Which protocol allows for the functionality of Wi-Fi connectivity?

The protocol that enables the functionality of Wi-Fi connectivity is 802.11. This is a family of standards established by the Institute of Electrical and Electronics Engineers (IEEE) for wireless local area networks (WLAN). The 802.11 standards define the methods for devices to communicate over the airwaves, thereby enabling wireless connectivity that we commonly refer to as Wi-Fi.

The various amendments under the 802.11 standard, such as 802.11n, 802.11ac, and 802.11ax, detail different enhancements and capabilities for wireless communication, including data rates, range, and security features. This makes 802.11 integral to how devices connect to networks wirelessly, facilitating everything from internet access to file sharing and online gaming across compatible devices. Other protocols mentioned serve different purposes; for instance, TCP is a protocol for reliable data transmission over the internet, while FTP and HTTP are protocols used for file transfer and web communications, respectively. These do not inherently provide the connectivity that 802.11 specifically does for Wi-Fi networks.