Protman.dos is a real mode driver stored in the Windows directory and enabled using a device=protman.dos command line in the config.sys file. It is used in support of real mode protocols such as Banyan Vines and 16-bit Data Link Control (DLC) protocol.

If lost it can be found in the Win98\Net7.cab

I believe, but I have not yet confirmed that Protman stands for Protocol Manager.