Subject: [seamoby] IRTF mm problem statement

From: Phil Roberts <[email-masked]>
Date: Mon, 30 Apr 2001 14:56:23 -0400

Hi folks,

   a draft of an IRTF problem statement for host routing is now available
at:
http://www.diameter.org/draft-proberts-hostrouting-problem-00.txt.  I'd like
to run it by the working group before submitting it as an I-D.  All comments
and suggestions are welcome.  It would probably help if it had a set of
proposed deliverables.

Phil

---

From: "Phil Neumiller" <[email-masked]>
Date: Mon, 30 Apr 2001 15:32:19 -0500

Hi Phil R,

I had MANY questions and comments on the IRTF MM problem statement.
They are contained below.

In the Abstract

>There are a couple of seemingly unrelated problems that
> have lead investigators to converge on the desirability of new
>routing protocols to implement host routes within a constrained area.

The wording of the above sentence could be confusing for MIP/SeaMoby
"outsiders". I suggest SOMETHINK LIKE :

...routing protocols that allow for a mobile host to implement a limited
host routing table to other mobile hosts in the same constrained routing
area.

HOWEVER, This seems to beg the questions of:

A).  Why not use IPv6 MN to MN direct routing optimization?
B).   All MNs will be MANET capable in the future.  If so, they
        don't they already have a sophisticated host routing algorithm?

>The problem is to investigate the limits and issues with using (a)
>new protocol(s) to implement host routes to facilitate better mobile
>hosts and network recovery in the presence of failed links or
>routers.

To be fair, you MUST add that there are perceived deficiencies
in using MIP all the time.  These must be quantified and qualified
by the IRTF.  Specifically, how fast is a fast handoff, and WHEN
IS USING HOST ROUTES EVEN DESIRABLE?

>The document is a brief statement of the problem to be
>investigated with lots of references to other work that has been done
>already by many others in the area.

I would reword "with lots of references .. "  with "and the references
to lots of prior work in this area have been included in this draft."

>1. Introduction
>   The design of Internet routing has evolved largely based on the
>   assumption  that most end systems are static.

Not really true.  The foundational pieces of the Arpanet and early
Internet were all wireless and the MANET work is completely
wireless mobile based routing.

>   As the idea of mobile
>   devices came along,  Mobile IP provided an easy migration path for
>   supporting end system mobility without significant change or impact
>   to the Internet infrastructure. This was achieved primarily by
>   placing the support for routing to mobile devices on the end systems
>   and at a limited number of centralized points within the
>   infrastructure, effectively "hiding" the end system mobility from the
>   infrastructure routing protocols. However, as we anticipate the
>   desire to support real-time traffic flows to mobile devices and the
>   possibility that mobile devices may become a significant portion of
>   all Internet end nodes, investigation of alternative designs merit
>   consideration.

Are we really talking about an alternative design?  I don't think so.
In this case we are talking about an extension.  Now if we were talking
about replacing MIP with something like BGP (which could happen
in the not too distant future) we would be talking about an "alternative"
design to MIP.

>   Many investigators in this area have converged on
>   solutions that propose the use of host routing to support mobility
>   within a limited domain, effectively exposing the mobility of end
>   systems to the routing protocols.

Yes, an MANET has been working on this for years.  I don't think
that's what we want to say here Phil.  What we need to do is talk
about is localized host routing and WHAT it means to be local,
i.e. how many hops, what kind of hops, how is MIP involved and
how does it inter-work.

>   This draft represents a problem statement to enable investigation of
>   the use of host routing in IP networks to enable mobility and fast
>   network recovery.

... AND to take over for MIP when MIP is not the correct solution.

>   It is a problem statement based on a lot of work
>   done in attempting to provide low latency handover in mobile networks
>   and fast recovery in networks with fast recovery requirements.

If fast recovery is important, MANET has the fastest non-looping and
looping (Distance vector and link state routing) algorithms and protocols
around.  Fast recovery of what Phil?  The link?  The MN to AR path?
The MN to MN path that bypasses MIP???

<<SNIP>>

>2.1 Part One
>
>   Why is there a perceived need for host routing?  There are
>   applications that involve supporting real-time traffic flows to end
>   devices that are mobile.  These applications require that there be
>   minimal (ideally no) interruption to the packet flows and that these
>   flows need to preserve the existing QoS and security characteristics
>   as the end station moves.  In addition the movement of the end
>   devices should not cause excessive signaling in the network as the
>   devices move.

>   Such applications often also run on networks in which
>   link failures or router failures can cause a significant service
>   disruption.  Is it possible to use a similar protocol to allow for
>   faster restoration of service during link failures.  Could such
>   mobility requirements and fast restoration requirements be met in a
>   way that is more efficient and simpler than approaches based on
>   Mobile IP and OSPF by using a routing protocol that implements host
>   routes within a limited scope within the network?

Questions:
A).  I DONT think link failure is the issue here at all!  Its the limitations of MIP.
       the heart of the issue is for the IRTF to find what the MIP limitations are
       so that WE KNOW WHEN WE MUST (or it is desirable to) use HOST
       ROUTES!!!

B).  Why mention OSPF?  Last time I checked, most of the Internet was
       built with distance vector routers (from Cisco :-)).

C).

>  What would the
>   limits of such a solution be in terms of scaling?

What are the limitations of MIP that force us to consider this solution?

>   Specifically how
>   many nodes could be supported across what kind of network breadth and
>   depth at what cost of complexity in the routers around the edge of
>   such a network?

Completely insane routing tables based on brownian motion mobiles have
been simulated up into the 10K+ numbers with both distance vector (Bellman
Ford) and link state (Dykstra) approaches for MANETs.  Again this seems to be
asking the question in reverse!  What we want to be asking is how SMALL
can MIP get before IT wear's out its welcom, i.e. other solutions are more
optimal.  These are the numbers we need.

>   Is it possible to meet traffic engineering
>   requirements using such a protocol?

It is possible to meet traffice engineering requirements with MIP?  Where
does MIP break so we know if these things are EVEN NEEDED!!!

>  Could it simplify management of
>   QoS in the part of the network where mobility is most readily felt?

Localizing protocols to where the dynamics are occuring JUST MAKES
so much sense.  Hiding movement from upstream MIP entities or CNs
makes lots of sense.  What we need to understand is under which conditions
is this NECESSARY.  How often can a CN be informed of a BU?  Nobody
knows.

>2.2 Problem Two
>
>   One of the primary principles of the Internet has been end-to-end
>   communication. Most (if not all) of the protocols running over IP
>   have been designed with end-to-end signaling in mind.  Currently,
>   changes due mobility induce unwanted end-to-end signaling. This may
>   cause applications running over IP to fail due to delay and latency
>   induced by unwanted signaling.  Security, QoS and AAA signaling all
>   suffer due to this.  Could a host based routing aid in this respect?

A).  "due mobility" -> "due to mobility"
B).  This seems to be presented in reverse terms to me.  Host routing
is returning to end-to-end signalling as opposed to box-in-the-middle
signalling used by MIP.  The CNs that are local to an area and that
can speak with each other end-to-end are presumably doing this
faster than having to relay and signal through a home agent!!!

>2.2 Problem Three
>
>   Why is there a need for an investigation of it in the IRTF rather
>   than a direct move to work on a standard within a working group of
>   the IETF?  The area directors overseeing the activities of the
>   seamoby working group and the mobile-ip working group have raised
>   questions about the scale of host routing and the need to introduce
>   both another routing protocol and another mobility protocol. A
>   comparison with OSPF and Mobile IP are involved in making such an
>   assessment both in terms of relative scalability, performance, and
>   complexity.

A). Why OSPF?
B). Why not BGP?
C). The primary issue needed is to expose the limitations of MIP and
harden what we know about MIP quantitatively so ANY holes can
be filled with local mobility management protocols.  I can not emphasize
this enough.  THIS IS THE primary REASON.  The secondary REASON
is to investigate if host routes deployed in a limited scoped way (where the
limitations are set by what MIP can't do) is reasonable.  Also, carefull
analysis of where the MANET boundary is also required.

Thanks,

Phil Neumiller