TCP/IP Deep Dive

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TCP/IP Model Overview

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TCP Header Structure

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TCP Connection States

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TCP Flow Control

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TCP Congestion Control

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TCP Congestion Control Algorithms

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IP Addressing

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NAT (Network Address Translation)

NAT Types

• SNAT: Source NAT (outbound, changes source IP)
• DNAT: Destination NAT (inbound, port forwarding)
• PAT: Port Address Translation (many-to-one)

NAT Traversal Techniques

• STUN: Session Traversal Utilities for NAT
• TURN: Traversal Using Relays around NAT
• ICE: Interactive Connectivity Establishment

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Socket Programming

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Socket Options

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Common TCP Issues

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TCP Tuning Parameters

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UDP Characteristics

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Interview Questions

1. Explain TCP three-way handshake
2. SYN → SYN-ACK → ACK
3. Establishes sequence numbers both directions

4. Takes 1.5 RTT

5. Why does TIME_WAIT exist?

6. Ensures delayed packets don't corrupt new connections
7. Allows final ACK to be retransmitted if lost

8. Duration: 2 × MSL (Maximum Segment Lifetime)

9. How does TCP handle packet loss?

10. Timeout-based retransmission
11. Fast retransmit (3 duplicate ACKs)

12. Selective acknowledgments (SACK)

13. What is TCP slow start?

14. Initial congestion window = 1 MSS
15. Doubles every RTT until ssthresh or loss

16. Avoids flooding network initially

17. TCP vs UDP: When to use each?

18. TCP: Reliability needed (HTTP, databases)
19. UDP: Low latency, loss tolerant (gaming, video)

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