eap Mailing List: RE: Question on EAP statemachine

[Pasi.Eronen (Pasi.Eronen]

Mahesh,

I'm not very familiar with L2TP, but I thought the LAC 
is "below the PPP layer" (simply forwards PPP frames 
to the LNS), and thus it does not know anything about EAP?

But anyway, determining when a new EAP conversation starts
is done outside the peer state machine. If the lower layer
can do it, then the state machine supports it (but the
lower layer is then responsible for describing how the
results of the two EAP conversations should be combined).

Best regards,
Pasi

> -----Original Message-----
> From: ext Mahesh Kelkar [mailto:mkelkar [at] rocketmail.com]
> Sent: Wednesday, June 29, 2005 5:27 PM
> To: Eronen Pasi (Nokia-NRC/Helsinki); eap [at] frascone.com
> Subject: RE: Question on EAP statemachine
> 
> 
> Pasi,
> 
> This particular example refers to the L2tp setup as
> described below
> 
>  Peer         LAC               LNS
>   |---- PPP----|                  |             
>   |            |                  |
>   |            |---- PPP/L2TP ----|
>   |            |                  |
>   |            |<--L2TP Tunnel--->|
>   |                               |
>   |<---------PPP Session--------->|
>   |                               |
> 
> The peer first negotiates PPP-LCP with the LAC; then LAC
> negotiates the EAP with the Peer (or acts as a paas-thru);
> As an outcome of the successful authentication, the LAC
> tunnels PPP session to the LNS; and now LNS starts
> negotiating the EAP with the peer;
> 
> Thus, in this case, the peer negotiates EAP/EAP method with
> the LAC; receives the EAP-success followed by the EAP
> request/Identity (or EAP request/auth method) from the LNS.
> 
> I don't think lower layer would initate the multiple
> conversations. The peer has a point to point lower layer,
> hence it would not be able to distinguish if the incoming
> EAP packets are coming from the LAC or LNS. Hence  I was
> wondering if the statemachine is equiped to handle such a
> back to back EAP/EAP method negotiations?
> 
> Thanks
> Mahesh
> 
> --- Pasi.Eronen [at] nokia.com wrote:
> 
> > 
> > Mahesh,
> > 
> > Negotiating the use of EAP and triggering the start of an
> > EAP conversation happens in the lower layer outside EAP, 
> > so it's really beyond the scope of the peer state machine.
> > 
> > But I don't think there's anything in draft-ietf-eap-
> > statemachine that would prevent a lower layer from having 
> > several separate EAP conversations, either in sequence 
> > like (in PANA), or in parallel in which case you need 
> > multiple "instances" of the state machine).
> > 
> > Best regards,
> > Pasi
<snip>