Nortel Networks 8000 - Manual (Page 130)

6 PPP and MP configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
Configuring Authenticator with a user name.
The authentication procures are as follows:
- Authenticator sends a random generated "challenge" message together with the local
host name to the peer.
- The peer looks for its local password in the local users list based on the user name of
authenticator. Then it performs the MD5 calculation according to the password and
challenge message and responds authenticator with the calculated value and its own
user name.
- Authenticator checks the password of the peer based on peer user name and finds the
matching value. Then it also performs MD5 calculation and compares the calculated
value with that contained in the Response message. If the values match, the
authentication succeeds. Or the authentication fails.
Configuring Authenticator without a user name.
The authentication procures are as follows:
- With no user name, authenticator sends only challenge messages to the peer.
- The peer performs MD5 calculation based on the password configured on the local
interface and the challenge messages.
- Then the peer responds the authenticator with the calculated value and its own host
name. The other procedures are the same as the above case.
PPP link operation
Figure 6-1 illustrates the PPP link operation process.
Figure 6-1 PPP link operation process
To set up a PPP link, first enter PPP in the Establish.
In the Establish phase, LCP negotiation carries out on the PPP link. It includes the negotiation
of operating mode (SP or MP), authentication mode and maximum transmission unit (MTU).
After the successful LCP negotiation, the status of LCP is "OPENED", which indicates that
the bottom layer link has been set up.
If you configure the authentication, PPP enters the Authenticate phase and begins with the
CHAP or PAP authentication.
If the authentication fails, PPP enters the Terminate phase, and then the link is terminated and
LCP turns to "DOWN". If the authentication succeeds, it enters the Network Control Protocol
(NCP) negotiation phase. The status of LCP is still "OPENED" while the status of NCP
changes from "Initial" to "Request".
6-4 Nortel Networks Inc. Issue 5.3 (30 March 2009)