Dialing and Login
I use the excellent X-ISP utility to set up a PPP connection to my Internet Service Provider (ISP). X-ISP is available from, among other sources, The X-ISP Home Page, and is written and maintained by Dimitrios P. Bouras.
By my own experience, it is possible to start and stop PPP sessions from any user account (not only root) by setting the superuser bit for the programs xispdial, xispterm and pppd. The superuser bit can be set by the command chmod +s <filename> from the root account.
It takes some amount of effort to arrive at working TIMEOUT values for the Automatic Login - Expect/Send configuration in the Dialing and Login options window. This is the Dialing and Login configuration I use.