Liangxu Linux

Feb 22, 2023 · Fundamentals

Why Does a TCP Client Send RST When SYN‑ACK Ack Number Mismatches?

The article explains that during TCP's three‑way handshake, if a client receives a SYN‑ACK with an unexpected acknowledgment number, it must send an RST to abort the stale connection, because silently discarding the packet would cause long retransmission delays and prevent the new connection from being established.