Subject: [AAA-WG]: MIP-Feature-Vector should decide

From: Johan Johansson <[email-masked]>
Date: Tue, 13 Nov 2001 13:07:32 +0100

All,

I have some concerns after reading pages 6 and 7 of the mip-alpha2 
draft. Please forgive me if this has already been dealt with.

Why isn't the feature vector *the* authority on whether ip addresses and 
home agents should be allocated? For instance

"In the event the AAAH handles address allocation, it includes it in a 
MIP-Mobile-Node-Address AVP within the HAR. The absence of this AVP 
informs the Home Agent to perform the allocation."

"If no Home Agent was specified, and if the MIP-Feature-Vector has the 
Home-Agent-Requested flag set ... the AAAH SHOULD allocate a home agent..."

Wouldn't it be cleaner if the feature vector *dictated* what was to be done?

j

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From: Pat Calhoun <[email-masked]>
Date: Tue, 13 Nov 2001 09:24:16 -0800

So you are stating that the AAAH should change the MIP-Feature-Vector instead?
Of course, if this was the case, when the HA were to send the AVP in the
accounting messages, the fact that an address was allocated would be lost.

So I think the way the protocol is current designed provides this
information in accounting records.

PatC

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From: "Fredrik Johansson" <[email-masked]>
Date: Tue, 13 Nov 2001 18:17:37 +0100

Now I don't understand what you mean, what avp do you refer to in the
accounting message, the MIP-feature-vector or the MIP-Mobile-Node-Address
AVP?

Anyway, what function does the mip-feature-vector serve in an accounting
message? An accounting message doesn't make sence unless an ip address has
been assigned, thus it should be enough to send the MIP-Mobile-Node-Address
AVP in the ACR,

or have I missed something?

What I believe Johan is saying is that AAAh will only change the
mip-feature-vector if it assigns an ip address to the mobile node. Thus the
HA can look at the mip feature vector to decide if an ipaddress should be
assigned, in the same way as the AAAh does when it decides if an ip address
should be assigned.

/Fredrik

>-----Original Message-----
>From: Pat Calhoun [mailto:[email-masked]]
>Sent: den 13 november 2001 18:24
>To: Johan Johansson
>Cc: aaa-wg
>Subject: Re: [AAA-WG]: MIP-Feature-Vector should decide
>
>

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From: "Bob Kopacz" <[email-masked]>
Date: Tue, 13 Nov 2001 15:08:25 -0500

> message? 

Whatever function it serves, if the FA and HA both generate accounting for
the same subsession, the FA and HA can send different values for the
MIP-Feature-Vector in their ACRs.

This is because the AAAF can modify the MIP-Feature-Vector which
the FA sends in the AMR, and the FA isn't privy to the changes, 
so the FA's image of the MIP-Feature-Vector won't necessarily match 
the HA's (updated) image of the MIP-Feature-Vector.

---

From: Johan Johansson <[email-masked]>
Date: Wed, 14 Nov 2001 01:23:41 +0100

I am still not entirely sure what Pat's mail ment, which probably just 
goes to show that I should go read the accounting sections instead of 
potentially confusing other people, but it seems to me that if 
accounting is based on the Mip-Feature-Vector that is an argument *for* 
making it the dictator and not against it.

j

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From: Johan Johansson <[email-masked]>
Date: Wed, 14 Nov 2001 01:43:21 +0100

Ah, now I think I understand what you mean. Just to make sure, I guess 
you mean the case where a home agent is requested and the AAAH *does* 
allocate it. According to my suggestion this would then mean that the 
AAAH would clear the Mobile-Node-Home-Address-Requested bit, which would 
then be unknown to the HA.

I'll go read the accounting parts carefully and either perform a 
self-reject on this "issue" or try to come up with a convincing argument 
tomorrow morning.

j

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From: Pat Calhoun <[email-masked]>
Date: Tue, 13 Nov 2001 20:03:45 -0800

Let me try again. The MIP-Feature-Vector is included in the Accounting
messages as an indication of the type of services provided (e.g. HA in
foreign domain, dynamic HA, dynamic home address). If the AAAH changes the
feature vector prior to sending it to the HA, which in turn includes this
AVP in the accounting messages, then this information is lost.

Of course, we could have the HA create yet another AVP, but I honestly don't
see both the need, and why the current protocol isn't correct.

PatC

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From: Johan Johansson <[email-masked]>
Date: Wed, 14 Nov 2001 22:51:27 +0100

>AVP in the accounting messages, then this information is lost.
Since accounting messages are not necessarily sent to the AAAH the 
information could indeed be lost. The AAAH can't necessarily even find 
out where the HA will send it, so there is little hope of even finding 
an arbitrarily ugly patch. As usual, feel free to point out my 
misconceptions.

>see both the need, and why the current protocol isn't correct.
I never ment that it was not *correct*, I was merely exploring a 
possibility to make the protocol simpler and clearer, but it does seem 
to render the protocol broken.

j