Subject: RE: [seamoby] proactive and reactive CT definitions

From: Nakhjiri Madjid-MNAKHJI1 <[email-masked]>
Date: Mon, 25 Jun 2001 13:55:57 -0500

Hi Charlie,

I guess, I have a question, why would CT have any impact on DAD?
I don't recall of any restrictions on CT that would impact DAD.

Regards,
Madjid

-----Original Message-----
From: Charles E. Perkins [mailto:[email-masked]]
Sent: Thursday, June 21, 2001 5:13 PM
To: Singh Ajoy-ASINGH1
Cc: [email-masked]
Subject: Re: [seamoby] proactive and reactive CT definitions

Singh Ajoy-ASINGH1 wrote:

> Rajeev: While I don't necessarily agree with the example, we all want
> CT to finish before the packets start arriving. That's why we have
> predictive handovers. When you can't do such a thing, e.g., consider
> that link-layer triggers don't work because the two technologies are
> different, you have the initiation of reactive CT after the MN
> establishes a new link.

It is possible or even likely that some packets could be delivered
to the mobile node before the context is transferred, especially
in the reactive case but not necessarily only there.  For example,
given proactive, what if the mobile node starts doing DAD at the
new access router before the context transfer completes?  This would
be quite possible, and I would hate to see the context transfer
protocol place any restrictions otherwise.  Obviously, if DAD is
needed, it would be silly to delay its initiation, even for
proactive.  If, instead, you want to make the definition that
this isn't "pro-active enough", then I would claim that the need
for redefinition exhibits the problem with even the general thrust
of the existing definitions.

> Ajoy: I thought some more about inter-technolgy CT. It seems
> the inter-technolgy CT may be difficult to realize. For
> example, one access network might use PPP while others
> might not. In this case, will it make
> sense to transfer the PPP context from one access router to
> other? Additionally, I think most of us agree that make before
> break handover is possible in inter-technolgy case, when
> some overlap is available between coverage area of
> different technolgies. So Can't
> MN re-negotiate CT with new AR before breaking
> connection with oldAR ?

Sure this can happen, but if inter-technology context transfer is
is available and it saves time, then we should allow it.  The
benefit will be better customer experience in more cases.  Furthermore,
I can't see any downside on the protocol design.  It doesn't seem to
make the problem harder or easier.  And I would hate to see PPP context
become the defining example for context transfer.

Regards,
Charlie P.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 25 Jun 2001 12:06:23 -0700

Hello Madjid,

> I don't recall of any restrictions on CT that would impact DAD.

This was exactly my point.  I suggested that we should allow for
systems in which context transfer can proceed independently from
DAD.  One can imagine protocol restrictions that would enforce a
sequence whereby DAD has to complete before context transfer could
be initiated.  I would like to make sure that such restrictions do
not come into being.  Some people may wish to design systems that
have the restriction, but the general [seamoby] protocol specification
should not mandate any such restriction.

Regards,
Charlie P.