TCP vs UDP: When to Use What, and How TCP Relates to HTTP
TCP (Transmission Control Protocol)
The TCP is one of the basic standards which define the rules of the Internet. It is a protocol which priortizes reliable data delivery and recovery by sacrificing its speed. It uses a 3-way Handshake Technique for establishing a connection and a 4-way Handshake technique for terminating it. It ensures reliability by using sequence numbers and acknowledgements. It automatically retransmits the lost or corrupted data packets. It is used in FTP, SSH and Telnet.
UDP (User Datagram Protocol)
UDP is an alternative to TCP in networking. While TCP focuses on reliable data delivery, UDP makes fast communication its first priority. It establishes low-latency connections between applications and decreases transmission time. Unlike TCP, it does not provide data recovery or packet sequencing, but it is also much less expensive than TCP. It becomes a great option for time-sensitive situations such as Domain Name System (DNS) lookup, Voice over Internet Protocol (VoIP) and media streaming.
Differences between TCP and UDP
TCP ensures secure delivery of data packets. UDP focuses on fast delivery of data packets.
TCP offers mechanism for retransmission and error recovery while UDP has no such mechanism.
TCP delivers the data packets in the exact order in which they were sent. UDP sends packets in an unorderly manner.
TCP is slow because of the overhead of error-checking. UDP has minimal overhead which makes it faster and efficient.
There is no support for broadcasting or multicasting in TCP, but UDP supports it.
TCP provides flow and congestion control and UDP does not.
Usecase of TCP and UDP
TCP Uses (Reliable & Ordered)
Web Browsing (HTTP/HTTPS): Ensures web pages load correctly.
Email (SMTP, POP3, IMAP): Guarantees messages and attachments arrive intact.
File Transfers (FTP, SFTP): Essential for accurate file copies.
Secure Shell (SSH): For secure remote logins and commands.
Online Banking/E-commerce: Requires high data integrity.
UDP Uses (Fast & Real-Time)
Video Streaming (Live): For live broadcasts where minor glitches are okay.
Voice over IP (VoIP/Video Conferencing): Minimizes lag for smooth calls (Zoom, Skype).
Online Gaming: Reduces latency for responsive gameplay.
DNS (Domain Name System): For quick lookups, though TCP is used for large zone transfers.
Broadcasting/Multicasting: Efficient for sending data to many users at once.
HTTP (Hypertext Transfer Protocol)
Hypertext Transfer Protocol (HTTP) is the foundation of data communication for the World Wide Web, acting as an application-layer protocol for transmitting hypermedia documents like HTML. It enables communication between web browsers (clients) and servers via a stateless request-response model.
HTTP and TCP
HTTP (Hypertext Transfer Protocol) is an application-layer protocol that runs on top of the Transmission Control Protocol (TCP), which operates at the transport layer. HTTP uses TCP to establish a reliable, connection-oriented session between a client (browser) and server to transfer web data.
Key Aspects of the Relationship:
Layering: HTTP is the top-layer protocol (Layer 7) for transferring web content, while TCP is the underlying protocol (Layer 4) responsible for transmitting packets.
Dependency: HTTP relies on TCP to guarantee that data arrives accurately and in the correct order, handling retransmission of lost packets.
Connection Process: Before an HTTP request is sent, a TCP connection must first be established via a "handshake" process.
Functional Division: TCP provides the reliable delivery mechanism (the "pipe"), whereas HTTP acts as the language to define the request/response (the "content" inside the pipe).
Port Utilization: HTTP commonly uses TCP port 80 (or 443 for HTTPS) to manage communication between web browsers and servers.