What is ISN? (TCP Initial Sequence Number Guide)
The Initial Sequence Number (ISN) is a 32-bit random value that marks the starting point for sequence numbers in a TCP connection. Exchanged during the “SYN” phase of the three-way handshake, the ISN ensures reliable data reassembly, prevents interference from delayed “ghost” packets, and protects against TCP sequence prediction attacks. How the TCP Handshake Uses…