ppp passes the name of its controlling tty and the login name used by the remote host to pppd(ADMN) through a UNIX domain socket. pppd looks up the login name in /etc/ppphosts and configures a STREAMS stack over the controlling tty based on the /etc/ppphosts entry. ppp has no further requirements but does not exit so as to keep the tty line open for the PPP connection.
When the connection is no longer needed, pppd sends a SIGUSR1 to ppp. Upon receipt of this signal, ppp exits and the tty is closed. Additionally, ppp responds to the signals SIGHUP and SIGTERM by passing a close message to the PPP daemon and then exiting.
ppp normally sends the banner
SCO OpenServer PPP
to tell the client that it is running.
The -q option prevents
the banner being sent.
If the -u option is used to specify a login name, ppp will start without trying to obtain a login name and password from a remote login script. The name, which need not exist in /etc/passwd, is used to obtain details about a link's endpoint from /etc/ppphosts.