Subject: [Pana] Another issue in draft-ietf-pana-statemachine-00

From: Sasikanth Bharadwaj <[email-masked]>
Date: Thu, 07 Jul 2005 11:40:47 +0530

Hi

This looks like an issue to me in the PaC state machine

In WAIT_EAP_MSG State

EAP_RESP_TIMEOUT         if (key_available())       WAIT_PAA
                              PAN.insert_avp("MAC");
                            PAN.S_flag=PAR.S_flag;
                            PAN.N_flag=PAR.N_flag;
                            Tx:PAN();The PAN goes without EAP payload when
EAP_RESP_TIMEOUT occurs. Whenthe EAP_RESPONSE event occurs, the PaC is in
the WAIT_PAA state whichdoes not handle this event. The PAA receives the PAN
and waits for thePAR which never comes. Think this event has to be handled
in theWAIT_PAA stateThanksSasikanth

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From: Sasikanth Bharadwaj <[email-masked]>
Date: Fri, 08 Jul 2005 11:20:37 +0530

Hi

> >
> I think it migth be better if we don't handle EAP_RESP_TIMEOUT in 
> WAIT_PAA for the following reasons:
> 
> 1. The PANA fsm should only anticipate any EAP events and interaction 
> within WAIT_EAP_MSG or other PANA-EAP interface states. Adding EAP 
> interface events on states where the PANA FSM is not expecting any EAP 
> interaction creates overly complex fsm and breaks the syncrhonicity of 
> the protocol. Imagine trying to send a PAN when handling 
> EAP_RESP_TIMEOUT in WAIT_PAA when your actually waiting for the PAR ...
> 
> 2. In the scenario stated above, if EAP_RESP_TIMEOUT occurs and the PaC 
> sends an PAN without an EAP payload then the EAP fsm on the PAA should 
> re-transmitt the last EAP request and hopefully the EAP fsm on the PaC 
> will respond before EAP_RESP_TIMEOUT. If the EAP fsm on the PaC always 
> responds after an EAP_RESP_TIMEOUT then there must be something wrong 
> with the implementation :) ....
> 
> 3. In your scenario, you mentioned the PAA receives the PAN and waits 
> for the PAR. As noted in (2), the PAA should use a new PAR when the EAP 
> fsm retransmitts the EAP request.
> 
There seems to be another problem here
Say the EAP fsm times out and retransmits the earlier request
The PAA fsm is in the WAIT_PAN_OR_PAR state at that time
and this state does not handle the EAP_REQUEST event so there's 
actually no way a new PAR gets generated here. I guess this will eventually
result in an EAP_TIMEOUT event which will terminate the session.
I feel  EAP_REQUEST has to be handled in WAIT_PAN_OR_PAR state
at the PAA or state should not be changed at the PaC when
EAP_RESP_TIMEOUT occurs in WAIT_EAP_MSG state.
That would be consistent with what you said about anticipating EAP events
because the next event has to be an EAP_RESPONSE event and we should
be in the WAIT_EAP_MSG state to handle that

> regards,
> -- victor fajardo
Regards

Sasikanth

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From: Victor Fajardo <[email-masked]>
Date: Fri, 08 Jul 2005 09:10:38 -0400

Comments below.

>be in the WAIT_EAP_MSG state to handle that
Good point. Though i think we are also missing the fact that the PAR is 
retransmitted from the PAA in this scenario. So the current EAP request 
will still be sent to the PaC even if the PAA is in WAIT_PAN_OR_PAR. 
Therefore, I retract my previous comments regarding EAP fsm 
retransmission and instead we should rely on PANA retransmission. What 
do you think ?

This also brings to mind another question, we don't seem to handle EAP 
re-transmission in the PANA fsm. Should we consider this or rely solely 
on PANA retransmissions ? Maybe this has been discussions about this 
before ....

-- victor

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From: Yoshihiro Ohba <[email-masked]>
Date: Fri, 08 Jul 2005 00:24:28 -0400

Sasi,

An implemetation can queue the EAP-Response generated by EAP peer FSM.
Then, an EAP_RESP_TIMEOUT event can be generated later, depending on
whether there is a queued EAP-Response, when the FSM enters a state
that deals with the event.

Does this make sense?

Yoshihiro Ohba

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From: Sasikanth Bharadwaj <[email-masked]>
Date: Sat, 09 Jul 2005 14:10:02 +0530

----- Original Message ----- 
From: "Victor Fajardo" <[email-masked]>
To: "Sasikanth Bharadwaj" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, July 08, 2005 6:40 PM
Subject: Re: [Pana] Another issue in draft-ietf-pana-statemachine-00

> will still be sent to the PaC even if the PAA is in WAIT_PAN_OR_PAR.

Even the current PAR will not be retransmitted because the PAA has received
a PAN for the PAR it has sent. The situation is effectively a deadlock
because
the PAA keeps waiting for the PAR that never arrives

> on PANA retransmissions ? Maybe this has been discussions about this
I think handling EAP retransmission would help in solving this particular
issue
but Im not sure whether it would result in some other complexities.

regards
Sasikanth

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From: Sasikanth Bharadwaj <[email-masked]>
Date: Sat, 09 Jul 2005 14:14:23 +0530

Hi Yoshi

> that deals with the event.
I really didn't get what you are trying to suggest
can you elaborate?
As per the draft, EAP_RESP_TIMEOUT is generated when
EAP request is given to the EAP peer but the response is not
received in a given period
I dont know what you meant when you said this event can be
generated later

regards

Sasikanth

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From: Victor Fajardo <[email-masked]>
Date: Sat, 09 Jul 2005 18:31:22 -0400

Hi,

>>>actually no way a new PAR gets generated here. I guess this will
>>>      
>>>
>eventually
>  
>
Your correct. Then I'm convinced and we should add an EAP_REQUEST in
WAIT_PAN_OR_PAR at least to handle EAP retransmission in the scenario
you stated to break the known deadlock. In other cases where EAP
retransmission events migth occur, I'm currently proposing that the PANA
fsm can leave it as implementation issue, i.e. implementation may queue
EAP messages as Ohba suggested or maybe ignore it. Is this ok with you ?

-- victor

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From: Yoshihiro Ohba <[email-masked]>
Date: Sun, 10 Jul 2005 01:13:45 -0400

> I dont know what you meant when you said this event can be

Sorry, I meant EAP_RESPONSE event in my comment.

Yoshihiro Ohba

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From: Sasikanth Bharadwaj <[email-masked]>
Date: Mon, 11 Jul 2005 11:11:18 +0530

Hi

> EAP messages as Ohba suggested or maybe ignore it. Is this ok with you ?

That is fine

Sasikanth

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From: Victor Fajardo <[email-masked]>
Date: Mon, 11 Jul 2005 08:33:31 -0400

If there are no more comments on the pana fsm, I'll submit the next 
version of the draft early this week.

thanks,
-- victor