Subject: [Mip4] A comment on draft-kulkarni-mobileip-dynamic-assignment-02

From: Yoshiyuki Tsuda <[email-masked]>
Date: Fri, 21 Nov 2003 00:09:13 -0800

Hello, the authors and all,

 I've found there are two more possible scenarios where an
 assigned HA can initiate a redirection of a binding to another
 HA between registrations.  That is:

 Scenario-A) If there is a group of HAs, an assigned HA will
 be anchored at the 1st registration. But, due to load balance or
 so on, the assigned HA may want to redirect a specific binding
 to another HA in the meantime of registrations by sending a
 registration reply with
 - the error code of REDIRECT-HA-REQ and
 - Redirected HA address extension.
 After receiving the above registration reply, an MN can send
 a registration request to the redirected HA.

 Scenrio-B) If there are an active HA and a standby HA, and if
 the active HA fails, the standby HA can take over the role by
 sending registration replies, like the above, to all binding MNs.

 Are the above scenarios acceptable ?

Thanks in advance.
-Yoshi

-- 
Mip4 mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/mip4

---

From: Henrik Levkowetz <[email-masked]>
Date: Fri, 21 Nov 2003 12:44:12 +0100

Hi Yoshi,

>  a registration request to the redirected HA.

This scenario seems to me a straightforward application of the
dynamic HA-assignment draft.

>  sending registration replies, like the above, to all binding MNs.

This scenario would _not_ (if I understand you correctly) be
handled by the mechanism in the HA-assignment draft, but is exactly
one of the scenarios which would be handled by an upcoming HA-re-assignment
draft I'm writing.

	Best regards,
		Henrik

---

From: Milind Kulkarni <[email-masked]>
Date: Fri, 21 Nov 2003 11:01:51 -0800

Yoshi,

Please see below...

>  a registration request to the redirected HA.

If this is initial registration request, then the draft takes
care of this exactly as pointed by Henrik.

If you mean transferring the bindings in the middle of
the session, it is a different problem and hence out of scope
of the draft.

>  sending registration replies, like the above, to all binding MNs.

I assume there is 1:1 HA redundancy. In such case the standby
HA will take over, without Mobile IP getting involved. The
redundancy protocol should transparently handle switchovers
without Dynamic HA assignment getting involved.

Milind

---

From: Yoshiyuki Tsuda <[email-masked]>
Date: Fri, 21 Nov 2003 13:12:09 -0800

>the session, it is a different problem and hence out of scope

 OK. I understood it was out of scope.  I think, the only problem
 about my scenario is a binding termination by an HA in the middle
 of session.  Are there any other problems in such a scenario ?

>without Dynamic HA assignment getting involved.

 OK.  This scenario is also out of scope.  I'd like to wait for
 Henrik's coming I-D, and discuss there.

Thank you.
-Yoshi

---

From: Yoshiyuki Tsuda <[email-masked]>
Date: Fri, 21 Nov 2003 13:11:57 -0800

Hi Henrik,

 Thank you for your email.  My comments are inlined:

>dynamic HA-assignment draft.

 Which do you assume "at the 1st registration" or "in the middle of
 session" ?
 If you assumed at the 1st registration, I agree this scenario is a
 straightforward application.  But, I meant in the middle of
 session.  As Milind pointed out in his email, it seems to be out
 of scope of the current dynamic HA I-D.  I think, the only
 problem of this scenario is a binding termination in the middle
 of session by HA, although I believe it is acceptable to an MN.

>one of the scenarios which would be handled by an upcoming HA-re-assignment

 OK.  I'm looking forward to seeing your new I-D. :)
 Have a nice weekend!

Best regards.
-Yoshi

---

From: Henrik Levkowetz <[email-masked]>
Date: Sat, 22 Nov 2003 13:39:18 +0100

>  Which do you assume "at the 1st registration" or "in the middle of

I ment at the 1st registration.

>  of scope of the current dynamic HA I-D.  
>
>  I think, the only

Possibly this could be made to work. But there would have to be
a bit more text in the draft to describe this scenario, then; 
additionally it seems to be a bit at odds with the base premise
of this draft. We probably should think a bit about this, whether
we should extend the dynamic HA assignment draft in this direction,
or whether we should put it in the HA re-assignment draft.

What do other folks think?

	Henrik

---

From: Henrik Levkowetz <[email-masked]>
Date: Sat, 22 Nov 2003 13:55:11 +0100

> without Dynamic HA assignment getting involved.

This assumes use of something like VRRP or CARP, with additional
add-ons to take care of synchronization of MIP registrations
between the 2 HA's. As VRRP isn't IPR free, this has been a bit
of a problem to some HA providers. Now that CARP is becoming
available, this way of handling it may become more interesting,
though.

	Henrik

---

From: Milind Kulkarni <[email-masked]>
Date: Tue, 25 Nov 2003 10:24:48 -0800

Henrik, Yoshi,

Please see inline....

> or whether we should put it in the HA re-assignment draft.

Following up on this thread, I am not sure what you have
in mind. Is it (a) HA re-assignment in the middle of the
session where session can be terminated or (b) HA re-assignment
in the session where the session remains un-interrupted?

If it's (a), then I think it's easy to extend the current
Dynamic HA assignment draft.

Thanks,
Milind

---

From: Henrik Levkowetz <[email-masked]>
Date: Tue, 25 Nov 2003 21:45:26 +0100

> Henrik Levkowetz wrote:
[...]
> Dynamic HA assignment draft.

Actually, I think (a) would be rather bad. I don't think we
should go there, personally.

(b) should be covered by the HA re-assignment drafts, rather
than this one -- the solutions have different focus, are 
useful in different scenarios, and don't really overlap,
I think.

	Regards,
		Henrik

---

From: Milind Kulkarni <[email-masked]>
Date: Tue, 25 Nov 2003 14:11:36 -0800

> should go there, personally.

I agree this is not the path to go. However, I am interested
in knowing your reasons why you think it's bad, other than
obvious session termination.

> useful in different scenarios, and don't really overlap,

I agree completly.

Milind

---

From: Henrik Levkowetz <[email-masked]>
Date: Tue, 25 Nov 2003 23:33:07 +0100

Hi Milind,

> obvious session termination.

- The obvious session termination :-)

	Henrik

---

From: Yoshiyuki Tsuda <[email-masked]>
Date: Tue, 25 Nov 2003 23:50:52 -0800

Hi Henrik and Milind,

 My comment is at the bottom...

>- The obvious session termination :-)

 The session can be continued, if a next HA is assigned in the
 same subnet with the previous HA, and if the same home
 address is assigned.
 But, additional spec is required.  Without an additional spec,
 an MN cannot receive a registration reply (RRP) because of
 an ID mismatch error, if an RRP is received without sending
 a registration request.  I was afraid this kind of additional spec
 might be bad...

Thanks.
-Yoshi

---

From: Henrik Levkowetz <[email-masked]>
Date: Wed, 26 Nov 2003 11:29:27 +0100

Hi Yoshi,

Tuesday 25 November 2003, Yoshiyuki wrote:

[...]
>  a registration request.  I was afraid this kind of additional spec

As I mentioned earlier, I think in this case it should be handled in the
upcoming HA re-assignment draft, rather than in this draft. I'm working
on it, but I'm afraid it'll be a few weeks yet before I can submit. Can
you wait?

	Henrik

---

From: Yoshiyuki Tsuda <[email-masked]>
Date: Wed, 26 Nov 2003 12:25:37 -0800

Hi Henrik,

>on it, but I'm afraid it'll be a few weeks yet before I can submit. Can

 No problem.  I'm looking forward to it.  Please, be sure to make
 some differences with the RO and binding-update I-Ds.  Have a
 nice thanks-giving day!

Thanks.
- Yoshi