensure that a sender does not overload a recipient by transmitting too many packets at once. In a send buffer, the TCP stores data and receives data in a receive buffer.

When an application is ready, data from the receiving buffer will be read. The receiver would not handle further data and would drop it if the receive buffer is full.

The UDP does not support flow control. Packets arrive in a continuous stream of UDP.

9. Application

TCP is better suited for use for applications requiring high reliability where timing is less of a concern.

  • World Wide Web (HTTP, HTTPS)
  • Safe Shell (SSH)
  • Protocol for File Transfer (PFT)
  • Email (SMTP, POP/IMAP)

For applications that require speed and performance, UDP is best suited.

  • VPN tunneling facility
  • Video streaming
  • Computer games
  • Live broadcasts
  • Domain Name System (DNS)
  • Voice over Internet Protocol (VoIP)
  • Trivial File Transfer Protocol (TFTP)

The graph below summarizes the differences in the details above.

ConnectionLink-orientedConnectionless connection
Header SizeDue to overheads, header size packets are massiveLightweight packets with limited headers
Error Detection/correctionChecking for errors and error recoveryThey check for errors but no recovery. They discard corrupted packets and never ask for them again
AcknowledgmentReceiver sends acknowledgmentReceiver doesn’t send acknowledgment
Transfer MethodStreamIndividual packets
Regulation of CongestionYesNo
ApplicationsTransfer of data, email, web browsingGaming, broadcasting, video conferencing

Features of the TCP

Here are a few features of the TCP to help with identification:

1. Multiplexing and Addressing

You use TCP ports to handle different network processes for upper-layer applications. It often multiplexes the data obtained by various procedures and then broadcasts the data packet combined with the network access layer.

2. To build, maintain and terminate links

Several sets of procedures and rules are followed in this protocol to establish a connection between the source and the destination’s end. Handshake protocols & procedures exist and are used to preserve and understand the ongoing process of communication.

In the end, specific rules are often followed to terminate the connection until the contact between the end of the source and the destination is over.

3. Data Packaging

Until it transmits data packets to a higher layer for communication, the TCP first sets out the process for sharing the data in message format and then delivers it to the destination.

The receiver decodes and unpacks the data at the destination end and forwards it to the upper layer applications.

Features of the UDP

Here are a few features of the UDP:

1. Data transfer from the higher layer

The UDP procedure receives the data to be transmitted from the higher layer, converts it to UDP messages, and then transfers it to the UDP communication program.

2. UDP message encapsulation

The data field encapsulates the UDP message. The UDP header consists of the source port and endpoint port domains and works out the checksum’s importance.

3. The message passed to the Next Layer

After you compute the above fields, the UDP will forward the message for communication to the IP. The phase will be reversed at the end of the goal.


Both TCP and UDP are protocols that are used over the Internet to transfer bits of data, called packets. Both of them are built on the Internet protocol. In other words, the packet is sent to an IP address, whether you are sending a packet via TCP or UDP. These packets are handled equally when they are routed to the intermediate routers and then to the destination from your device.