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I don't really object to the first 4 layers of the OSI model as applied to the current network stack - it's a pretty useful model of the separation-of-concerns between, say, Cat5, ethernet, IP, TCP.

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Those are indeed 4 layers, but, as the author points out, those don’t map onto the bottom 4 layers of OSI cleanly.

The biggest thing I would point out here, which I only mentioned briefly in the article, is the division of layer 2 into the MAC and the LLC "sublayers". This is received wisdom today that is frequently repeated in textbooks and courses, but this whole concept of "sublayers" was invented (and then formalized into standards!) to resolve the OSI model's poor correspondence to many non-OSI technologies like Ethernet II and 802.11*. Not only does the OSI model have "too many" layers, it also has "too few". So this is a major way in which the OSI model is not some "idealized" or "genericized" model like people often claim, but rather an alternative model that is sometimes similar, sometimes different from TCP/IP.

It reminds me of the taxonomy of living things. The 8 levels (Domain, Kingdom, Phylum, ...) are useful at the top, but break down fairly quickly as we've learned how complicated life really is.

The last plant I looked up (Wisteria) doesn't really have a useful phylum or class classification, and has 7 non-mappable "clade" groups of which it is a member. They still teach the 8 levels though.

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