Subject: RE: [mobile-ip] MN that accepts Home Address Allocation

From: "Ahmad Muhanna" <[email-masked]>
Date: Wed, 2 Oct 2002 12:26:17 -0500

Hi Siva,
This is only true in the case when the Mobile Node is trying to establish
a Static Mobile IP call. In other words, the Home Address of the RRQ message
is not 0.0.0.0. and consequently the Home address in the RRP message is not
0.0.0.0.

However, if the Home address in the RRQ message was 0.0.0.0. then
the FA SHOULD set the destination IP address to 255.255.255.255. 
"BROADCAST"

see the same section 3.7.2.3 in RFC 3344 (3220)

      IP Destination Address

               If the Registration Reply is generated by the Foreign
               Agent in order to reject a mobile node's Registration
               Request, and the Registration Request contains a Home
               Address which is not 0.0.0.0, then the IP Destination
               Address is copied from the Home Address field of the
               Registration Request.  Otherwise, if the Registration
               Reply is received from the Home Agent, and contains a
               Home Address which is not 0.0.0.0, then the IP
               Destination Address is copied from the Home Address field
               of the Registration Reply.  Otherwise, the IP Destination
               Address of the Registration Reply is set to be
               255.255.255.255.

Regards,
Ahmad Muhanna

> -----Original Message-----
> From: Sivasundar Ramamurthy [mailto:[email-masked]] 
> Sent: Tuesday, October 01, 2002 4:37 PM
> To: Mobile IP Working Group
> Subject: [mobile-ip] MN that accepts Home Address Allocation
> 
> 
> 
> Hello,
> 
> I was wondering if there are any MN implementations available 
> that can learn its home address allocated in registration 
> replies forwarded by the FA in accordance to 3.7.2.3 in RFC 
> 3220? Per this section, the FA sets the IP dest of the 
> forwarded reply to the home address in the reply received 
> from the HA (the allocated nonzero address).
> 
> Thanks in advance.
> 
> 
> Regards,
> 
> Siva
> 
>

---

From: Sivasundar Ramamurthy <[email-masked]>
Date: Wed, 2 Oct 2002 11:02:11 -0700 (PDT)

Hi Ahmad,

> the FA SHOULD set the destination IP address to 255.255.255.255. 

ah! But that does not seem like the case always. I interpret section
3.7.2.3 like below.

If the RRQ is rejected by the FA, the FA sends the reply to the
255.255.255.255 if the home address is 0.0.0.0. (agree)

If the MN requests a home address (0.0.0.0 in RRQ), and the home
address in RRP from the HA does not contain an allocated address (is
0.0.0.0), the the FA forward the reply to IP dest 255.255.255.255.
(agree)

But if the MN requests a home address (0.0.0.0 in RRQ), and the home
address in RRP from the HA does contain an allocated address (not
0.0.0.0), then the FA forwards the reply to IP dest = allocated
address. (disagree!).

This is from my interpration of this specific sentence, in the context
of the paragraph it is contained in (attached below).

>                Otherwise, if the Registration
>                of the Registration Reply.  

Am I going wrong somewhere?

Regards,

Siva

---

From: Joe Lau <[email-masked]>
Date: Wed, 2 Oct 2002 11:15:21 -0700 (PDT)

I think the text on the RFC is confusing, to say the least. 

It needs to clarify what the IP Dest of the reply be when the
home address field in the reply is allocated by the HA.  It 
should not be copied from the home address filed in the reply
because the MN had no idea what the allocated home address is
to "catch" the reply.

Joe Lau

---

From: "Charles E. Perkins" <[email-masked]>
Date: Wed, 02 Oct 2002 12:51:09 -0700

Hello Joe,

> I think the text on the RFC is confusing, to say the least.

After reading my comment below, I hope you'll be able to
suggest something to make it clearer.

> because the MN had no idea what the allocated home address is

It's true that the MN can't catch the Registration Reply based
on the home address field in that case, but your conclusion does
not follow.  For one thing, the mobile node could not use the
IP field at all for that purpose, no matter what address was
there.  For another thing, the packet will be framed by using
a MAC address that the mobile node CAN recognize.

So, we might as well use the new home address in this case.
It doesn't hurt.

Regards,
Charlie P.

---

From: Joe Lau <[email-masked]>
Date: Wed, 2 Oct 2002 14:04:00 -0700 (PDT)

Hello Charlie,
  
> So, we might as well use the new home address in this case.

Your logic makes sense to me.  However, there are two persons out there
(Siva and Ahmad) have different interpretations of the text.  I think 
some clarification should be done to the text.  

What about this (stuffs in (...) ):

      IP Destination Address

               If the Registration Reply is generated by the Foreign
               Agent in order to reject a mobile node's Registration
               Request, and the Registration Request contains a Home
               Address which is not 0.0.0.0, then the IP Destination
               Address is copied from the Home Address field of the
               Registration Request.  Otherwise, if the Registration
               Reply is received from the Home Agent, and contains a
               Home Address which is not 0.0.0.0 (either the same as
	       that on the original Registration Request or dyanamically 
               alocated by the Home Agent), then the IP Destination Address 
               is copied from the Home Address field of the Registration 
               Reply.  Otherwise, the IP Destination Address of the 
               Registration Reply is set to be 255.255.255.255.

Or whatever text added that will make the interpretation easier and clearer.

Regards,

Joe Lau

---

From: Bjorn Andersson <[email-masked]>
Date: Thu, 3 Oct 2002 10:22:36 +0300

> Or whatever text added that will make the interpretation easier and clearer.

I think the text could be still clearer and shorter since what
the text is actually saying is that "if the Home Address in the
Registration Reply is 0.0.0.0 then the IP Destination Address of
the Registration Reply is set to be 255.255.255.255, otherwise the
IP Destination Address is copied from the Home Address field of the
Registration Reply."  This is true in any case independent of whether
the Reply is generated by the FA or HA.

  Bjorn

-- 
Bjorn Andersson <[email-masked]>                       +358 50 341 2556
Lifix Systems Oy <http://www.lifix.fi/>                 PGP id 5AFC144B
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