Published: 17 Dec 2025 | Reading Time: 5 min read
Every time data moves across a network, whether it's loading a website, streaming a video, or playing an online game, it relies on transport layer protocols to reach its destination. The two most important protocols at this layer are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
In many respects, TCP and UDP are very similar as they connect devices and send data between them, but internally they follow quite different paths. TCP is a very useful technique if you want to be assured of the accuracy of the data, whereas UDP is designed to provide the customers with speed and very low latency. Knowing the difference between TCP and UDP is fundamental to be able to make the right protocol choice for modern networking applications.
In this blog, we break down how TCP and UDP work, compare their strengths and limitations, and explore where each protocol fits best in real-world scenarios.
TCP and UDP are the two main sets of rules which perform different functions in the transmission of data over networks. A knowledge of the differences between them is instrumental in the selection of the most appropriate one for definite applications.
TCP is a protocol that needs a connection between two communicating devices and thereby can maintain the delivery of data to a recipient device reliably. It creates a link by the three-way handshake mechanism and guarantees that all the packets will reach the goal in the right sequence and error-free. Therefore, the use of TCP is justified in situations where the data concern is of primary importance, and the data have to be kept in their original order, for instance, in web browsing, email, and file transfers.
UDP is a connectionless protocol intended for situations where efficiency and speed are more important than dependability. In contrast to TCP, UDP does not guarantee packet delivery or order, nor does it create a connection prior to data transmission. This makes UDP ideal for applications like live video or audio streaming, online gaming, and Voice over IP (VoIP), where occasional data loss is acceptable, and low latency is crucial.
While both TCP and UDP are transport-layer protocols, they function in entirely different ways. Understanding how they operate helps you choose the right one for your needs.
Connection Establishment: TCP initiates communication using a three-way handshake:
Data Transmission: Once the connection is established, data is transmitted in segments. Each segment is numbered, allowing the receiver to reassemble them in the correct order.
Acknowledgement and Retransmission: Upon receiving every segment, the receiver informs the sender. If the acknowledgement is missing, TCP resends the segment to make sure the delivery is reliable.
Flow Control: Through flow control mechanisms, TCP tries to avoid a situation where the receiver will be too much 'stressed' by the data. It changes the pace of the data transmission according to the receiver's readiness.
Connection Termination: After data transmission is complete, the connection is terminated using a four-step process involving FIN (finish) and ACK packets from both the client and server.
No Connection Establishment: UDP is a connectionless protocol. It just fires datagrams to the receiving side without arranging anything in advance.
Data Transmission: Data is broken down into separate packets known as datagrams, each having the full information for delivery.
No Acknowledgement: UDP does not require acknowledgements from the receiver, allowing for continuous data flow without waiting for confirmation.
No Retransmission: If a datagram is lost during transmission, UDP does not retransmit it. Error checking is minimal, limited to checksums for data integrity.
Although TCP and UDP both handle data transmission, they differ greatly in how they manage reliability, speed, and connection setup. Let's explore the core difference between TCP and UDP:
| Aspect | TCP | UDP |
|---|---|---|
| Connection Type | Connection-oriented; requires a handshake to establish a connection | Connectionless; no handshake required |
| Reliability | Ensures reliable delivery with error checking and retransmission | Does not guarantee delivery; no retransmission |
| Ordering | Delivers packets in the order they were sent | No inherent ordering; packets may arrive out of sequence |
| Speed | Slower due to overhead from connection management and error handling | Faster due to minimal overhead and no connection setup |
| Overhead | Higher, with a larger header size (20 bytes) | Lower, with a smaller header size (8 bytes) |
| Error Checking | Comprehensive error checking and correction | Basic error checking without correction |
| Flow Control | Implements flow control to manage data transmission rate | No flow control mechanisms |
| Congestion Control | Uses congestion control mechanisms to prevent network overload | No congestion control; can cause network congestion |
| Retransmission | Retransmits lost or corrupted packets | No retransmission of lost packets |
| Header Size | Larger (20 bytes) | Smaller (8 bytes) |
| Bandwidth Usage | Higher due to retransmissions and acknowledgements | Lower due to minimal control overhead |
| Latency | Higher latency due to error checking and retransmission | Lower latency; suitable for real-time applications |
| Data Segmentation | Supports segmentation and reassembly | No built-in segmentation; relies on the application layer |
| Security | More secure due to built-in error handling and encryption options | Less secure, but can be combined with encryption protocols |
| Multicasting | Does not support multicasting | Supports multicasting, which is useful for broadcasting |
| Use Cases | Web browsing, email, file transfers, and remote access | Streaming, online gaming, VoIP, and real-time applications |
| Suitability | Best for applications requiring accuracy and reliability | Best for speed-sensitive applications with some data loss tolerance |
| Packet Loss Handling | Detects and recovers from lost packets | Does not recover lost packets |
| Application Examples | HTTP, FTP, SSH, SMTP | DNS, DHCP, VoIP, live video streaming |
TCP prioritizes reliability and correctness, while UDP prioritizes speed and timeliness. If your application cannot tolerate data loss or disorder, TCP is the right choice. If low latency and real-time responsiveness matter more than perfect delivery, UDP is the better fit.
While TCP and UDP have different functions and different characteristics of operations, they also have a number of significant similarities as the main transport layer protocols:
Transport Layer Protocols: Both TCP and UDP operate at the transport layer of the Internet Protocol Suite, facilitating communication between devices over networks.
Packet-Based Data Transmission: Each of the protocols divides data into packets for sending, and these packets are the ones that are joined again at the destination.
Use of Port Numbers: TCP and UDP both use port numbers to direct data to the correct application or service on a device, enabling multiplexing and allowing multiple applications to communicate simultaneously.
Header Structure: Both protocols add headers to their packets, which contain essential information such as source and destination port numbers, enabling proper delivery and handling of data.
Network Communication: TCP and UDP can both operate on the same physical network infrastructure and use IP for routing packets between devices.
Multiplexing: Both protocols promote multiplexing which means that they allow multiple communication streams over a single network connection.
Support for Data Distribution: While UDP natively supports broadcasting and multicasting, both protocols are fundamental for distributing data across networks and underpin many core internet services.
TCP and UDP are two related but different transport-layer protocols that are necessary for network communication to be possible over the same physical infrastructure. They are both packet-switched, use port numbers for delivery at the application level, and support multiplexing, which means that multiple services can be run simultaneously. Both protocols add headers to the data in order to be able to manage the transfer, and they are at the core of data distribution on networks, thus they are the foundation of modern internet communication.
To truly understand the UDP and TCP differences, it's important to weigh the strengths and limitations of each. Let's explore the particular benefits and drawbacks of TCP.
TCP is a communication protocol that is dependable. To put it simply, it guarantees that the data that is sent will be received by the intended recipient in full and without any errors. Part of the reason for this reliability is the use of acknowledgement packets, retransmission of data that is lost, and error-checking methods.
Example: When you download a file from the internet, TCP is the one who makes sure that every single piece of the file that is sent is also the one that is received. In case a packet is lost, TCP asks for it to be sent again to avoid giving you a file that is broken.
TCP provides error detection and correction methods to keep data accurate. It employs a checksum to identify errors in the data packets that have been sent. When an error occurs, the receiver eliminates the faulty packet, and the sender retransmits it by default.
Example: TCP guarantees that all financial data reaches the server error-free in safe transactions, such as online banking, avoiding possible inconsistencies.
TCP makes sure that every packet will be delivered in a proper order. Each packet is given a sequence number so the receiver can put them in the right order. When packets are out of order, TCP puts them back in order before handing them over to the application.
Example: Protocols such as TCP that are used in the case of email services like Gmail make sure that email data packets are received in the correct order so that emails appear properly formatted.
TCP has a higher overhead compared to UDP because it includes additional features like connection establishment, error correction, and packet sequencing. This leads to larger packet headers (20 bytes), increasing bandwidth consumption.
Example: In video streaming, employing TCP may result in a waste of resources as the protocol generates extra data for the purpose of reliability, which in turn causes it to be slower than it would be without these data.
As TCP is a connection-oriented protocol, it needs acknowledgements for each data packet and retransmissions of missing packets, thus it introduces latency. Therefore, it is not a good choice for applications in which data has to be transmitted in real-time, such as video calling and online gaming.
Example: In online multiplayer games, TCP would slow down performance due to constant packet verification, causing lag.
Moreover, the use of TCP demands the processor to work more and requires more RAM to be able to handle the connection management, acknowledgements and retransmissions. That is why it is not a very good performing solution for high-speed applications.
Example: For scalable IoT devices with minimal resources, the use of TCP may result in a high consumption of processing power; thus, the overall system performance may be degraded.
While comparing TCP and UDP, it can be inferred that UDP is faster but less reliable than TCP. The pros and cons of this protocol will help us clarify in which situations choosing it would be more appropriate.
UDP has a much smaller packet header (8 bytes) compared to TCP (20 bytes), reducing the amount of extra data sent with each packet. This low overhead makes UDP faster and more efficient for real-time applications.
Example: In live sports streaming, the use of UDP allows the video to be displayed continuously and smoothly without any kind of buffering.
UDP is designed for speed. Since it does not establish connections or require acknowledgements, it allows continuous data flow, making it ideal for time-sensitive applications.
Example: In VoIP (Voice over IP) calls, voice transmission is carried out in real-time with the help of UDP; thus there are no delays, and the user gets a more satisfactory experience.
Broadcasting and multicasting are possible with UDP, unlike TCP, which means that the data can be sent to several devices at the same time. Programs such as DNS (Domain Name System) and live video streaming can take advantage of this feature.
Example: By using UDP, a multiplayer online game can share the same game update with different players at the same time, thus making the gameplay smooth and uninterrupted.
UDP does not promise that packets will be delivered to the destination. In case a packet is missed, UDP does not send it again; thus, there could be data loss.
Example: During an online call, a lost UDP packet may result in a brief audio glitch.
UDP does not give sequence numbers; packets can be received in disorder. Programs that use UDP have to develop the ways of reordering on their own.
Example: If UDP is used for video streaming, some frames might arrive in the wrong order, causing visual glitches.
While TCP manages data flow, UDP is not such a regulated tool and thus is susceptible to network congestion. The situation may arise where numerous UDP packets are sent at a time so that the network becomes overloaded and loses some of its packets.
Example: In live gaming, if too much UDP traffic is sent at once, some packets might get dropped, causing delayed actions in the game.
Each protocol serves a unique purpose in networking. Let's explore where TCP and UDP are most commonly used and why one might be preferred over the other.
TCP is a perfect match for situations where the data needs to be correct and in the right sequence, due to its reliable, connection-oriented nature. Let's explore some common uses of TCP in everyday networking.
Web browsing is among the top most popular activities which rely on TCP. TCP is used by both HTTP and HTTPS to make sure that the web data is sent fully and properly. When a user enters a web URL in a browser, TCP is the one that initially makes a connection between the browser and the web server. This connection is what enables the data to be sent in an orderly and dependable way, thus the webpage loads correctly without any parts being left out or getting corrupted.
Email communication is very much reliant on TCP to be correct and complete. The three major email protocols that operate over TCP are:
Emails are made up of text, attachments, and metadata, thus TCP is the protocol that assures the whole message is kept intact when it is delivered. Email files that are lost or damaged on the way to the destination are eliminated by the error-checking and retransmission operations.
File transfer applications require high reliability, which TCP provides through protocols like:
TCP ensures that large files are divided into packets, transmitted sequentially, and reassembled at the destination without corruption. If a packet is lost, TCP retransmits it, guaranteeing data integrity.
Remote access protocols make use of TCP to set up a safe and dependable connection of a single user to a different computer or a server. These are:
TCP is the reason why the commands given by the user and the answers coming from the remote device are sent without errors, thus giving the user a smooth experience of controlling the remote device.
As UDP is portable and quick, it may be used in situations where speed is more important than correctness. Let's examine a few typical applications of this protocol in the real world.
Multiplayer online games require real-time data transmission, making UDP the preferred protocol. Since speed is more important than guaranteed delivery, UDP enables:
These are common FPS (First-Person Shooter) games, racing games, and battle royale games, where being able to react immediately is of utmost importance.
Streaming services and live broadcasts use UDP to deliver content quickly and efficiently. Examples include:
UDP allows minor packet loss without interrupting the stream, ensuring smooth playback.
Voice over IP (VoIP) applications such as Skype, Zoom, and Microsoft Teams utilize UDP in order to have communications with low latencies. In fact, if packets that have been lost are to be retransmitted in real-time conversations, delays as well as a voice with a robotic kind of distortion can occur. For this reason, UDP is in charge of speed, thus it is guaranteed that the talks keep on going as if there was no interruption.
DNS translates human-readable domain names (e.g., google.com) into IP addresses. Since DNS queries must be fast, UDP is used for quick request-response cycles. If a packet is lost, the client can simply resend the request without significant delays.
Selecting the right protocol—TCP or UDP—depends on your application's requirements, network conditions, and the performance characteristics you need. Here's a clear guide to help you make an informed decision:
| Requirement | Choose TCP | Choose UDP |
|---|---|---|
| Data integrity & order | Yes | Not required |
| Low latency | Not critical | Critical |
| Real-time responsiveness | Not required | Required |
| Occasional data loss | Not acceptable | Acceptable |
| Congestion control needed | Yes | No |
| Broadcasting / Multicasting | Not supported | Supported |
| Security (built-in) | Preferred | Add-on protocols needed |
Tip: There are some advanced applications on the border where they use TCP for sending accurate data and UDP for real-time media.
Knowing the performance difference between TCP and UDP is a must if you want to know which of these protocols is best for your app. The main factors to consider are power consumption, latency, scalability, and network resource consumption.
| Aspect | TCP | UDP |
|---|---|---|
| Bandwidth Utilization | Higher, due to protocol overhead | Lower, minimal overhead |
| Latency | Higher, not ideal for real-time applications | Lower, suitable for real-time communication |
| Scalability | Limited by connection state | Highly scalable, stateless |
| Congestion Control | Yes | No |
| Broadcast / Multicast | Not supported | Supported |
| Resource Usage | Higher (stateful protocol) | Lower (stateless protocol) |
Security is an important factor when choosing between TCP and UDP, as each protocol offers different features and faces unique vulnerabilities.
| Aspect | TCP | UDP |
|---|---|---|
| Connection Verification | Yes (three-way handshake) | No |
| Error Detection | Comprehensive (checksums, acknowledgements, retransmissions) | Basic (checksums only) |
| Encryption Support | SSL/TLS (widely used) | DTLS (must be added explicitly) |
| Vulnerabilities | SYN floods, TCP/IP stack exploits | DDoS amplification, spoofing, and reflection attacks |
| Authentication | Supported (via TLS/SSL) | Must be implemented at the application level |
In summary: TCP has more powerful security features and is more reliable, but it comes with higher overhead and latency, which makes it more appropriate for sensitive or mission-critical applications. In contrast, UDP is fast and resource-efficient, but it needs to be protected by additional security measures and used with caution so as not to cause security holes, especially in open or public networks.
The major difference between TCP and UDP lies in their balancing of speed and reliability. The accuracy of the data has to be the primary concern in the cases of just a few applications, such as web surfing, emailing, and file transfers, and hence TCP would be the best choice, i.e., a connection-oriented protocol that guarantees the emission of the data in a reliable, orderly, and error-free way. On the other hand, UDP is a connectionless protocol that mainly focuses on speed and resource-saving; thus, it is usually employed in real-time situations such as online gaming, VoIP, and live streaming. The decision to use either TCP or UDP is based on the needs of the application. When data integrity is an issue, TCP should be used, and when low latency and faster transmission that are required, then UDP is the right choice.
TCP is a connection-oriented protocol that guarantees reliable data delivery, whereas UDP is a connectionless protocol that focuses on speed rather than reliability. TCP ensures the order of packets and resends any that are lost, whereas UDP simply sends packets without checking for errors.
It takes a connection setup, acknowledgement, and retransmission to complete a process, so TCP methods are inherently a bit slow or add some latency. In comparison, UDP does not perform these reliability checks and thus sends the data at a much faster rate. Hence, UDP is a great choice for real-time applications.
You should use TCP when it is extremely necessary that the data be accurate, such as in internet browsing, sending e-mails, and conducting financial transactions. TCP alone will accomplish the delivery of all the data packets in the right order and without any loss, unlike UDP.
UDP is a low-latency protocol, which means that there is a very short lag time during data transfer, and also, the data transmission is done quickly. Thus, the protocol is very suitable for real-time applications such as gaming, video streaming, and VoIP, where small data loss is acceptable.
Yes, UDP is more susceptible to security breaches because it does not verify the connection or handle errors. But encrypting with DTLS can mitigate security quite a bit.
UDP does not keep track of lost packets, and therefore, it does not resend them. In the case of streaming, this can cause a small part of the video to freeze or lag, whereas in gaming, you might experience a slight lag, but the software continues running.
Yes. In most cases, a combination of both may be present i.e. UDP is exploited for rapid data streaming (gaming, video) while TCP is used for reliable transmissions (chat messages, authentication).
Both TCP and UDP are core transport layer protocols used for network communication. They operate on top of the Internet Protocol (IP), use port numbers to direct data to specific applications, and transmit information in the form of data packets. Additionally, both protocols support multiplexing, allowing multiple applications to communicate over a single physical network connection.
Both protocols can manage data distribution but broadcasting and multicasting are only supported natively by UDP. Yet, both TCP and UDP have the common features like sending data packets over networks, using headers for structuring packets, and operating in the same physical network environments. As a result, they become essential components for stable and effective communication in a network.
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