WfW 3.11 was the first version to contain a TCP/IP stack, and the TCP/IP update disk for Windows 3.1 was released at the same time. It effectively upgraded 3.1 to 3.11.
I was there - the network stack (was designed to?) break WordPerfect 6, and I remember the grief it gave us, forcing us to choose between networking or word processing. That was a major factor in our office shifting from WordPerfect to Word.