It had a variant "Windows 3.11 for Workgroups" (1993-11), which was the second Microsoft OS with built-in networking, after "Windows 3.1 for Workgroups" (1992-10).
I have actually used "Windows 3.11 for Workgroups" with some coaxial-cable Ethernet NE2000 cards, but I do not remember what network protocols were used.
With all earlier MS-DOS or Windows versions third party networking solutions had to be used.
My first job was at a bank that used Windows 3.11 on all the corporate desktops (late 90s). We had 10mbit ethernet IIRC.
Periodically someone somewhere would plug both ends of an ethernet cable into the wall sockets, causing a broadcast storm and every PC in the building would freeze - Not even the mouse pointer would move.
Oddly enough my MS-DOS machine while in grad school was networked via a product made by Apple that allowed it to connect to a Mac network. My only use was accessing the department laser printer, but that was huge.
That rings true with my memory, I left the Windows world shortly after 3.11 for Workgroups came out, and there was a lot of Novell around. My job was writing a healthcare information system that used a ISAM database hosted on a Novell server, just starting to investigate SQL.
*Update:* Yes, looks like it uses the networking stuff provides by MS-DOS.
MS-DOS has NETSTART.BAT and PROTOCOL.INI that initializes TCP/IP with IP address and subnet mask.
When you look how a passenger information system in the trains boots up you can see how it shows BIOS information (floppy drive connected, serial and parallel port available, no harddisks) then it boots MS-DOS, initializes a XMS RAM disk, initializes parallel port, loads Crystal ENDS2ISA ethernet drivers, microsoft DOS TCP/IP protocol driver, and TCP/P MEMM driver, and calls NETBIND.COM.
