# TCP vs UDP

Quick Reference: HTTP | WebSockets

# Quick Reference

# Clear Definition

TCP (Transmission Control Protocol) is a reliable, connection-oriented protocol that guarantees data delivery and ordering. UDP (User Datagram Protocol) is a fast, connectionless protocol that provides best-effort delivery without guarantees.

💡 Key Insight: TCP prioritizes reliability, UDP prioritizes speed. Choose based on your requirements.

# Core Concepts

# TCP Characteristics

• Reliable: Guarantees delivery, retransmits lost packets
• Ordered: Delivers packets in order
• Connection-oriented: Establishes connection before data transfer
• Flow Control: Prevents overwhelming receiver
• Congestion Control: Adapts to network conditions

# UDP Characteristics

• Fast: Low overhead, no connection setup
• Unreliable: No delivery guarantee, no retransmission
• No Ordering: Packets may arrive out of order
• Connectionless: No connection establishment
• Lightweight: Minimal header overhead

# Use Cases

# TCP Use Cases

1. Web Browsing: HTTP/HTTPS
2. Email: SMTP
3. File Transfer: FTP
4. Database: MySQL, PostgreSQL connections

# UDP Use Cases

1. Video Streaming: Real-time video (can tolerate packet loss)
2. Gaming: Real-time game data (low latency critical)
3. DNS: Domain name resolution (fast lookups)
4. VoIP: Voice over IP (low latency)

# Best Practices

1. Choose TCP: When reliability critical
2. Choose UDP: When speed/low latency critical
3. Handle Loss: Implement application-level reliability for UDP if needed

# Interview Tips

🎯 Interview Focus: Understand trade-offs and when to use each.

# Quick Reference Summary

TCP: Reliable, ordered, connection-oriented. Use for web, email, file transfer.

UDP: Fast, unreliable, connectionless. Use for video, gaming, DNS.

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