You might want to read my comment in the other subthread over here:

https://news.ycombinator.com/item?id=19867467

Also, thanks a lot for the reference, strangely the first time I hear of this book! However, I have to most strongly disagree with the claim of "three layers is enough.", and you'll hopefully come to understand why, after checking the above comment. Which, by the way, DOESN'T speak in favor of OSI AT ALL - nor in favor of IP, for that matter. Two brief quotes from over there:

"[…]

This does not mean that we should be doing OSI. Good grief, no. …

[…]

————

[…]

[22] Someone will ask, What about IPv6? It does nothing for these problems but make them worse and the problem it does solve is not a problem.

[…]"