I think TCP and IP were all one layer at one point. It's possible
the old IEN's, (which I'd heard would be on-line "soon" if
they're not already), would have
a spec for the combined TCP/IP, and it would probably use the terminology in
use at the time.
By the way, when I started at Digital to be the "Transport architect",
DECnet's layers were layer3=Transport, and layer4=Network Services.
Frankly I think Transport is a much better name for layer 3 than layer 4.
Layer 4 happens just at the endnode. It's layer 3 that actually
"transports" the data. Since I saw everyone getting confused when
they'd be talking about "Network layer" or "transport layer", which
was opposite in DECnet and OSI, I lobbied for changing the DECnet terms
(since we didn't have the clout to change the OSI terminology). Instead
of immediately swapping the names, we went through a few years of
neutral terms..."routing layer" for layer 3, and "end-to-end layer" for
One of the things I've been meaning to chase down is ... why did anyone
think "Transport" was a good name for layer 4? What does the word "transport"
mean that has anything to do with what layer 4 does?