Subject: L2TP question

From: "Fabio Poggi" <[email-masked]>
Date: Thu, 21 Sep 2000 16:48:13 +0200

Hi all

I have a question about the relationships between PPP and L2TP in the LNS
system.
It seems to me that this argument isn't treat of in none documents (is it true,
first of all ?).

In particular, what is the behaviour of the LNS system when an incoming call is
received from the LAC.

   A PPP peer (a remote dial-up user) starts to send LCP and authentication
   packets to a LAC.
   After receiving an authentication request message, the LAC sets up a new L2TP
    tunnel/session by the FQDN "user@domain" (in order to understand the
   destination LNS).
   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 in its authentication phase.

What happens at this time ?
(I've not found the answer in any documents !)

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

If the LNS does't make any actions, the remote user will 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) and, here, it will silent discard
(the LNS is still in its "PPP dead phase").

Could anyone help me?

Thanks a lot in advance.

Fabio Poggi

---

From: [email-masked]
Date: Fri, 22 Sep 2000 08:57:39 +0200

You have several options:
- initialize ppp stack in the lns with proxy infos from iccn 
- restart lcp 
- restart authentication (if requested)
If possible make different options configurable
		Paolo
-----Original Message-----
From: Fabio Poggi [mailto:[email-masked]]
Sent: Thursday 21 September 2000 16:48
To: [email-masked]
Subject: L2TP question

Hi all

I have a question about the relationships between PPP and L2TP in the LNS
system.
It seems to me that this argument isn't treat of in none documents (is it
true,
first of all ?).

In particular, what is the behaviour of the LNS system when an incoming call
is
received from the LAC.

   A PPP peer (a remote dial-up user) starts to send LCP and authentication
   packets to a LAC.
   After receiving an authentication request message, the LAC sets up a new
L2TP
    tunnel/session by the FQDN "user@domain" (in order to understand the
   destination LNS).
   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 in its authentication phase.

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

Could anyone help me?

Thanks a lot in advance.

Fabio Poggi

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---

From: "Fabio Poggi" <[email-masked]>
Date: Fri, 22 Sep 2000 13:49:34 +0200

Hi Paolo,
the first option you suggest involves some optional L2TP AVPs (Proxy LCP AVPs
are not defined as mandatory either in RFC or in
draft-ietf-l2tpext-l2tpbis-00.txt), so could be reasonable that some LAC or LNS
doesn't implement these AVPs (and anyway LAC and/or LNS are not forced to do so
by none RFC).

The second and third options are not addressed in neither in RFC nor in
draft-ietf-l2tpext-l2tpbis-00.txt; these could be implementations caracterizing
some LAC, but not all LAC !!
It is reasonable to think that a LAC doesn't implement any of these mechanism
(since are not forced to do so by the L2TP RFC), wiht the conseguence of not set
up any kind of effective communication.

In the scenario I've explained in my previous mail, there is none indication
from L2TP RFC standard in order to resolve that problem.

The L2TP RFC seems to lack of a good explanation about the problem of L2TP-PPP
interaction and this could generate some interoperability problem.
It seems to me that a standardization, in an L2TP RFC document (for exemple in
draft-ietf-l2tpext-l2tpbis-00.txt ??), of the interaction between L2TP state
machine and the PPP automaton, either in the LNS or in the LAC or in both, is
necessary.

What do you think about ?

Thanks a lot.
Fabio Poggi

[email-masked] on 22/09/2000 08.57.39

                                                              

 To:      Fabio Poggi/MAIN/MC1@MCMAIN, [email-masked]         
                                                              
 cc:                                                          

 Subject: RE: L2TP question                                   

-----Original Message-----
From: Fabio Poggi [mailto:[email-masked]]
Sent: Thursday 21 September 2000 16:48
To: [email-masked]
Subject: L2TP question

Hi all

Could anyone help me?

Thanks a lot in advance.

Fabio Poggi

**** DISCLAIMER ****

---

From: [email-masked]
Date: Fri, 22 Sep 2000 14:22:06 +0200

Find my answers below

-----Original Message-----
From: Fabio Poggi [mailto:[email-masked]]
Sent: Friday 22 September 2000 13:50
To: [email-masked]
Cc: [email-masked]
Subject: RE: L2TP question

Hi Paolo,
the first option you suggest involves some optional L2TP AVPs (Proxy LCP
AVPs
are not defined as mandatory either in RFC or in
draft-ietf-l2tpext-l2tpbis-00.txt), so could be reasonable that some LAC or
LNS
doesn't implement these AVPs (and anyway LAC and/or LNS are not forced to do
so
by none RFC).

The second and third options are not addressed in neither in RFC nor in
draft-ietf-l2tpext-l2tpbis-00.txt; these could be implementations
caracterizing
some LAC, but not all LAC !!

I suppose here you mean LNS

It is reasonable to think that a LAC doesn't implement any of these
mechanism

Again LNS

(since are not forced to do so by the L2TP RFC), wiht the conseguence of not
set
up any kind of effective communication.

Read section 9.5 of rfc2661, it looks pretty clear to me

The L2TP RFC seems to lack of a good explanation about the problem of
L2TP-PPP
interaction and this could generate some interoperability problem.
It seems to me that a standardization, in an L2TP RFC document (for exemple
in
draft-ietf-l2tpext-l2tpbis-00.txt ??), of the interaction between L2TP state
machine and the PPP automaton, either in the LNS or in the LAC or in both,
is
necessary.

Thanks a lot.
Fabio Poggi

 

                                                              
 cc:                                                          

-----Original Message-----
From: Fabio Poggi [mailto:[email-masked]]
Sent: Thursday 21 September 2000 16:48
To: [email-masked]
Subject: L2TP question

Hi all

Could anyone help me?

Thanks a lot in advance.

Fabio Poggi

**** DISCLAIMER ****

**** DISCLAIMER ****