Subject: [AAA-WG]: Indication for Home Agent allocation??

From: "Martin Julien (ECE)" <[email-masked]>
Date: Wed, 21 Mar 2001 15:53:01 +0100

Hi,

1. What happens if a MN requests an Home Agent in the Foreign Domain, by setting the address of the Home Agent to 255.255.255.255, and that the AAAF does not allow an HA to be allocated within its Foreign Domain? What error should be returned to MN? Should the AMR reach the AAAH at all? Is it at all possible to reject such a request? Should we use the DIAMETER_ERROR_NO_FOREIGN_HA_SERVICE result-code? If yes, then I guess we need to change its description in section 3.1.

In fact, I'm wondering if that Home Agent set to 255.255.255.255 is only an indication of a preferred location for the HA?, or it is strongly required for the HA to be in the Foreign Domain??? If it is not strongly required, then I'd say that it would be possible to allocate one in the Home Domain, right? I would say that an AAAF should always recommend an HA to be allocated within the Foreign Domain for optimization purposes, by setting the Foreign-Home-Agent-Available flag whenever it supports it, right? In that case, what is the real need for the indication from the MN?

2. What happens if the MN requests an Home Agent by specifying an address different then 0.0.0.0 and 255.255.255.255, if that HA is unknown in the Home Domain and also in the Foreign Domain? There is no result-code for indicating this to the MN, i.e. that the requested HA is bad, similar as the error for a bad Home Address, we might need DIAMETER_ERROR_BAD_HOME_AGENT, right? Unless an HA should be allocated anyway, assuming that it is a different Home Agent address?

Also, the spec says, in section 1.2 page 5 of the Diameter MIP extension -01, that an AMA (now an HAR I guess) must be sent to the AAAF in the case the Home Agent is not known by the AAAH. The thing is that it is not sure yet at this point that the AAAF will necessarily know it either. Then I was wondering if the AAAF should inform that the HA is available by setting the Foreign-Home-Agent-Available flag in the MIP-Feature-Vector AVP, when an HA is specified and it is available locally. That information could be used in the AAAH to be sure that the HA is available as specified in the Home Agent AVP in the Foreign Domain, and allocate a new Home Agent in the Home Domain directly, without asking unnecessarily to the AAAF, if ever it is allowed by the spec to override the Home Agent address when the one sent from the MN is not valid.

Regards,
/Martin

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From: Patrice Calhoun <[email-masked]>
Date: Tue, 27 Mar 2001 07:50:37 -0800 (PST)

Sorry for the latency.... just starting to catch up.

> 1. What happens if a MN requests an Home Agent in the Foreign Domain, by
> setting the address of the Home Agent to 255.255.255.255, and that the AAAF
> does not allow an HA to be allocated within its Foreign Domain? What error
> should be returned to MN? Should the AMR reach the AAAH at all? Is it at all
> possible to reject such a request? Should we use the
> DIAMETER_ERROR_NO_FOREIGN_HA_SERVICE result-code? If yes, then I guess we
> need to change its description in section 3.1.
> 
> In fact, I'm wondering if that Home Agent set to 255.255.255.255 is only an
> indication of a preferred location for the HA?, or it is strongly required
> for the HA to be in the Foreign Domain??? If it is not strongly required,
> then I'd say that it would be possible to allocate one in the Home Domain,
> right? I would say that an AAAF should always recommend an HA to be
> allocated within the Foreign Domain for optimization purposes, by setting
> the Foreign-Home-Agent-Available flag whenever it supports it, right? In
> that case, what is the real need for the indication from the MN?

I think that setting the Home Agent to all ones expresses a preference for
having the HA in the visited network, but only if possible. If the AAAF
decides for some reason that it cannot, or does not want to, allocate
additional resources in the visited network, it forwards the AMR to the AAAH
without the Foreign-Home-Agent-Available bit set.

> 
> 2. What happens if the MN requests an Home Agent by specifying an address
> different then 0.0.0.0 and 255.255.255.255, if that HA is unknown in the
> Home Domain and also in the Foreign Domain? There is no result-code for
> indicating this to the MN, i.e. that the requested HA is bad, similar as the
> error for a bad Home Address, we might need DIAMETER_ERROR_BAD_HOME_AGENT,
> right? Unless an HA should be allocated anyway, assuming that it is a
> different Home Agent address?

ok, well the MN doesn't speak Diameter, so it would have to receive a
Registration Reply with the code set to 136 (unknown home agent address). I
suppose your comment here is more to the fact that there doesn't exist a
Diameter error code to indicate this.

> 
> Also, the spec says, in section 1.2 page 5 of the Diameter MIP extension
> -01, that an AMA (now an HAR I guess) must be sent to the AAAF in the case
> the Home Agent is not known by the AAAH. The thing is that it is not sure
> yet at this point that the AAAF will necessarily know it either. Then I was
> wondering if the AAAF should inform that the HA is available by setting the
> Foreign-Home-Agent-Available flag in the MIP-Feature-Vector AVP, when an HA
> is specified and it is available locally.

Well, that would require less state on the AAAH, which is goodness, and only
requires a small modification (specifying when the flag is to be set in the
AVP).

> That information could be used in
> the AAAH to be sure that the HA is available as specified in the Home Agent
> AVP in the Foreign Domain, and allocate a new Home Agent in the Home Domain
> directly, without asking unnecessarily to the AAAF, if ever it is allowed by
> the spec to override the Home Agent address when the one sent from the MN is
> not valid.
> 

ok, but now that I think of this, the AAAH needs to maintain state as to where
the HA is, because the HA MAY in fact be in a third network, and the AAAF in
that network has no opportunity to twiddle the bit in the vector AVP.

So, I guess I am saying that the above would only work for one of two cases,
and therefore is not that useful.

PatC

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From: Michael Chen <[email-masked]>
Date: Tue, 27 Mar 2001 10:10:55 -0800

Pat,

Correct me if I am wrong.
If Mobile_Node_Address  is NULL(0.0.0.0) it request a home address.
If Home_Agent_Address  is NULL(0.0.0.0) MN is willing Home Agent alocate in visit
domain.
If Home_Agent_Address  is -1(255.255.255.255) Home Agent MUST alocate in home
domain
What they describe in session 4.7 MIP-Feature-Vector AVP in diameter_mobileip_01
is not correct.
Home address is differ from "home agent" address. This term confuse reader and
some "home address" which is not correct in the draft need change to "home agent
address". I would suggest you to use "mobile node address" instead of home
address.

Michael

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From: Patrice Calhoun <[email-masked]>
Date: Tue, 27 Mar 2001 10:35:22 -0800 (PST)

> If Home_Agent_Address  is NULL(0.0.0.0) MN is willing Home Agent alocate in
> visit domain.
> domain What they describe in session 4.7 MIP-Feature-Vector AVP in
> diameter_mobileip_01 is not correct.
> Home address is differ from "home agent" address. This term confuse reader
> and some "home address" which is not correct in the draft need change to
> "home agent address". I would suggest you to use "mobile node address"
> instead of home address.

That sounds about right. I'll have a look at -02 and see what it says. 

PatC