You could get all kinds of network stacks for msdos. Net ware, 3Com XNS, a weird proto Microsoft network I can’t recall the name of, banyan vines, decnet . Weird stuff for ibm token ring networks. And yep TCP as well. When lan manager was released you could run it over a choice of networks TCP included, because the original lan manager ran on Unix as well as OS/2 as the server.