Subject: PPP and L2TP

From: [email-masked]
Date: Fri, 12 May 2000 10:09:13 +0200

Hi all,
we are reading various RFCs regarding PPP and L2TP in order to try to understand
the relationships between PPP and L2TP in the LNS system.
It seems to me that this argument isn?t treat of in none documents.

In particular, I do not have clear the behaviour of the LNS system when an
incoming call is received from the LAC.

We have supposed that a PPP peer (a remote dial-up user) starts to send LCP and
authentication packets to a LAC.
After receiving an authentication request message, with the FQDN "user@domain"
in order to understand the destination LNS, the LAC sets up a new L2TP session
(we supposed the tunnel has already been set up).
After the tunnel/session set up, the PPP remote user and the LNS will exchange
PPP packets directly (the LAC forwards them transparently).
The PPP state machine of the LNS is not started yet (it?s still in its ?PPP dead
phase?), while the PPP user is waiting for authentication ack/nack message.

I supposed (and this is what don?t understand) that the LNS, after
tunnel/session establishment, "must" send an LCP configure request to its PPP
peer (the user) in order to set up a PPP connection (the PPP connection of the
user will be restarted).
Is this true?
Are there other methods?

We argue that if the LNS does not send any LCP messages immediately after the
new L2TP session set up, the PPP remote user will wait for authentication
ack/nack, until the PPP connection will be teared down.
I do not have found this assumption on RFCs, so my question is: ?Is this a
requirement for an LNS? Or is only an implementative issue??

Moreover, even if the remote user is going to retry to send an authentication
request message again, this message will arrive directly to the LNS (after the
tunnel/session establishment, the LAC is transparently) that will silent discard
it (the LNS is still in its ?PPP dead phase?).

Thanks to all in advance for possible answers.