Subject: Re: [MOBILE-IP] Some novice questions!!!

From: Patrice Calhoun <[email-masked]>
Date: Fri, 4 Aug 2000 10:27:25 -0600

>Hi Gurus,
>
>Sorry for asking these stupid questions:
>
>1) What is soft handoff, hard handoff and fast handoff?

Here's my take.

soft vs. hard hand-off are terms that actually have very specific meanings
in CDMA. I believe that the IETF should use fast handoff, which carries no
baggage.

Of course, this week we've heard of express handoff, so I am proposing
changing my Internet Draft to hyper-speed handoff :) :)

>
>2) Is the mobile-ip already implemented in present-day consumer networks or
>it is still a proposition?

implemented, and available in Solaris 8 update 1.

>
>3) Cellular-ip, HMIP and UMIP: Which one is better and why?

I believe that I will not touch this one with a 10 foot pole.

PatC

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From: Karann Chew <[email-masked]>
Date: Fri, 4 Aug 2000 16:12:53 +0100

Dear All,

I noticed that proposals such as Cellular IP, HAWAII etc. (which seem to
be able to solve fast handoff or micro-mobility or intro-domain
mobility problem) are not favoured by a lot of people in MIP WG.  Well, at
least not as popular as drafts such as Route Optimzation, Regional
Registration etc.  Could someone please explain why.

What I can think of are that RO, RR is more conform to RFC2002; have a
more well-defined security procedures...

Thanks in advance.  Cheers!
        Karann

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From: Arthur Ross <[email-masked]>
Date: Fri, 4 Aug 2000 08:37:48 -0700

>in CDMA. I believe that the IETF should use fast handoff, which carries no
Short description: "Soft" handoff in CDMA entails a make-before-break state
during which diversity combining of signals from multiple stations is used
to improve error performance. "Hard" handoff doesn't do that. Soft handoff
is, in some loose sense, a state; hard handoff is a state transition.

"Fast" seems to me to be a different coordinate axis of the problem :-)

   -- A

   Dr. Arthur H. M. Ross
   2325 East Orangewood Avenue
   Phoenix, AZ 85020-4730

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From: Ramachandran Ramjee <[email-masked]>
Date: Fri, 4 Aug 2000 17:59:33 +0000

Hello,

Here  is my take on fast handoffs. There has been a spate of
drafts recently on handoff support and the working group is
trying to unify them to one proposal.  While the net
outcome of this might indeed be one draft, that ONE DRAFT WILL
END UP LISTING MULTIPLE HANDOFF SOLUTIONS FOR DIFFERENT LINK
LAYER/WIRELESS NETWORK SCENARIOS (this is one of the reasons
why we keep hearing objections from some quarters saying fast
handoff should be left to the link layer folks themselves and
not the mobileip wg!).

I think what we need is a FRAMEWORK FOR HANDLING MOBILITY LOCALLY.
Inside this framework, there must be freedom to tailor handoffs
in any way, based on link layer or other characteristics. This
framework will also allow registrations to be processed locally,
reducing signaling load to the home agent. Also,
such a framework will help support paging within the network agents
(which is another local function) and ipv6 (which will initially be
a local function as the transition from ipv4 takes place).

Currently, there are two such broad frameworks available:

1) HAWAII/CIP - every local node is involved, no tunneling
2) HMIP/UMIP/RR - a few local nodes are involved, tunneling-based
overlay

I think both frameworks are/can be made to look like rfc2002
with similar security models.

So, the real issue is do we want an overlay or not in the local wireless
access network? Once the wg decides on this, we can then decide on ONE
FRAMEWORK document that specifies how mobility is handled locally
(for example, if the decision is to use the overlay network approach,
we can then decide on merging the HMIP/UMIP/RR proposals).
THEN, fast handoffs and everything else will have a structure to
work with and we no longer need just one fast handoff standard.

Comments please?

Cheers,
Ram

P.S. Answering your question on the popularity of different
micro-mobilty proposals, the ability to do all local functions
such as  paging/fast handoffs/regional registrations etc. in one
framework in HAWAII/CIP is, I think, causing more resistance in the wg,
while in the Hierarchial approach, there is multiple drafts each
addressing one piece of the puzzle, making it easier to digest.

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From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 7 Aug 2000 09:50:06 -0700

Hello Ram,

I agree with what Basavaraj has said, but it's also possible that the
_general_ layer-3 handover documents could have specific sections
that were relevant for a subset of link layers.  In any case, there
should be clear statements of applicability.

I do not think that Cellular-IP and HAWAII represent general
frameworks for fast handover.  I think they represent integrated
solutions with features for supporting  localized registration and
fast/smooth handovers.

For the former, I would really like it (being biased and all) if you
would be able to make comments about how the current Regional
Registration draft might or might not be useful for supporting the
needs for HAWAII.

Regards,
Charlie P.

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From: Ramachandran Ramjee <[email-masked]>
Date: Mon, 7 Aug 2000 17:55:42 +0000

Hello Charlie,

I am not sure what your definition of handoff framework is.
I meant a framework as a structure around which different handoff
schemes can work - for example, in HAWAII, the structure is
the access network itself, with the ability to support multiple
handoff schemes (termed path setup schemes in the draft).

Similarly, I think Hierarchical FA has a structure made up of
FA's -  my main issue with this is that a dynamic configuration/
failover protocol for the various FAs is necessary in order to
not introduce new single-points-of-failure elements.

Regarding your question about RR and HAWAII,
I think the ability to separate authentication between
local and home (with the admissible authentication term you
added in the rfc2002-bis) is needed for all drafts that allow
regional registration. Regarding messages/extensions defined
in the RR draft - the GFA extension and the HFA extension are specific
to RR...we could potentially make HAWAII messages
also look similar with Old BS, New BS extension etc.

Cheers,
Ram

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From: Wolfgang Schoenfeld <[email-masked]>
Date: Tue, 8 Aug 2000 17:29:01 +0200

Dear Colleagues,

for the ongoing -very interesting- discussion on fast handoff,
the following notion might be useful
which we developed to better understand
(and teach) the proposed solutions.

We started from usual mobile networks,
i.e. networks with frequently changing topology
where routing has to be adapted appropriately.
Most mobile networks like GSM have a tree-like structure,
and their diameter (=maximal distance) is about 10.
(Updating routing tables is hard for non-tree topologies.)

Now, a virtual mobile network (VMN) is a mobile network residing,
as a new layer, above a stationary network (e.g. IP).
A link in the VMN is just a path (or set of thereof)
in the underlying stationary network (tunnel).
What singles out a VMN (from e.g. virtual private networks)
is that its points of attachment
to the underlying stationary network ("binding") may change.
(Maybe, this is what "overlay" expresses in Ramachandran's Email.)

Mobile IP is a VMN of diameter 3 (if we count CN--HA as 1 hop).
It is not a tree (instead, it is a "clique" with 1-hop appendices).
HMIP is a tree with unbounded (?) diameter,
RR is one with diameter slightly larger than 3.
CIP is ...

This concept of a VMN helps to separate concerns,
e.g. binding from routing table updates,
and fits into the standard method of structuring by layers.
Please note that I chose "diameter" just as an example
of a discriminating parameter.
Others are life-time of binding/routing entries etc.

Wolfgang
-----------------------------------------------
Wolfgang Schoenfeld, GMD-IPSI, +49-6151-869-865