Cayman Systems 2E-H User Manual page 131

Cayman 2E-H User's Guide
November 2000
Challenge Handshake Authentication Protocol (CHAP)– The
Challenge Handshake Authentication Protocol (CHAP) is a more
secure authentication method than PAP. CHAP authentication
involves three entities: a "secret" known to both link peers, a
random challenge value, and a sequential challenge identifier.
The authenticator sends a numbered message that includes a
challenge value to the remote peer. The remote peer uses the
secret to encrypt the challenge value and challenge identifier
using a one-way hash function, ensuring that the response
cannot be intercepted and used by an unauthorized user to
obtain a legal password. The challenge identifier ensures that the
encrypted authentication information cannot be recorded and
played back later to gain access by an unauthorized user.
Network Configuration
After a PPP link has been established and authentication has been
satisfied, PPP sends Network Control Protocol (NCP) packets to
configure one or more network layer protocols, such as TCP/IP.
Link Up
Once a network-layer protocol is configured, the PPP link is
considered up (open), and datagrams for that protocol are
exchanged over the link. Either peer can close a network-layer
connection without interfering with other network-layer
connections or the LCP connection. A PPP peer discards any packets
received when the corresponding NCP is not open.
Link Termination
A link can be terminated during initialization because a configuration
or authentication failure occurs. Once a PPP link is established, it
remains configured for communication unless explicit LCP or NCP
packets close the link or until some external event, such as the
expiration of an activity time or intervention by a network
administrator, occurs.
When a peer no longer needs a link, it sends a Terminate-Request
packet to the remote peer and closes any open NCP sessions. When
How Your Cayman 2E-H Works
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