Cayman Systems 3220-H User Manual page 178

How Your Cayman 3220-H Works
C-8
proposes new settings acceptable to the second peer. A
Configure-Nak message may also include proposed
configuration settings for options that the second peer requires
but that the first peer did not include in its Configure-Request.
Configure-Reject -- If one or more of the configuration options in
a Configure-Request are not recognizable or are not acceptable
for negotiation, the second peer returns a Configure-Reject
message that identifies the rejected options. The first peer can
then send another Configure-Request that does not include any
of the options listed in the Configure-Reject.
The negotiation mechanism is conducted independently in each
direction: a setting negotiated for one peer does not apply to the
other peer until it negotiates that option for itself. For example, if
Peer A negotiates that it has a maximum receive unit of 1600 bytes
with Peer B but Peer B does not negotiate its own MRU (implying
that it uses the default value of 1500), then Peer A can send frames
up to 1500 bytes long to Peer B but Peer B can send frames up to
1600 bytes long to Peer A.
Authentication
The PPP protocol suite includes two optional methods (Password
Authentication Protocol (PAP) and Challenge Handshake
Authentication Protocol (CHAP)) to ensure that unauthorized users
do not access network services. By default, authentication is not
required as part of the PPP link process. However if a peer requires
authentication, it must negotiate the use of an authentication
protocol during the link establishment phase.
The manner in which each peer will authenticate the other is
negotiated during the link configuration phase, when each peer
specifies whether it requires authentication and, if it does, the
authentication method it uses. If a link peer requires authentication
(if it is an authenticator, in the terminology of RFC 1334), the other
peer must submit its name and authentication information before
the link can proceed. If the peer fails to send valid authentication
information, the authenticator terminates (closes) the PPP link.
Cayman 3220-H User's Guide
December 2000