A connection-oriented protocol that guarantees reliable, ordered, and error-checked delivery of data between applications.
TCP is the backbone of reliable internet communication. It powers the web, file transfers, and most client-server interactions where data integrity is critical.
Use TCP when you need accurate, complete data delivery - like for web pages, emails, or file downloads.
You need to know
Three-way handshake - Before data transfer, TCP establishes a connection with SYN, SYN-ACK, and ACK packets.
Reliable and ordered - It guarantees that data arrives without duplication and in the correct sequence.
Flow and congestion control - TCP adapts to network conditions to avoid overloading receivers or congesting the network.
Popular technologies
HTTP/1.1 and HTTP/2 - The protocols behind most websites, both use TCP.
FTP - File Transfer Protocol for uploading/downloading files reliably.
SMTP - Email protocol that relies on TCP for dependable message delivery.
Like posts like this?
Every week, you'll get a new system design concept, broken down like this one.
Free subscribers also get a little bonus:
🎁 The System Design Interview Preparation Cheat Sheet
If you're into visuals, paid subscribers unlock:
→ My Excalidraw system design template – so you have somewhere to start
→ My Excalidraw component library – used in the diagram of this issue
No pressure though. Your support helps me keep writing, and I appreciate it more than you know ❤️