If your PPP server uses PAP (Password Authentication Protocol)

Chapter 16. If your PPP server uses PAP (Password Authentication Protocol)

If the server to which you are connecting requires PAP or CHAP authentication, you have a little bit more work.

To the above options file, add the following lines

#
# force pppd to use your ISP user name as your 'host name' during the
# authentication process
name <your ISP user name>	# you need to edit this line
#
# If you are running a PPP *server* and need to force PAP or CHAP
# uncomment the appropriate one of the following lines. Do NOT use 
# these is you are a client connecting to a PPP server (even if it uses PAP
# or CHAP) as this tells the SERVER to authenticate itself to your
# machine (which almost certainly can't do - and the link will fail).
#+chap
#+pap
#
# If you are using ENCRYPTED secrets in the /etc/ppp/pap-secrets
# file, then uncomment the following line.
# Note: this is NOT the same as using MS encrypted passwords as can be
# set up in MS RAS on Windows NT.
#+papcrypt