Sequence Of Events On The Lns - Juniper JUNOSE 11.1.X - BROADBAND ACCESS CONFIGURATION GUIDE 6-4-2010 Configuration Manual

JUNOSe 11.1.x Broadband Access Configuration Guide
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A PPP connection now exists between the client and the LNS.
NOTE: The router discards received packets if the size of the variable-length, optional
offset pad field in the L2TP header is too large. The router always supports packets
that have an offset pad field of up to 16 bytes, and may support larger offset pad
fields, depending on other information in the header. This restriction is a possible,
although unlikely, cause of excessive discarding of L2TP packets.

Sequence of Events on the LNS

The E Series router sets up an LNS as follows:
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NOTE: If proxy LCP is not present or not acceptable, the router negotiates LCP with
the remote system.
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Implementing L2TP
The client initiates a PPP connection with the router.
The router and the client exchange Link Control Protocol (LCP) packets. For
details about negotiating PPP connections, see the Configuring Point-to-Point
Protocol chapter in JUNOSe Link Layer Configuration Guide.
By using either a local database related to the domain name or RADIUS
authentication, the router determines either to terminate or to tunnel the PPP
connection.
If the router discovers that it should tunnel the session, it does the following:
a. Sets up a new destination or selects an existing destination.
b. Sets up a new tunnel or selects an existing tunnel.
c. Opens a new session.
The router forwards the results of the LCP negotiations and authentication to the
LNS.
An LAC initiates a tunnel with the router.
The router verifies that a tunnel with this LAC is valid destination configured,
hostname and tunnel password correct.
The router completes the tunnel setup with the LAC.
The LAC sets up a session with the router.
The router creates a dynamic PPP interface on top of the session.
If they are enabled and present, the router takes the proxy LCP and the proxy
authentication data and passes them to PPP.
The E Series PPP processes the proxy LCP, if it is present, and, if acceptable,
places LCP on the router in opened state without renegotiation of LCP.