Subject: RE: [mobile-ip] RE: [diameter] DIAMETER support for MIP question

From: "Kuntal Chowdhury" <[email-masked]>
Date: Wed, 3 Oct 2001 17:07:34 -0500

Pat,
Please see my responses inline:

Thanks,
Kuntal

-----Original Message-----
From: Pat Calhoun [mailto:[email-masked]]
Sent: Wednesday, October 03, 2001 11:24 AM
To: [email-masked]
Cc: Pat Calhoun; [email-masked]; [email-masked]
Subject: Re: [mobile-ip] RE: [diameter] DIAMETER support for MIP
question

On Tue, Oct 02, 2001 at 06:23:49PM -0500, Kuntal Chowdhury wrote:
> Pat,
> Thanks for responding. I am still not clear on the following two issues in
> "draft-ietf-aaa-diameter-mobileip-07":
> 
> 1. Section 1.4 Page 12
> 
> AAAF in foreign network 1 will send back error code
> "DIAMETER_ERROR_NO_FOREIGN_HA_SERVICE" to AAAH if foreign network 1 does
not
> wish to provide HA service when the MN has moved to foreign network 2.
> However it is not mentioned when the AAAH receives such an error code from
> AAAF what happens to the mobile IP registration request. 
> I think some text is required to capture this exception case. Options
before
> AAAH is either send another HAR to AAAF in network 2 (only if AAAF had set
> the "Foreign-Home-Agent-Available" flag in AMR), otherwise AAAH may assign
a
> HA in the home network or reject the mobile IP registration request. 

The text that follows is at the end of section 1.4 and I believe it does
cover this error:

"
   If the old Foreign Network does not permit the use of its Home Agent
   when the Mobile Node moves to a new foreign network, the AAAH or AAAF
   MUST return an AMA with the Result-Code AVP set to
   DIAMETER_ERROR_HA_NOT_AVAILABLE. Upon receipt of this error, the
   Foreign Agent MUST issue a Mobile IP Registration Reply to the Mobile
   Node with an appropriate error. The Mobile Node MAY attempt to
   request that a new Home Agent and Address be allocated. When the AAAH
   transmits such an error, it MUST issue a Diameter Abort-Session-
   Request message to the AAAF overseeing the Home Agent to enable it to
   release any resources."

Is this not sufficient?

KC> This text captures one of the three options that I mentioned before. The
three options for AAAH are:

i.	AAAH sends an HAR message to AAAF2 if AAAF2 sets
Foreign-Home-Agent-Available = 1
ii.	AAAH assigns a HA in the home network if (i) = false
iii.  AAAH rejects the registration request if (i) and (ii) = false

The text in the draft covers, only option (iii). 

The advantages of adopting the suggested approach are:
a) MN won't have to initiate another MIP registration request.
b) No need for extra messaging over the air.

> 2. When MN requests for a HA allocation in the foreign network, and for
some
> reason AAAF does not set "Foreign-Home-Agent-Available" or AAAH denies the
> request, how does the MN come to know that it did not get what it
requested?

It would receive the Registration Reply with the proper error code. There
are
a variety of error codes defined in RFC2002, but perhaps a more specific
error
code could be introduced? If so, where should it be specified?

KC> May be we can add this error code in 2002bis.

> If it is immaterial for the MN's MIP client to know where the HA gets
> allocated, why does it ask for it differently e.g. some MNs requesting
with
> 0.0.0.0 and some others requesting with 255.255.255.255?

corporate customers would most likely want an HA in their corporate
networks.
Normal Internet users don't care where the HA resides.

KC> 
If the corporate customers need HAs in their corporate networks, AAAH should
be able to enforce that. Even if all the mobiles send the same indication
for dynamic HA allocation, AAAH should have the ability to decide whether
the HA to be assigned in the home network or in the serving network. e.g.

-----
MN sends 0.0.0.0 in the HA field in RRQ

If AAAF is willing to provide HA service (irrespective of the value in HA
field in RRQ), then it sets flag1 == 1 in AMR
If AAAH policy says "HA must be in the home network" (say for corporate
users) then AAAH assigns HA in the home network 
If AAAH policy says "HA may be in the serving network" (say for normal
internet users) then AAAH sends HAR to AAAF

If AAAF is not willing to provide HA service, then it sets flag1 == 0 in AMR
AAAH assigns HA in the home network (no other choice)
-----

The point that I am trying to make is, MNs don't need to send different
indications to the network, the home network knows user's preferences and
should be able to assign HAs accordingly.

-Kuntal

PatC