3Com 10014299 manual PPP Overview, PPP Authentication Mode

12 CONFIGURING PPP AND MP

	This chapter contains information on the following topics:
	■	PPP Overview
	■	MP Overview
	■	Configure PPP
	■	Configure MP
	■ Display and Debug PPP
	■ Typical PPP Configuration Example
	■ Typical MP Configuration Example
	■ Fault Diagnosis and Troubleshooting of PPP
PPP Overview	The Point-to-Point Protocol (PPP) provides a standard method for transporting
	multi-protocol datagram over point-to-point links. It gains wide applications since
	it can provide user authentication, support synchronous/asynchronous lines and
	can be expanded easily.

PPP defines a whole set of protocols, including link control protocol (LCP), network control protocol (NCP) and authentication protocols (PAP and CHAP). Of them:

■ Link Control Protocol is used to negotiate some parameters of the link and is responsible for creating and maintaining the link.

■ Network Control Protocol is used to negotiate the parameters of network layer protocol.

PPP Authentication Mode

1PAP authentication

PAP (Password Authentication Protocol) is a 2-way handshake authentication protocol and it transmits username and password in plain text over the Internet. The process of PAP authentication is as follows:

The requester repeatedly sends its username/password combination across the link until the authenticator responds with an acknowledgment or until the link is broken. The authenticator may disconnect the link if it determines that the username/password combination is not valid.

2CHAP authentication

CHAP (Challenge-Handshake Authentication Protocol) is a 3-way handshake authentication protocol. It only sends the username but not the password across the link. The process of CHAP is as follows: