Rapaire - and others interested

For a simple Windows network, it is pretty easy to hook several computers (PCs) through a single dialup line. The modem in ONE PC connects to the telephone line, and shares the connection with any and all other PCs that connect to it via an ethernet LAN. The telephone line sees all the using computers as one, and the "master" computer assigns and switches messages to the "user" PCs.

This is not a particularly elegant connection, but it's been built into Windows since at least Win98. (It was sort of there in Win95, but didn't seem to work even as well as in later versions.)

Theoretically, when any of the "user" PCs wants to connect, the "master" computor will dial the connection for them. I've found that this works pretty well. The real problem is that when a "user" PC is on a connection that gets "dropped," the modem PC may not recognize that the link is gone, and may also "misplace" the user. It is sometimes necessary to go to the master PC, kill the connection, and "refresh" from the user PC to get things back up.

In order for this to work, you need to have the whole bunch of PCs all on an ethernet LAN, as a WorkGroup. (Other kinds of LAN configurations might work, but I haven't tried any others.) Install Windows ICS (Internet Connection Sharing) on the ONE PC that has a modem connected to the phone line. Except for enabling ICS on the "host" computer, you set up all the internet stuff as if it were the only one using the connection.

Since the host PC does the DHCP assignments for traffic on the LAN, and the built-in facility for this is very primitive, you can run into some problems if you have (as I do) other "addressable" equipment on the LAN. I have two printers on ethernet print servers that do occasionally get into the act. The workaround is to be sure that the "extra" ethernet stuff is all assigned as high an address as feasible, to keep it away from the more or less random addresses that the host choses to assign to the users.

If you have multiple external devices (USB devices, perhaps) you can run into link-loops on your LAN. Win2K allows you to set protocols to handle this. WinXP does a very good job of setting things up for you automatically. Older, and lesser, OS versions can give you some real difficulties here, although such problems seem not to be too common.

I have had this setup using Win98 in the host, but it didn't really get usable for me until the host was replaced with the current Win2K machine. (I had not really "worked" the problem with the earlier setup.) I have had as many as 7 PCs connected to the LAN at the same time, with Win95, Win98, Win2K, and WinXP in the "user" machines all at the same time. Any connected machine could use the shared connection. I don't recall ever having more than 4 "on the net" at the same time, and I believe that the specs say there is a limit of 8 "shares" for ICS due to the limited host DHCP abilities.

Definitely not the "best" setup, but perfectly workable, especially if you're putting up with a POTS connection.

John