HOW QUAKE.EXE GOT ITS TCP/IP STACK

Summary from the TLDR Dev newsletter

In 1996, Quake faced challenges adapting to the shift from MS-DOS to Windows 95 while also supporting emerging technologies like 3D acceleration and the Internet. id Software created a single executable, quake.exe, compatible with both DOS and Windows by using djgpp's DPMI client and the Windows 95 DPMI server. For TCP/IP support in DOS, Quake relied on a costly third-party TSR, but in Windows 95, it utilized Mpath's "Chunnel" technology, a complex system involving virtual device drivers and DLLs to bridge the DOS executable with the Windows TCP/IP stack.