1 introduction, 1 ppp, Ppp introduction – Nortel Networks 8000 User Manual
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Nortel Secure Router 8000 Series
Configuration -WAN Access
6 PPP and MP configuration
6.1 Introduction
The section covers the following topics that you need to know before you configure PPP and
MP:
•
•
•
6.1.1 PPP
PPP Introduction
The Point-to-Point Protocol (PPP) is one of the link layer protocols that supports transmission
of multiple network protocol packets over a point-to-point link. PPP provides user
authentication and supports synchronous and asynchronous communications.
PPP defines a set of protocols, including:
•
The Link Control Protocols (LCP) set ups, terminates and monitor data links.
•
The Network Control Protocol (NCP) negotiates the format and type of packets
transmitted over a data link.
•
The authentication protocols containing Password Authentication Protocol (PAP) and
Challenge-Handshake Authentication Protocol (CHAP) provides network protection.
PAP authentication
PAP is a two-way handshake authentication protocol. Passwords send over the link in plain
text. The process of PAP authentication is as follows:
•
The authenticated sends its username and password to the authenticator.
•
The authenticator verifies them according to the local user list and returns a response
(accept or reject).
PAP provides an unsafe authentication because the password is sent in plain text. In addition,
since the peer sends user name and password repeatedly on the established PPP link until the
identity authentication finishes, it cannot avoid being attacked.
CHAP authentication
CHAP is a three-way handshake authentication protocol. Passwords are sent over the link in
encrypted text.
There are two kinds of CHAP authentication, the unidirectional CHAP and the bidirectional
CHAP.
Unidirectional CHAP authentication indicates that one end works as the authenticator and its
peer is to be authenticated. In practice, it is commonly applied.
Unidirectional CHAP authentication has two cases: You configure Authenticator with a user
name or configure authenticator without a user name. Nortel recommends you to use the first
configuration. In application, you use only the unidirectional authentication.
Issue 5.3 (30 March 2009)
Nortel Networks Inc.
6-3