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Transmission Control Protocol vs User Datagram Protocol

TCP vs UDP

Networking, ultimately, is about the communication between computerized devices. Thinking in such simple terms can help you nail design and philosophy elements when you run your own network, and that can translate to faster speeds and better reliability and security.

So, how do computers talk?

They use a protocol, and in the modern world, two protocols come up a lot: TCP and UDP. Let’s take a closer look at each protocol and see what we can learn.

TCP - Transmission Control Protocol

Transmission control protocol (TCP) is a common option used to send information directly from one device to another. Many internet communication procedures and applications run on TCP.

At a basic level, TCP works by first establishing a handshake between the communicating devices. This means the devices go through a security protocol and create a secure connection. Because this happens before any packets are sent, TCP connections have established communication routes throughout the data exchange.

As a result of all of this, TCP is slower than some other protocols, but it does well in terms of reliability and security.

UDP

User datagram protocol (UDP) is another common choice for internet communication. It shines when used in applications that are highly time-sensitive, such as video playback.

The reason for this is that UDP connections don’t require a handshake before data can transfer. In fact, there is not a formal connection establishment process that precedes packet transfers.

As a result, UDP connections can send information right away, and this helps with raw speed and connection responsiveness. On the other hand, the lack of a handshake creates vulnerabilities and reliability issues that make UDP suboptimal for some types of transfers.

Major Differences Between the Two

The fundamental difference between TCP and UDP is the handshake. That one difference generates disparity between operations from one protocol to the other, and that’s why each is favored in a number of different applications.

Still, it’s important to understand the raw consequences of the handshake. UDP is considerably faster than TCP. At the same time, it loses many more packets, and it’s particularly vulnerable to DDoS attacks. These two issues are intolerable in some applications, which is why the slower option is still very popular.

Applications

In fact, it’s in a review of major applications that we can really understand the differing values from one protocol to the next.

Below, you’ll see six of the most common internet applications and which protocol they prefer. That will really lock in the advantages of each protocol and help you think about what you might want for any given application.

Streaming

Let’s talk about streaming first since it’s one of the most common communication types on the internet. Whether you’re streaming Netflix at home or an instructional video at work, streaming is better served by UDP.

That isn’t surprising since streaming relies on speed more than anything else. Especially because packet rates vary throughout the duration of a stream, the high responsiveness of UDP proves superior.

Browsing

What about browsing the internet? Even though you like it when web pages load very quickly, TCP is preferable for this one.

The big thing is that small delays are common when loading a page. TCP can exploit that small amount of downtime to ensure a stable and secure connection.

Even if it slows things down a little, web browsing is a situation where security is extra important.

Email

As for email, it’s obviously in the TCP camp. Email is an even more extreme example of having an opportunity to take more time to do things right. The time lost with TCP is rarely noticeable. Meanwhile, the stability of TCP improves email reliability. At the same time, TCP security benefits are certainly something you want for email exchanges.

Gaming

Gaming, however, is another story. This is yet another data situation where speed and flexibility are the most important. When playing online games, the lag introduced through handshakes can noticeably impact gameplay and general performance. For anyone optimizing their experience, UDP is just better.

File Transfers

Coming back to TCP, file transfers are a big one. In fact, this is a good chance to emphasize a point. The delays that exist in TCP happen when a connection is formed. In many cases, that connection doesn’t have to be reformed a bunch of times.

So, when you download a pack of files, you might get a short delay at the beginning (assuming you’re using TCP), but the handshake does not continuously slow things down for the duration of the download.

Now, you can see why TCP lag doesn’t matter too much for file transfers. They tend to take long enough that a little pause for a handshake isn’t really noticeable.

Meanwhile, reliability and security once again take precedence. If you lose too many packets in a file transfer, it can lower the integrity of the data in your download. Imagine if your device was installing automatic updates and the file was corrupted over your communication protocol. That’s a bad day, so the superior stability of TCP wins this category.

Live Communication

The last application category is live communication. This can include live video chat, VoIP, live chat messages, or any other real-time communication.

For everything in this classification, UDP once again shines. Speed and responsiveness are essential for live communications, clearly separating this category from something like email, where delays don’t matter.

With all of that covered, you should have a decent idea of what TCP and UDP are and where each works best.

Additional Learning Center Resources