Subject: RE: [nemo] Multiple Egress vs multihoming

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Thu, 22 May 2003 09:35:03 +0100

Hi Chan-Wah. 

I think we're not in sync yet. I did not ask you to describe configs,
but what problems need to be solved. I gave my view as example of what I
asked from you for the 4 problems that I see. If you see other problems
to be solved please detail them that way. Otherwise we're in a loop, and
I'll quit. This is my last attempt to make you understand what I mean.
Otherwise I guess it'll show up later. 

> Okay, here are the 8 in (w,x,y) tuple: (these are written just off my
> mind, so pardon me if they appear to lack careful analysis)
> 
> (0,0,0) = One MR, one HA, one prefix
> As far as I see it can either have more than one care-of-address
> addressed to one HoA (multiple interface sharing same HoA but
different
> CoA), or it can have different CoA-HoA pairs.  Either way, it should
be
> a MIPv6 problem.

Right. It must be clear that this case is about multiple CareOfs
registered in parallel as opposed to multiple interfaces active in
parallel. This case is the Tarzan problem of load balancing, fast
handoff and so on as I described earlier.

> (0,0,1) = One MR, one HA, multiple prefix.
> If the MR has only one HoA with multiple CoA and multiple subnet
prefix,
> we need a way for HA to be able to register that the multiple prefixes
> are tied to that HoA.  I guess it should be a NEMO problem.
> 

What is the new problem? This is several times the (0,0,0) problem. The
only thing to discuss is if we use a single or multiple binding message.
But there's no design problem.

> (0,1,0) = One MR, multiple HA, one prefix
> Can MR register the same HoA in two different HAs?  If not, the
problem
> is simply a HoA-CoA pair per HA.  There is also the question of same
> prefix-careof in two different HA.  Need to analyse further.
> 

We are multihoming the prefix. Who cares if the MR uses a single or
multiple home addresses or CareOfs. The key is to allow registering the
same mobile prefix to several HAs. The problem I see is the JetSet
problem as I detailed before, which has to do with optimized routing.
Also, if the HAs are hops away, we'll need to have the L3 HA-HA
coordination protocol by then, but that much is not a multihoming issue
per se, it has more to do with whether we want a physical home net or
not).

> (0,1,1) = one MR, multiple HA, multiple prefix
> largely similar to (0,1,0), but now you have additional prefix coming
> in.  This may be easily solved if we demand that each prefix be taken
> care of by separate HA.
> 

What is the new problem? This is several times the (0,1,0) problem. The
only thing to discuss is if we use a single or multiple binding
messages. But there's no design problem. Did I write this before?

> (1,0,0) = multiple MR, one HA, one prefix.
> May not have any problem at all if the MRs are manually configured to
> announce same prefix.  Prefix delegation is also possible since the
MRs
> are handled by same HA.  HA will see two HoA-CoA pair sharing taking
> care of the same subnet prefix.
> 

This is the Shinkansen problem I explained before. Mostly deals with
balancing the flows between the 2 MRHA tunnels when both are active, and
with redirecting all the traffic to the active one if only one is
active. I agree that on top of that, the prefix delegation should know
that the 2 MRs are paired and affect the same prefix to both, but this
seems to be a config issue only. Note that the 2 MRs do not have to be
both registered at a given point of time (one may be hot stand by).

> (1,0,1) = multiple MR, one HA, multiple prefix
> May not have any problem at all if each MR take care of separate
prefix.

This is the double Bed problem if the different MRs have different
prefix. I tried to show that this relates to the MR not being a stub. So
I suggested to rule that out quickly.

> (1,1,0) = multiple MR, multiple HA, one prefix
> Question of multiple HA handling the same prefix.
> Also question of how to do prefix delegation between two MRs with
> different HA.
> 

What is the new problem? You just say it yourself, this is the (1,0,1)
problem coupled with the (0,1,0) problem. 

> (1,1,1) = multiple MR, multiple HA, multiple prefix
> May not have any problem at all if each MR take care of separate
prefix.

What is the new problem? This is the (1,0,1) problem coupled with the
(0,1,0) problem.

Pascal

---

From: Chan-Wah Ng <[email-masked]>
Date: 22 May 2003 17:42:19 +0800

Hi Pascal, Julien,

> Otherwise I guess it'll show up later. 

I fully understand what you want, but you seem not to understand my
standpoint.

You want to see the specific problems of multhomed NEMO.  You came up
with 4.

Instead of coming to the quick conclusion as you have, we decided to
start by classifying NEMO into different configurations.  From these
configurations, we then identify the problems.  As I have already stated
in previous mails, it may well be among the 8 configurations, we
identify the same 4 problems as you did.  But only through the exercise
of looking into each configuration can we be sure that these are the
only 4 and no more.

I am now in the process of identifying individual problems in each
configuration, and will release the I-Draft once that is done.  So
please be patient for this couple of days.  In that aspect, your
comments on the 8 configurations are useful, and I thank you for that. 

/cwng