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

From: "Pascal Thubert \(pthubert\)" <[email-masked]>
Date: Thu, 26 Aug 2004 15:58:22 +0200

> > Sure. Is issue 24 a problem that we want to handle for NEMO?  Or do
> > we leave it all to MANET/OSPF?
> 
> As I said in my reply on Issue 24 itself, I do not see that to be a
> problem.  The looping described in issue 24 assumes simultaneous L2
> connectivity of one interface to two wireless access systems,
something
> impossible.  That problem has not been refined since.  That is not a
> problem, and so it can not be solved in NEMO and in no other WG
present
> or future.
> 
> The RA confliction problem can never appear in practice once the
various
> wireless access systems covering a common area are (1) different in
> nature, frequency, encoding or (2) protected by different sec keys.
If
> two such systems fail both conditions, L2 connectivity is unclear, a
> much bigger problem that the little NEMO Mobile IPv6 support.

The so called RA confliction is just a very narrow instance of the loop
problem. Jari's case had 3 routers forming careofs from each other in a
loop. No way out. The discussion was that since they can not bind, one
would eventually try a careof from an available AR and make it. Then
another would eventually use that successful MR and bind via it, etc...

Obviously, this takes the longest time and does not produce an optimal
path to the outside.

Pascal

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 26 Aug 2004 16:30:42 +0200

Pascal Thubert (pthubert) wrote:
> The so called RA confliction is just a very narrow instance of the 
> loop problem.

I'd say the reverse.  The RA confliction problem is more generic and the
Jari problem is very narrow; RA confliction description involves only
one router and with it says all, no need to depict three routers to
express the same problem.

RA confliction problem has a MR with two wireless interfaces.  The
egress interface receives RA from the ingress, configures CoA and sends
BU over wireless towards its own ingress interface, receives it, and
will not encapsulate it again towards its egress interface because it
has not yet received a BAck.  Actually this BAck will never come so no
loop nor infinite encapsulation.

The RA confliction problem assumes that the egress and ingress interface
of MR can talk to each other wirelessly.  In 802.11b this is the case
_only_ if they both use ESSID, or same keys, or same ad-hoc mode, or any
other same something.  This is bad configuration, not bad protocol.

Please disagree with a more exact setup using any wireless techno.

> Jari's case had 3 routers forming careofs from each other in a loop.
>  No way out. The discussion was that since they can not bind, one 
> would eventually try a careof from an available AR and make it.

YEs, and at this exact point, when this successful MR connects to AR it
cuts its egress connection to any other MR (keeping its ingress).  Thus,
no loop.

> Then another would eventually use that successful MR and bind via it,
>  etc...

Fact which does not lead to a loop.

Alex