The default ppp timeout is 3 minutes. This can be adjusted with the line
set timeout NNN
where NNN is the number of seconds of inactivity before the
connection is closed. If NNN is zero, the connection is
never closed due to a timeout. It is possible to put this command in
the ppp.conf file, or to type it at the prompt in
interactive mode. It is also possible to adjust it on the fly while
the line is active by connecting to ppps server socket using
telnet
or pppctl. Refer to the
ppp man
page for further details.