[hannesm]

The specification, as written in the RFC, is pretty useless... But luckily people sat down and formalised TCP/IP as spoken on the Internet (10 years ago, Linux-2.4.20/FreeBSD-4.6/Windows XP): https://www.cl.cam.ac.uk/~pes20/Netsem/index.html

All the code is now BSD licensed https://github.com/PeterSewell/netsem

What is missing in 10 years of TCP? Apart from SACK and delayed ACK not much it seems (in FreeBSD congestion control algorithms are pluggable nowadays).

And I currently revive it (working hard on test suite using DTrace probes) https://www.cl.cam.ac.uk/~pes20/HuginnTCP/

Please ping me if you're interested (hannes at mehnert dot org) and eager to help.