When PAP is used, the username and password are sent into a remote access server as a single LCP package, instead of the server sending a login request prompt and then waiting for a reply from the user.

There are certain instances where PAPs are considered useful:

1. When an installed software does not support CHAP or Challenge Handshake Authentication Protocol, a more secure authentication protocol

2. When there exists incompatibility issues between varied vendor implementations of CHAP

3. When there are certain events where a simple plaintext password should be available in order to simulate a login at a remote host