Subject: Re: [nemo] comments on "Tree Discovery" draft

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 26 Aug 2004 11:00:25 +0200

Pascal Thubert (pthubert) wrote:
>> existing graph.  And, speaking of which, I'm sure OSPF builds 
>> spanning trees, which may even be minimal.
>> 
>> Which leads me to offer my humble point of view replying to your 
>> request: investigate instead the use of OSPF within an aggregation
>>  of moving networks.  Which raises the question: why not.
>> 
> Well the key is how quickly things come up, and how the solution 
> being deployed survives quick movements. TD is optimized to obtain 
> one tree, and it does it in one pass.

Look, I'm eager to find a more expressive definition of this "quick"
word.  What is a "quick movement" by the way.  In Mobile IP terms, it is
something related to how often the CoA is changed per time unit (e.g. 3
CoA changes per second is quick, 1 CoA per second is normal and 10 CoA
per second is very quick).  Note how different is this from the physics
terms where speed is physical distance over time; this physical
"quickness" is in no way related to the Mobile IP quickness because
there may be very large rectilinear areas where you go 220km/h and still
don't change the CoA (Mobile IP "quickness" is really below normal).

So, having this in mind, do you have an idea of a practical setup where
the NEMO MR's nest and form aggregations and at the same time they are
very "quick" in terms of Mobile IP to each other.

> If you are interested in the applicability of OSPF in a MANET 
> environment, please have a look at the activities that now take place
>  in the OSPF and MANET WGs on that respect. You'll find that it's a 
> great idea and that there's a lot of work to get there. One good 
> thing for MANET is that OSPFv3 uses linklocal whereas v2 requires 
> that peers have an address on the same network.
> 
> Then again, it would be slower than TD for many applications. TD is 
> not a routing protocol, it's much simpler and quicker. It does just 
> what nested nemo needs to get out.

TD is quicker than what?  TD is "quicker" like accomodating quicker MR
movements?  How many CoA changes per second per MR would TD support
compared to OSPF?

Alex

---

From: "Pascal Thubert \(pthubert\)" <[email-masked]>
Date: Thu, 26 Aug 2004 09:47:29 +0200

> > 2) TD is a proposed solution for issue 24. One question is whether
> > people feel that this is a real important issue for NEMO, whether
its
> >  RO only, whether we need to do anything here at all. I'd appreciate
> > your point of view on this.
> 
> I doubt the name Tree Discovery fits.  I'd call it Tree Building (like
> in team building) or something.  In a graph topology there's no tree
to
> be discovered but rather a sort of virtual tree to be overlayed over
the
> existing graph.  And, speaking of which, I'm sure OSPF builds spanning
> trees, which may even be minimal.
> 
> request: investigate instead the use of OSPF within an aggregation of
> moving networks.  Which raises the question: why not.
> 
Well the key is how quickly things come up, and how the solution being
deployed survives quick movements. TD is optimized to obtain one tree,
and it does it in one pass. 

If you are interested in the applicability of OSPF in a MANET
environment, please have a look at the activities that now take place in
the OSPF and MANET WGs on that respect. You'll find that it's a great
idea and that there's a lot of work to get there. One good thing for
MANET is that OSPFv3 uses linklocal whereas v2 requires that peers have
an address on the same network. 

Then again, it would be slower than TD for many applications. TD is not
a routing protocol, it's much simpler and quicker. It does just what
nested nemo needs to get out.

Pascal