DescentBB

Check this out. I haven't used it personally but I've heard rave reports of it working for many other people for games other than Descent. Basically it is a program that simulates LAN play over the internet.

http://www.hamachi.cc/

I don't really play Descent all that much but I felt compelled to register to tell you guys about it. It'd be cool if you guys could try it out and report back. No idea if it'd work with D1X or D2XW32.

That's what Kali does. It simulates a LAN (at least in the case of Descent)

Neat looking utility.

http://en.wikipedia.org/wiki/Hamachi

The Windows version handles IPX traffic. Thus, it would very likely work with Descent (and a great many other classic DOS games).