Cayman Systems 3220-H User Manual page 177

Cayman 3220-H User's Guide
December 2000
Dial-out -- If a port is configured as a dial-out interface, the router
opens a PPP link when an internal Network Protocol routes a
packet out the PPP interface. If PPP determines that the serial
connection is not open, the router passes a telephone number
and modem configuration information to the modem, which
calls the modem connected to the remote peer. When the two
modems establish a connection, the two peers begin negotiating
the link configuration.
Dedicated -- If a port is configured as a dedicated interface, the
router maintains a PPP link, typically over a leased telephone
line, at all times.
Link Configuration
Link Control Protocol (LCP) configuration options allow
modification to the standard characteristics of a PPP link to be
negotiated. Negotiable options include settings for the maximum
receive unit (MRU), asynchronous control character mapping, and
link authentication. If a configuration option is not negotiated (that
is, if a Configure-Request packet does not include a value for a
particular option), the default value for that option is assumed.
Once a serial connection is made, each peer negotiates its side of the
link's configuration by sending a Configure-Request message that
lists its complete set of proposed configuration settings. When one
peer sends a Configure-Request, the other peer responds in one of
three ways:
Configure-Ack -- If every configuration option in the
Configure-Request packet is both recognizable and acceptable,
the second peer returns a Configure-Ack message that lists the
complete set of proposed settings and indicates that the peer
accepts the settings. All configuration options are acknowledged
simultaneously.
Configure-Nak -- If every configuration option in the
Configure-Request is recognizable but some values are not
acceptable, then the second peer returns a Configure-Nak
message that identifies the unacceptable option settings and
How Your Cayman 3220-H Works
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