Subject: [AAA-WG]: Issue 211: When should Destination-Host be present in HAR?

From: Pat Calhoun <[email-masked]>
Date: Thu, 25 Oct 2001 17:31:10 -0700

Submitter name: Pat Calhoun
Submitter email address: [email-masked] 
Date first submitted: 25-Oct-01 
Reference:  
Document: all
Comment type: Technical 
Priority: 1
Section: 
Rationale/Explanation of issue: 

In the MIP draft, it isn't really clear when the Destination-Host should
be present in the HAR when the HA is assigned in a foreign domain. The
text and figure need to be cleaned up.

---

From: "Bob Kopacz" <[email-masked]>
Date: Tue, 30 Oct 2001 10:37:16 -0500

Hi Pat,

The question that prompted this issue was:

Q1: When first setting up the mobile node's session, if the AAAF has
offered to allocate a HA in the foreign domain and the AAAH has accepted
the AAAF's offer, does the AAAH need to send the HAR to the specific AAAF
which forwarded the AMR, or can the HAR be receive by any old AAA server 
in the foreign network?  The draft is unclear.

From the text and diagrams in the mobile-ip draft, it appears that the
AAAH targets the HAR to the specific AAAF which forwarded the AMR.  All
diagrams show the the HAR going to the AAAF which sent the AMR, and the
text contains phrases like:    

   "... the AAAH sends the HAR message to *the* AAAF ..."

But based on our bakeoff conversations, my understanding now is that the
HAR could be sent to any AAA server in the foreign realm, not
necessarily the one that sent the AMR.  So this initial HAR would
contain a Destination-Realm and not a Destination-Host.

Anyway, whichever way is correct, it would be good to clarify the draft,
as follows (in section 1.4):

"If the HA hasn't yet been allocated by the foreign domain, the HAR sent
by the AAAH back to the foreign realm will not necessarily be received
by the same AAAF which sent the AMR."

or if the above is not true:

"If the HA hasn't yet been allocated by the foreign domain, the HAR sent
by the AAAH back to the foreign realm is sent to the same AAAF which
sent the AMR.  The AAAH must set the value of the HAR's Destination-Host
AVP to the AAAF's DiameterIdentity.  The AAAH determines the AAAF's
DiameterIdentity as follows: If there are two or more Route-Record AVPs
in the AMR, the 2nd Route-Record AVP contains the AAAF's
DiameterIdentity (the 1st Route-Record contains the FA's identity). If
there are fewer than 2 Route-Record AVPs, then the peer which sent the
AMR to the AAAH is the AAAF."

Also, two more questions, 

If this HAR is received and processed by an AAAF2 other than the AAAF1
which sent the AMR:

Q2: If AAAF1 has offered to allocate an HA in the foreign network, how
does he know that AAAF2 can make good on this offer?  AAAF2 may not have
any HAs to talk to.

Q3: If AAAF1 has offered to allocated a HA in the foreign network, he
sends his candiate HA in the new "Candidate-Home-Agent-Host" AVP (issue
#223).  The AAAH's HAR then needs to convey this candidate HA to AAAF2,
and AAAF2 must be able to route to this HA.

Thanks,
Bob K.