No, it's not true. You can implement something that can load a webpage from 99.9% of the world's web servers from a couple of RFCs in a day. But this ease of im

No, it's not true. You can implement something that can load a webpage from 99.9% of the world's web servers from a couple of RFCs in a day. But this ease of implementation means that for basically any issue where the specs give any degree of freedom, somebody will have deviated from the norm. (I've implemented TCP from scratch three times, one of those implementations basically ran the traffic of entire countries.) The real problem is that every step toward 100% gets progressively harder to find and debug. See e.g. [0] for a middle box that would mangle connections if it received two identical SYN packets, or [1] for a way in which almost all servers anyone currently runs are accidentally resilient to a certain kind of connection-killing packet corruption, but S3 isn't. [0] https://www.snellman.net/blog/archive/2014-11-11-tcp-is-harder-than-it-looks.html https://www.snellman.net/blog/archive/2014-11-11-tcp-is-hard... [1] https://www.snellman.net/blog/archive/2017-07-20-s3-mystery/ https://www.snellman.net/blog/archive/2017-07-20-s3-mystery/