That the data and transport layers are almost always intermingled, because the &quot;OSI network model&quot; you were taught about in school is basically a lie.<p>(At least inasmuch as it is claimed to describe anything in the real world. As a source of vocabulary, it&#x27;s at least OK, though it does suffer from people using numbers where I would rather they used the names of the layers. Much like RAID terminology is still impenetrable to me despite the several dozen times I&#x27;ve read the definitions.)