TCP vs UDP — What’s the Difference Between Them?


What Is the Internet Protocol?

The internet protocol (IP), which is a form of network protocol, is a collection of rules that govern how data is sent or transmitted to a specific recipient over a local network, subnets, or the Internet. When you send data from your web browser to a website, such as when ordering dog treats in bulk from your favourite pet supplies website, you are using the internet protocol.

Internet protocol data transmissions, in a roundabout way, allow you to do everything you do online, from tweeting and researching recipes to sending emails with photos or your favourite cat videos. It is, in essence, the internet’s base.

IP, TCP, and UDP Are All Protocols Within the Layers of the OSI Model

IP is a network protocol, as I previously said. The network is one of seven layers in the open systems interconnection (OSI) model established by the ISO. The model serves as a vertical structure and set of standards for how data is exchanged between computing systems. The OSI model is divided into seven layers:

  1. Physical layer
  2. Data link layer
  3. Network layer
  4. Transport layer
  5. Session layer
  6. Presentation layer
  7. Application layer

TCP and UDP, on the other hand, are two protocols that belong to the OSI model’s transport layer. There are now a number of protocols that fall within the seven layers and perform various purposes, many of which are based upon one another. We won’t go into all of them today because the aim of this article is to help you understand the differences between TCP and UDP.

You must first understand how the internet protocol functions before we can get into the nitty-gritty of addressing the differences between TCP and UDP. Since TCP and UDP both depend on IP, I claim this. This will act as a basis for the other two principles to be explained.

How the IP Works to Transfer Data

Routing is the mechanism by which data moves back and forth across the internet, regardless of what you’re sending. As you would expect, routers or gateways are used to control traffic in this phase. Routers are usually for related networks, while gateways help to connect dissimilar networks, according to a TechRepublic article by network engineer and tech writer Brien Posey.

To ensure that the data reaches the intended recipient, each computer is assigned its own IP address, similar to how your home or apartment has a unique address. If you’re using a regular IPv4 address, your IP address on the internet could look like instead of 123 Main Street. This 32-bit number is made up of a set of subnets (number segments separated by periods), each of which can hold up to three digits (for up to a total of 12 digits or 15 characters, including the periods).

Of course, this is not the case for IPv6 addresses, which are 128-bit numbers that look something like this: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 (this is an example IPv6 address from Wikipedia).

Before transmitting your data, the IP divides it into smaller PDUs, which are referred to as packets (for TCP) or datagrams (for datagrams) (for UDP). In networking, packets is the most widely used term for data units. This data breakdown occurs for all IP data transfers, including TCP and UDP. A label (header) is slapped on each of these individual little packets of data, telling the delivery person where it needs to go and where it came from.

The data is sent across the internet through routers or gateways that keep track of different IP addresses (and their corresponding domains). The data is passed from one portal to the next until one of them recognises the destination of the package or datagram.

Please remember that this is a (extremely) simplistic explanation of how IP functions. Only remember this example because I’ll come back to it later and use TCP and UDP as distribution methods.

If you’re wondering where the domain name system (DNS) falls into all of this (since it’s what binds domains to their IP addresses), know that it’s connected but different. The domain name system, for example, will make DNS requests using UDP. However, we won’t go into all of that here because it’s a completely different operation, and the purpose of this article is to concentrate on the differences between TCP and UDP. As a result, we’ll have to go over the DNS system in greater detail in a later post.

The Internet Protocol is the Delivery Service of the Internet

Now, let’s bring it into perspective. Consider the internet protocol to be the FedEx, DHS, or USPS of the internet, but with a twist (more on that later). You may opt to submit packages through standard delivery or have someone sign for them when they arrive to ensure they’ve reached the right person with these types of mail delivery services. The internet protocol, which is used for digital data transfers, operates in a similar way.

Continuing with the delivery service example, imagine that your mother wants to give you a BUNCH of home baked goodies, including cookies, breads, dehydrated fruits, and so on. (You’re such a lucky devil.) To do so, she’ll need your address to ensure that the oversized package arrives at your doorstep safely. Otherwise, those delectable treats could end up in the hands of Greg and Jill, your least favourite neighbours (and nobody wants that).

So, in this situation, your mother will box it up, mark it with your address (header), and call her preferred delivery service to come pick them up. (Again, I’m simplifying things a lot here, so bear with me.) However, since the package is too large to tackle, she is forced to break it down into a series of smaller labelled boxes (packets or datagrams).

As the packages exit her home, they arrive at the transfer station (gateway), where they will be routed to the next closest delivery point. The packages then travel from station to station (gateway to gateway) before they reach the one who knows your precise address.

Consider that the delectable kit is actually data being transmitted through the internet. Now, depending on whether the packages are delivered via TCP or UDP, what happens to them at this point can differ. I’ll clarify what I mean later, but first, let’s review what TCP and UDP are and what each data transmission protocol entails.

TCP vs UDP: Everything You Need to Know About These Protocols

What Is TCP?

Transmission control protocol (TCP) is a type of connection-oriented data communication protocol. It was created to assist in the establishment of secure connections on virtually every network, even unstable networks. TCP is part of the ISO’s open system interconnection (OSI) model’s transport layer, which is based on IP. It’s a transport layer communication protocol, so it’s called that.

However, how can you tell if you’re using TCP? You know how often when you try to load a high-quality video on your favourite video website, a buffering icon appears? That’s usually an indication that the data you’re getting is being sent over TCP.

TCP’s primary objective is to be an error-free data transmission protocol. The transmission control protocol aids in the following tasks:

Ensure that the receiver receives all of the data sent (via a delivery receipt) and keep data transmissions organised by ensuring that packets arrive in the order they were intended.

TCP accomplishes this by maintaining a secure link that allows it to check that packets are successfully received. Basically, if the data arrives as anticipated, in the correct order, the receiver confirms it. If this is not the case, the TCP will request that the sender submit the data again.

The Internet Engineering Task Force (IETF) first described the TCP protocol in RFC 761 in 1980. In 1981, it was superseded by RFC 793. It’s been a popular form of data transmission for a long time, and you probably use it on a regular basis as you go about your business on the internet.

However, it isn’t flawless, and it might not be the best protocol to use in all situations. UDP (or other communication protocols) are used in this case. (I’ll come back to UDP later.)

How TCP Works in Exchanging Data

Before transmitting data packets from the server to the device, the transmission control protocol needs a three-way handshake to create a link. The three-way handshake, which begins with the exchange of SYN, SYN-ACK, and ACK messages (also known as flags) between these individuals, aids in the establishment of a secure link.

The three messages are the following:

  • SYN — synchronize
  • SYN-ACK — synchronize-acknowledgement
  • ACK — acknowledge

There are a variety of other flags that can be traded after that, but we won’t go over them all right now. Let’s just get back to the point of the operation. Each segment of data sent from the client to the server is accompanied by an ACK flag to confirm receipt of the data packet once the link is created.

All of this sounds fantastic in principle. But where will you see a real-world example of TCP in action? Netflix, an internet video streaming service, was using TCP as of June 2016. (However, they never replied to my press request, so I’m not sure if they still do or if they use a different protocol now.)

What Is UDP?

UDP stands for user datagram protocol, as previously mentioned. It’s similar to TCP in that it’s a transport layer communication protocol, but it’s different in that it’s a connectionless communication protocol, which means it doesn’t need you to create a connection until sending your data packets (or, more specifically, datagrams).

Until transmitting data to the intended recipient, UDP does not require a three-way handshake. As a result, all or some of the data will arrive — and it may (or may not) arrive in the expected order. As a result, it’s often referred to as a “best effort.”

A user on the forum called Mike Robinson came up with a brilliant analogy to explain the user datagram protocol:

UDP puts a message into a bottle and tosses it into the sea. It might never arrive. It might arrive before or after some other bottle. You will never know if it arrived. You don’t even know if the intended recipient is alive at all, much less pulling bottles out of the water. The only way you’ll know if your message was heard is if another bottle washes up on your shoreline, and you manage to grab it before it sinks.”

UDP, like TCP, has been around for quite some time. In 1980, the IETF RFC 768 specified the user datagram protocol for the first time. Although TCP has long been the preferred protocol, UDP is gaining popularity as network efficiency and speed become more important.

How UDP Works in Exchanging Data

The advantage of UDP over TCP is that it has a lower latency, but it also means that some data and data confidentiality can be lost. And, unlike TCP, if any of the data is missing, the sender will not resend it because they have no way of checking to see if you got anything.

All of this is to conclude that UDP isn’t an error-free method of data transmission. Although it is a faster data transfer process than TCP, it comes with the caveat that you will not receive the data exactly as it was sent, and there may be data missing (which you will never notice).

UDP is suitable for “live” situations where data transfers must occur without delay in real time. Online video game play and audio or video calls are two examples of potential UDP use cases.

A Summary of the Differences Between TCP and UDP

TCP and UDP are essentially protocols that help decide how data is shared between two entities. The most important distinction between TCP and UDP delivery methods is:

  • Whether and how they are related. The relation is at the heart of TCP. It’s a protocol that establishes secure connections before sending data, even over insecure networks. UDP is a connectionless protocol, which means it can send data regardless of whether the recipient is available to receive it.
  • Completeness and dependability of data TCP prioritises data integrity and assured delivery over speed at the cost of data loss, while UDP prioritises speed over data integrity.
  • Speeds of data transfer TCP is a heavyweight challenger, while UDP is the champion of the light-weight category. The first follows a set of procedures to ensure that the job is done correctly, while the second is concerned only with getting the job done quickly.
  • Each protocol has its own applications. TCP is better for providing high-quality data streams that can buffer (such as video streaming services), while UDP is best for real-time data transfer applications such as audio and video chats, online gaming, DNS requests, and so on.

TCP vs UDP: Differences in Terms of Data Delivery (an Example)

Consider the distribution methods of TCP and UDP in the context of your mother’s home-baked goodies. When the distribution company transports the baked goods, the packages will be shipped to their destinations via various delivery routes. They may or may not arrive in the expected order or state, and they may simply be left without confirming that you are available to receive them.

The smaller data packets (baked items) arrive through TCP, and it’s as if you have a personal delivery assistant who reassembles them in the exact order they were sent to you by your mother. As a result, nothing from the original package has been altered or removed, and you must sign for the package when it arrives. Your mother will be able to ensure that you receive your gifts in this manner. She’ll know if one goes missing and will try to resend it.

The datagrams (baked items) in UDP, on the other hand, can be changed or rearranged in terms of order. When they arrive at their destination, they’re simply left on your doorstep with no one to sign for them and no service to reassemble anything for you. This means that if you only obtain any of the baked goods, it’s too bad because your mother isn’t aware of the situation and will not resend the missing ones. Furthermore, since you received a large number of parcels, you might not notice that one or two was missing.

TCP vs UDP Applications: When Is One Method Better Than the Other?

TCP is the protocol to use if you want a secure data transmission stream. TCP guarantees that you receive anything exactly as it was sent, and you don’t mind if there’s a pause or if you have to try again if there’s a connection rejection. However, if you’re more concerned with speed and want to retrieve data as soon as possible, regardless of whether it’s received exactly as it was sent — or whether data packets are missing — UDP will suffice.

Choosing between the two protocols is essentially a matter of what you want to achieve. Using real-time video and audio chats online or playing multi-player or battleground games in live online games are two examples of when UDP will be preferable to TCP.

TD;DR — The Key Differences Between TCP vs UDP

Look, I understand. You’re pressed for time, and there’s a lot to learn about TCP and UDP. Both of these protocols have their own set of benefits and applications in today’s digital world. So, for those of you in a rush, here’s a table that summarises the differences between TCP and UDP.

TCP (Transmission Control Protocol)UDP (User Datagram Protocol)
TCP is a connection-oriented communication protocol.UDP is a connectionless communication protocol.
TCP data units are known as packets.UDP data units are commonly referred to as datagrams (although they’re sometimes called packets as well).
TCP rearranges data packets to be received in their intended order.UDP sends datagrams independently, meaning that they may arrive in a different order.
Uses a three-way handshake to establish reliable connections.UDP doesn’t use a handshake process.
TCP confirms data delivery receipts.UDP doesn’t use delivery receipts.
TCP results in higher latency.UDP is designed for faster data transmission.
TCP guarantees data delivery by prioritizing data integrity, completeness, and reliability.UDP prioritizes speed and often results in data loss.
TCP is ideal for reliable data transmissions.UDP is ideal for real-time data transfers and streaming to avoid delay.
Mark Funk
Mark Funk is an experienced information security specialist who works with enterprises to mature and improve their enterprise security programs. Previously, he worked as a security news reporter.