TCP/IP stack fingerprinting is the passive collection of configuration attributes from a remote device during standard layer 4 network communications. The combination of parameters may then be used to

'nmap -sS' performs a TCP SYN (half-open) stealth scan to discover open ports, not to fingerprint the operating system.

'nmap -sT' performs a full TCP connect scan for port discovery and does not collect OS fingerprint data.

'nmap -sU' performs a UDP port scan; while '-p' specifies ports, this combination does not invoke OS detection or TCP/IP stack analysis.

The 'nmap -O' switch enables OS detection by sending a series of specially crafted probe packets and analyzing subtle differences in TCP/IP stack behavior such as TTL values, window sizes, and TCP options in the responses. Combining it with '-p' to specify ports ensures active ports are available for probing, improving fingerprint accuracy. This directly implements TCP/IP stack fingerprinting to infer the remote operating system.