TCP vs UDP: Difference and Comparison

TCP (Transmission Control Protocol) ensures reliable, ordered, and error-checked delivery of packets, while UDP (User Datagram Protocol) is faster but unreliable and unordered.

Key Takeaways

1. TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures reliable and accurate data transmission by establishing a connection, verifying data delivery, and retransmitting lost packets.
2. UDP (User Datagram Protocol) is a connectionless protocol that offers faster data transmission without error-checking and connection-establishing processes, leading to possible inaccuracies in the delivered data.
3. The main difference between TCP and UDP is their approach to data transmission, with TCP prioritizing reliability and accuracy. At the same time, UDP emphasizes speed and efficiency at the expense of potential data inaccuracies.

TCP vs UDP

A connection-oriented protocol is TCP. TCP is slower than UDP in comparison. Data packet retransmission is only available with TCP and is more secure with 20 bytes header. While UDP is a connectionless protocol. UDP is a far faster, easier, and more effective protocol but is less secure than TCP.

However, the above is not the only difference. A comparison between both the terms on specific parameters can shed light on subtle aspects:

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Comparison Table

Feature	TCP (Transmission Control Protocol)	UDP (User Datagram Protocol)
Connection	Connection-oriented	Connectionless
Reliability	Highly reliable	Less reliable
Error checking	Yes, with retransmission and acknowledgments	No, only basic checksum
Ordering	Guaranteed order of data packets	No guaranteed order
Congestion control	Yes, uses flow control and windowing	No, sends data as fast as possible
Overhead	Larger header due to additional information	Smaller header, more efficient
Latency	Higher due to error checking and retransmission	Lower due to simpler protocol
Applications	File transfers, web browsing, email	Streaming media, online gaming, VoIP

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What is TCP?

TCP (Transmission Control Protocol) is a core communication protocol within the Internet Protocol Suite (commonly referred to as TCP/IP). It provides reliable, ordered, and error-checked delivery of packets over a network. TCP is connection-oriented, meaning it establishes a virtual connection between the sender and receiver before data transmission. Key features of TCP include:

1. Reliability: TCP ensures that data is reliably delivered to the intended destination by using mechanisms such as acknowledgment, retransmission of lost packets, and sequencing to ensure that packets are received in the correct order.
2. Flow Control: TCP employs flow control mechanisms to manage the rate of data transmission between the sender and receiver, preventing the sender from overwhelming the receiver with data.
3. Congestion Control: TCP includes congestion control algorithms to manage network congestion and prevent network collapse by adjusting the transmission rate based on network conditions.
4. Connection-oriented: TCP establishes a connection between the sender and receiver before data transmission. This connection includes a handshake process to negotiate parameters and establish communication.
5. Full-Duplex Communication: TCP allows for simultaneous two-way communication between the sender and receiver, enabling both parties to send and receive data concurrently.
6. Byte Orientation: TCP treats data as a stream of bytes rather than individual packets, allowing for efficient data transfer and reassembly at the receiving end.
7. Error Detection and Correction: TCP includes mechanisms for error detection and correction, such as checksums, to ensure the integrity of data during transmission.

 

What is UDP?

UDP (User Datagram Protocol) is one of the core protocols in the Internet protocol suite, operating at the transport layer. It is a connectionless protocol, meaning it does not establish a direct connection between the sender and receiver before transmitting data. Instead, UDP sends data packets, called datagrams, without guaranteeing their delivery or ensuring their order.

Key characteristics of UDP include:

1. Connectionless Communication: UDP does not establish or maintain a connection before sending data. Each datagram is independent of others, allowing for faster transmission since there is no need for handshaking or connection setup.
2. Unreliable Delivery: UDP does not provide reliability mechanisms such as acknowledgment of received packets, retransmission of lost packets, or error correction. Consequently, there is no assurance that all datagrams will reach their destination, and there may be packet loss or duplication.
3. Minimal Header Overhead: UDP’s header is lightweight compared to TCP, containing only essential information such as source and destination port numbers and the length of the datagram. This minimal overhead makes UDP efficient for applications that prioritize speed and low latency.
4. Broadcast and Multicast Support: UDP supports broadcast and multicast communication, allowing a single datagram to be sent to multiple recipients simultaneously, which is useful for applications like multimedia streaming or online gaming.

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Main Differences Between TCP and UDP

1. Connection-Oriented vs. Connectionless:
   • TCP is connection-oriented, meaning it establishes a reliable and ordered connection between the sender and receiver before transferring data. This connection involves a handshake process to set up parameters such as sequence numbers and window sizes.
   • UDP, on the other hand, is connectionless. It does not establish a connection before sending data. Each UDP datagram is independent of others, allowing for faster transmission without the overhead of connection setup and maintenance.
2. Reliability and Ordering:
   • TCP ensures reliable delivery of data by providing mechanisms such as acknowledgments, retransmissions, and sequence numbers. It guarantees that data will be delivered accurately and in the correct order.
   • UDP does not guarantee reliability or ordering of data delivery. It simply sends datagrams without ensuring that they reach their destination or arrive in the same order they were sent. This lack of reliability makes UDP faster but less suitable for applications that require guaranteed delivery, such as file transfer or web browsing.
3. Error Checking and Correction:
   • TCP includes error-checking and correction mechanisms to detect and recover from data transmission errors. It uses checksums to verify the integrity of data and retransmits lost or corrupted packets.
   • UDP does not perform error checking or correction. It relies on higher-layer protocols or applications to handle any errors that may occur during transmission.
4. Flow Control and Congestion Avoidance:
   • TCP implements flow control and congestion avoidance mechanisms to regulate the rate of data transmission and prevent network congestion. It adjusts the transmission rate based on network conditions and receiver capabilities.
   • UDP does not incorporate flow control or congestion avoidance. It sends data at the maximum possible rate, which can lead to network congestion if not managed by the application.
5. Header Overhead:
   • TCP headers are larger compared to UDP headers due to the additional control information required for reliable communication. TCP headers include fields such as sequence numbers, acknowledgment numbers, window sizes, and checksums.
   • UDP headers are minimal, containing only essential information such as source and destination port numbers and the length of the datagram. This minimal overhead makes UDP more efficient for applications that prioritize speed and low latency.
6. Applications:
   • TCP is commonly used for applications that require reliable, ordered, and error-checked delivery of data, such as web browsing, email, file transfer (e.g., FTP), and remote administration (e.g., SSH).
   • UDP is preferred for applications that prioritize speed and efficiency over reliability, such as real-time communication (e.g., VoIP, video conferencing), online gaming, DNS (Domain Name System) resolution, and multimedia streaming.

References

1. https://ieeexplore.ieee.org/abstract/document/751376/
2. https://smartech.gatech.edu/bitstream/handle/1853/12301/MANIACS_40.pdf?sequence=1&isAllowed=y

Last Updated : 10 February, 2024