If a fetch request in browser runtime is aborted via the signal of an AbortController, what happens afterward?

More specifically:

How will the HTTP request be terminated? Will the sending/receiving of the HTTP request/response body proceed to finish if it is not fully sent out / received yet?

Will the underlying TCP connection be terminated? If so, is it terminated via a typical four-way handshake process or RESET directly? If so, is it still worth encouraging the use of AbortController against fetch considering it may take much time to establish a new TCP connection, especially when a bunch of requests is canceled consecutively such as auto-completing for search boxes?

If the underlying TCP connection will be re-used as usual, how could it be resumed from an incomplete HTTP request? (Is there some novel magic in HTTP/2 or QUIC?)

(I tried to search on the Internet, MDN, and the DOM standard which defines AbortController, to find nothing mention how aborting works under the hood at all. And the codebase of those browsers is too obscure for me to even locate where the implemtation is.)