Cayman Systems 2E-H-W, User Manual

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How Your Cayman 2E-H-W Works Cayman 2E-H-W User’s Guide
C-6
November 2000
Each phase is described separately below.
Link Establishment
The manner in which a PPP link is opened depends on whether the
router's serial or Ethernet port is configured as a dial-in, dial-out, or
dedicated PPP interface:
Dial-in – If a port is configured as a dial-in interface, the router
sends an initialization string to the modem when it is turned on
to prepare it to accept calls. When the local modem receives an
incoming call and negotiates the serial connection settings, the
serial connection is established and the link peers begin
negotiating the link configuration.
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.
A port configured as both a dial-in and dial-out interface will
open a link if it receives a packet from either direction.
Dedicated – If a port is configured as a dedicated interface, the
router maintains a PPP link at all times. PPP over Ethernet links
are dedicated links.
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.