Subject: RE: [mobile-ip] RR Last Call Resolution Issue #1 - CLARIFICATION

From: "Alan O'Neill" <[email-masked]>
Date: Thu, 16 May 2002 03:28:32 -0400

Folks,

I hope you don't mind if I make an attempt to try to help clear this one up.

The reaction you are getting Annika is I think because the bandwidth/delay
issues are typically irrelevant. This is because IP networks are fast and
the signalling delays almost always negligible. In addition, the signalling
traffic is a very small portion of the likely throughput for a MN so again,
is irrelevant. Both of these facts are known from existing deployments.
Working hard by deploying a stateful regional box to reduce the signalling
traffic to an even smaller tiny fraction, or to avoid 50ms of delay is
therefore highly questionable...I think people would like you to appreciate
that and hence limit the applicability to cases where the above statements
are not true.

Now the reason I am motivated to have a regional element is mainly because
of commercial decoupling for cellular networks. If MIP is at the basestation
then you have high MIP update rates and the cost of your hand-off, that is
primarily due to inter-FA data forwarding during the hand-off, is minimised.
Unfortunately, if the distant HA is poorly connected or comes up and down as
could easily happen with corporate remote access or small third party stub
networks, then the cost of the operators hand-off is now dependent on that
third party, potentially leading to extended inter-FA forwarding and even
chaining of FA forwarding. The critical point of the regional element here
is that it decouples the reachability/availability of the HA from the
wireless operators local hand-off. The operator hand-off is then dependent
only on elements that they themselves control. In the case of RegTun, the
GFA does not do this perfectly because the home reg happens before the local
reg..the opposite is true with Nested/Concat for that reason.

The other important piece of decoupling is the disparate address space
issue. I want to connect to multiple domains with HAs but do not want that
connection to force my local addressing decisions (hence 3G swiching and
tunnelling architecture). GFA does much better now with this issue but still
cannot support HoAs from multiple private HA domains because the FA loses
the source HA address which would have made it locally unique. Again Nested
supports this.

I think if you clearly limit your applicability to where the delay or
relative cost of signalling v MN data is excessive, and include the
decoupling arguments above then I hope people will be satisfied. This is
because they would argue and I would agree that 'normally' RegTun is
optional but not generally useful, as opposed to being optional and
generally useful as I think you would claim. The reason that want this clear
distinction is that they do not want to give the impression that MIP is
generally 'broken', which I agree with, whilst in addition I would argue it
is specifically and definitely broken in the cellular case with IP to the
basestation. Note that this is where deployment experience does not yet
exist but we are working on that :-)

Hopefully, that helps us all go forward ?

Regards,  Alan.

-----Original Message-----
From: Annika Jonsson [mailto:[email-masked]]
Sent: 14 May 2002 18:11
To: Madhavi W. Chandra
Cc: Phil Roberts; [email-masked]'
Subject: Re: [mobile-ip] Regional Registration Last Call Resolution
Issue #1

Hi Madhavi,

At 12:37 PM 5/13/2002 -0400, Madhavi W. Chandra wrote:
>HI Annika,
>
>On Mon, May 13, 2002 at 06:16:05PM +0200, Annika Jonsson wrote:
> > Hi Madhavi,
> >
> > see below...
> >

...

> > > > Attached below is modified text for the abstract and the
introduction,
> > > > Annika's words based on input
> > > > from Madhavi.
> > >
> > >DISAGREE...as written below.
> > >
> > >As per the feedback we provided, it should be clearly stated in the
> > >Abstract and Introduction that this architecture is OPTIONAL and not
> > >required in typical Mobile IP deployments.
> >
> > In the proposed text, both the Abstract and the Introduction _does_ say
> > that this is an optional extension to MIP, so what are you disagreeing 
> with?
>
>As I stated in the email above and in my writeup, it should say
>clearly in the Abstract and Introduction that the architecture is
>OPTIONAL *and not required in typical Mobile IP deployments.*  Since
>this is not what you wrote above, we are DISAGREEING.

To me, optional means just that, that it is not required, and that, I 
think, is clearly stated. I don't like the expression "in typical Mobile IP 
deployments". What is a "typical" Mobile IP deployment, and will it always 
be the same?

>
> >
> > >Also, reference to the new
> > >Section that will describe scenarios that may benefit from this
> > >architecture should be included in the Introduction. The agreement to
> > >include the new Section is to alleviate the doubts for the necessity
> > >of this architecture.  Hopefully, the new Section will highlight when
> > >the architecture is useful, and not when it is NOT.
> >
> > I think that the text in the Introduction gives sufficent information 
> about
> > what makes regional registrations useful and see no need for an extra 
> section.
>
>This is not what Charlie and I agreed to.  We agreed to a new
>Section that describes where this architecture would be
>useful...perhaps you can provide network architectures that would
>benefit from the regional tunneling.  As per the agreement, the new
>section would go into Section 3...probably Section 3.1 as Charlie
>mentioned.  Refer to the original email thread on this.  If we had
>thought that the Introduction was sufficient, the original email
>thread would not have occured.  Please do not go back to square one.

Sorry, I missed that. I went back to see what you and Charlie had written. 
You offered to help with  text, could you please do that?  I'm not really 
sure what you want in this new section, that's why I'm asking. In the 
Introduction now it says:

" If the distance between the visited network and the home network of the 
mobile node is large, the signaling delay for these registrations may be 
long. We propose a solution for performing registrations locally in the 
visited domain: regional registrations."
<snip>
Regional registrations reduce the number of signaling messages to the home 
network, and reduce the signaling delay when a mobile node moves from one 
foreign agent to another, within the same visited domain. This will both 
decrease the load on the home network, and speed up the process of handover 
within the visited domain. "

What would you like to add to that?

Regards,
Annika

>Thanks,
>Madhavi
>
>
> > Regards,
> > Annika
> >
> > >I have provided Annika with the suggested text.  Please incorporate
> > >the above comments.
> > >
> > >Thanks,
> > >Madhavi
> > >
> > >
> > > > Phil
> > > >
> > > > "Abstract
> > > >
> > > > Using Mobile IP, a mobile node registers with its home agent each 
> time it
> > > > changes care-of address. If the distance between the visited 
> network and
> > > > the home network of the mobile node is large, the signaling delay
for
> > > these
> > > > registrations may be long. This document describes a new kind of
> > > "regional"
> > > > registration, i.e., registration local to the visited domain. The 
> regional
> > > > signaling is performed via a new network entity called a Gateway 
> Foreign
> > > > Agent and introduces a layer of hierarchy in the foreign domain. 
> Regional
> > > > registrations reduce the number of signaling messages to the home 
> network,
> > > > and reduce the signaling delay when a mobile node moves from one 
> foreign
> > > > agent to another, within the same visited domain. This document is
an
> > > > optional extension to the Mobile IP protocol."
> > > >
> > > >
> > > > "Introduction
> > > >
> > > > This document is an optional extension to the Mobile IP protocol,
and
> > > > proposes a means for mobile nodes to register locally within a
visited
> > > > domain. By registering locally, the number of signaling messages to
the
> > > > home network are keept to a minimum, and the signaling delay is 
> reduced.
> > > >
> > > > In Mobile IP, as specified in RFC 3220 [9], a mobile node registers 
> with
> > > > its home agent each time it changes care-of address. If the distance
> > > > between the visited network and the home network of the mobile node
is
> > > > large, the signaling delay for these registrations may be long. We 
> propose
> > > > a solution for performing registrations locally in the visited
domain:
> > > > regional registrations. The regional registration design introduces
new
> > > > Mobile IP messages - Regional Registrations, new Mobile IP 
> extensions to
> > > > convey information between the mobile node, foreign agent, and home 
> agent,
> > > > and a new network entity - Gateway Foreign Agent (GFA). Regional
> > > > registrations reduce the number of signaling messages to the home 
> network,
> > > > and reduce the signaling delay when a mobile node moves from one 
> foreign
> > > > agent to another, within the same visited domain. This will both 
> decrease
> > > > the load on the home network, and speed up the process of handover 
> within
> > > > the visited domain. The introduction of a GFA also makes it possible
to
> > > > have different addressing realms in the home and in the visited 
> networks."
> > > >
> > > >
> > > > The last three paragraphs of the Introduction are unmodified.

---

From: "Madhavi W. Chandra" <[email-masked]>
Date: Thu, 16 May 2002 10:07:55 -0400

Hi Alan,

Nice clarification!  You have correctly captured
our concerns.  I hope your suggestions will be incorporated
into the draft.  If so, I'm sure the contentious issues with
the draft will abate...else, I'm afraid the circle will continue.  

Regards,
Madhavi