Subject: [mobile-ip] Requested changes in RFC3220

From: "Kuntal Chowdhury"<[email-masked]>
Date: Fri, 24 May 2002 11:28:52 -0500

Hi all,
Sometime ago we had an email discussion on processing of RRQ at the HA and
the possible fields in the RRP. The result of the email discussion was some
"proposed text" for the updated version of RFC3220 (RFC3220bis). I have
tried to capture the proposed text below (paragraph 5 of section 3.8.3.2).
We also added an additional restriction in the 4th paragraph of section
3.8.3.2 of RFC 3220. I have exchanged email with Charlie and we are in
agreement with these changes in this section. Please review and comment if
necessary.

The changes are in the 4th and the 5th paragraph of section 3.8.3.2.

"
3.8.3.2. Registration Reply Fields

   ......

   If the Home Address field of the Registration Request is nonzero, it
   MUST be copied into the Home Address field of the Registration Reply
   message. If the non-zero unicast address in the Home Address field
   does not belong to the subnet of the Home Agent, then the Home Agent
   MUST reject the registration with an error code of 130. Otherwise ...

   If the Home Agent field in the Registration Request contains a
   unicast address of this home agent, then that field MUST be
   copied into the Home Agent field of the Registration Reply.
   Otherwise, the home agent MUST set the Home Agent field in the
   Registration Reply to its unicast address. In this latter case,
   if the destination IP address of the Registration Request is the
   unicast IP address of this Home Agent, the Home Agent MAY accept
   the Registration Request. If the destination IP address of the
   Registration Request is not the unicast IP address of this Home
   Agent, the home agent MUST reject the Registration Request with
   a suitable code(e.g., Code 136) to prevent the mobile node from
   possibly being simultaneously registered with two or more Home
   Agents.
"

Regards,
Kuntal

---

From: Samita Chakrabarti <[email-masked]>
Date: Fri, 24 May 2002 12:55:02 -0700 (PDT)

> "proposed text" for the updated version of RFC3220 (RFC3220bis). I have

There have been discussion in mailing list regarding the dst IP-address
of regReply from the Foreign agent to the mobile node.
As per Charlie's request, I have run by the proposed text for
section 3.7.2.3 twice in this list. I understand your proposed text is for
the home-agent reply field.

>    MUST reject the registration with an error code of 130. Otherwise ...

I think this is too restricitve check and will break some implementations.

In the deployment scenario, a home-agent may support mobile nodes that
are never home and they are always roaming (cell phones). In most cases,
they use private-addresses for which home-agent doesn't have a particular
subnet, but home-agent allocates those private addresses to it's subscribed
MNs, and keep track of them through it's database. 

So, those deployment and implementations will break if you put MUST there.
Actually, I don't see a need for any change in the draft for this purpose. 
  
>    possibly being simultaneously registered with two or more Home

This paragraph looks fine.

Cheers,
-Samita

---

From: "Kuntal Chowdhury"<[email-masked]>
Date: Fri, 24 May 2002 16:10:52 -0500

Samita,
Yes, the proposed text applies to registration reply from the Home Agent.

>    MUST reject the registration with an error code of 130. Otherwise ...

I think the mobile nodes that are never home (always roaming) can be
something
other than cell phones, but that is not the point. The intent of the
proposed
change is to ensure that the mobile node has a way to determine whether it
is on
it's home subnet. When the mobile node requests for a nonzero unicast IP
address 
as it's Home Address and the registration is successful then it knows that
it is 
on it's home subnet. If the registration fails, then it should request for a

dynamic Home Address perhaps with dynamic Home Agent assignment in the 
RRQ. 
However I see your point about private address support. Would you be
agreeable 
if we change the text like this:

"    If the Home Address field of the Registration Request is nonzero, it
     MUST be copied into the Home Address field of the Registration Reply
     message. If the Home Agent cannot support the nonzero unicast address
     in the Home Address field of the Registration Request, then the Home 
     Agent MUST reject the registration with an error code of 129. Otherwise

     ...... 
"

Regards,
Kuntal

  

Cheers,
-Samita

---

From: Samita Chakrabarti <[email-masked]>
Date: Fri, 24 May 2002 16:54:19 -0700 (PDT)

>      Agent MUST reject the registration with an error code of 129. Otherwise

This looks better to me. Thanks.

-Samita