Subject: RE: [mobile-ip] Handover Smoothing - What to Do?

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Fri, 27 Jul 2001 16:24:59 +0200

> There is a huge difference between putting "MAY" into
> the fast handover draft, and putting it in a separate
> draft entirely.
> 
> If it's in the fast handover draft, we have to try to get
> it right before the fast handover draft can be finished.
> 
> If it's in another draft, we can work on that draft
> later, which is in my opinion much more appropriate.
> 
	=> I appreciate your logic, but, I believe whatever we do the 
	solution has to be good enough to meet our initial targets. In this case 
	there are two issues:

	- We've introduced a new concept in the v6 draft (and 
	the v4 one) and that is anticipation. This can have 
	negative impacts if not treated carefully. Right now it 
	isn't treated carefully in the v6 draft so I don't believe
	the draft can go ahead with a gap in it because some 
	of us are not sure about the fix. I say we wait until we're
	sure. Anyway the FMIPv6 draft will not become an RFC before
	MIPv6 I hope. So what are we so rushed for ?

	- A solution for the problem has been around for nearly 
	2 years. How much more time is needed ? We don't 
	need every single one to set up experiments. This rule was never
	followed in other drafts. Many people are accepting 
	the approach and it is suggested as an option. 
	Furthermore, the option is already in RFC2002 for 
	MIPv4 why is v6 any different ?
	I think we should be consistent with this because there is 
	nothing v6 specific here.

> I would appreciate taking it out of the IPv4 draft,
> but I haven't had time to study that document so I
> have not made any comments.
> 
	=> Sure. I look forward to your comments, but the question
	on the agenda will be whether the draft should go for last
	call and I sincerely hope that we don't have an answer
	like " this needs further study" (I'm not referring to you but a general comment).
	 We need something concrete as to whether a solution is
	good or bad and why.

	Finally, as I tried to convey many times on the list, the 
	energy wasted in discussing which document this 
	should go in can be better used to identify whether 
	a solution is good enough (for any document) or 
	not. Deciding which doc it should go in is not 
	important now if we can't agree on whether a solution
	is good enough or not. 
	I hope folks would try to concentrate on getting some 
	agreement on this important issue first. 

	Regards,
	Hesham

> "Hesham Soliman (ERA)" wrote:
> > 
> > James, Rajeev and all,
> > 
> > IMHO there is absolutely no gain or benefit in discussing whether
> > smoothing should be in draft X or Y. The question was do we want
> > the bicasting technique or not ? putting it in the right draft is
> > something secodary that will not add value to this discussion.
> > 
> > It seems like some people are saying we don't care as long as you
> > keep it out of this draft !! what's the point of this argument ?
> > Putting it as MAY (as it is in the MIPv4 draft) will have the same
> > effect.
> > 
> > Hesham

---

From: "Charles E. Perkins" <[email-masked]>
Date: Fri, 27 Jul 2001 08:51:19 -0700

Hello again Hesham,

>         MIPv6 I hope. So what are we so rushed for ?

I agree that there isn't a big timing issue until Mobile IPv6
can become Proposed Standard.  As an aside, I've been taught
that it's more appropriate to be specific here, because using
the "RFC status" of a document is highly ambiguous and thus not
directly germane to the issue you raise.

>         nothing v6 specific here.

A lot of solutions have been around for more than two years, and
still not standardized.  That is almost totally irrelevant.
Some of them have engendered dozens or even hundreds (?) of research
papers and many implementations, and still no action by the
working group.  I hope you wouldn't continue to use that as any
relevant criterion.

The existence of the 'S' bit in RFC 2002 has never (to my knowledge)
been tested for interoperability.  My guess is that the same issues
which in my opinion plague bicasting would also plague the use of
the 'S' bit from RFC 2002.  Also, as you have certainly noticed, there
are other features of RFC 2002 which are not present within any
specification for Mobile IPv6.  For instance, there isn't any
Prefix Information option, even though the feature was vehemently
defended for Mobile IPv4.  Thus, I do not believe that your point
about the 'S' bit needs very much consideration.

What is specific about IPv6 is that it has been specified for use
with 3G telephony standards as the appropriate network-layer protocol
and address space.  That makes a lot of things matter in a way that
was not true for IPv4.  In fact, it has motivated a lot of the work
on fast handovers.

We have published work showing that duplicate packets CAN harm
TCP connections if the interference is done systemically, or
if it is done too often.  I still have it as a work item to reconcile
your claims otherwise with our experience.  However, given the volume
of fires that need to be put out right away, not to mention the volume
of mail on these lists (!!), I've been unable to make that study.
So I can only rely on our previous work and my strong intuition to
continue to suggest extreme caution when proceeding to introduce
systemic duplication in IP-based network connectivity.

>         call             ..............

What I might consider to be concrete may still be considered
vague or inconclusive by you or anyone else, and vice versa.

>             Deciding which doc it should go in is not

If a solution isn't good enough, it doesn't belong in any standards-
track document.  If the solution's characteristics are debatable,
then so is its inclusion in the standards document.  In the case of
smoothing techniques the debate can and should proceed independently.

Regards,
Charlie P.

---

From: Pat Calhoun <[email-masked]>
Date: Fri, 27 Jul 2001 09:11:26 -0700

> 	MIPv6 I hope. So what are we so rushed for ?

That fine, but we cannot postpone the low latency v4 draft just because 
the v6 one isn't ready to go.

PatC

---

From: Pat Calhoun <[email-masked]>
Date: Fri, 27 Jul 2001 09:19:35 -0700

> about the 'S' bit needs very much consideration.

In my personal opinion (having been to the interops), most folks hadn't
tested (or even implemented) the 'S' bit because no one knew how it would
ever be used in the real world. I believe that folks now have a reason
for implementing it.

> was not true for IPv4.  In fact, it has motivated a lot of the work

hmmmm..... v4 fast handoff was done prior to the v6 work, so I'm not
sure why you seem to claim that v6 is the one used by telephony standards.
In fact, the cdma2000 folks will be using v4, including Mobile IP, well
before the v6 proponents. 

Perhaps I missed your point.

> systemic duplication in IP-based network connectivity.

Yes, and there are known fixes to the problem you mention. We cannot
live in perpetual darkness just because some folks don't have an OS
with the necessary fix. Let's move forward. People interested in 
fast handoffs will have their stacks fixed.

I, like you, am too busy, but I don't want the work to stall in the
WG until I have the time to catch up.

Thanks,

PatC