"In part 1 we looked at a simple setup for creating and sharing a dial-up Internet connection. Today we'll learn how to build a dial-in server. A dial-in server is useful for remote system administration, remote user access, or building a low-cost WAN. A Linux dial-in server can serve as a gateway for both Linux and Windows boxes.
"There are three primary elements to a Linux dial-in server:
"A getty--'get tty'--is a daemon that monitors serial lines. Modems are represented by ttySN--/dev/ttyS0, /dev/ttyS1, dev/ttyS2, and /dev/ttyS3. There are all kinds of different Linux and Unix gettys. mgetty is especially good--it supports data, fax, and voice, and integrates nicely with pppd. If your system does not have mgetty, I recommend getting it..."