Note that he links to http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable http://blog.netherlabs.nl/articles

Note that he links to http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-s... which more or less explains what's going on.