Subject: [nemo] comments on draft-ng-nemo-multihoming-issues-00

From: William D Ivancic <[email-masked]>
Date: Mon, 17 Mar 2003 14:30:11 -0500

Many thanks to the authors of draft-ng-nemo-multihoming-issues-00 for 
taking time to describe in detail many of the various ways the multihoming 
may occur.

I have a few comments regarding the described scenarios.

==============================================================================
Regarding 2.1.1 Single Mobile Router with Multiple Egress Interfaces Bound 
to a
                 Single Home Agent

IMHO this scenario MUST be addressed.  I believe this will be one of the 
more common scenarios. As both egress interfaces may be active 
simultaneously, I suggest the at least one interface MUST be utilized and 
could be selected by some prioritization.  In addition, all interfaces MAY 
be utilized  for load sharing, priority routing and numerous other reasons 
I cannot currently identify.   I suggest, however that it would be well 
advised to allow for the first mode of operation for the following 
reason:  Lets assume I have a satellite link on egress interface 1 at 64 
kbps at a cost of $1 per minute and $10,000 per antenna/communication 
system (a bargain price) and a second 802.11b link at 11 Mbps on egress 
interface 2 at a cost of $80 per month and under $1,000 for the mobiles 
antenna system.  I would surely like to not use the satellite when I have 
802.11 connectivity.

=============================================================================
Regarding 2.2.2 Single Mobile Router with Multiple Egress Interfaces Bound to
                 Different Home Agents

I think there are some definite security issues that must be addressed here 
as we are tying two administratively different networks together.

Also, I am assuming or suggesting for this scenario the each HA is 
advertising a different network.  That is the same mobile network is not 
advertised by two independent HAs in two geographically different locations 
by two independent ISPs.  Otherwise, some type of communication would have 
to occur between the HAs in order to avoid routing loops.

================================================================================ 

Regarding 2.1.3.  Multiple Mobile Routers

Relative to the mobile network node, assuming it is attached to two MRs, it 
can either pick one as the default router, or perform load sharing or 
utilize both links in other ways.  Here, the mobile network node is 
multihomed.  I don't think this is much of an issue accept relative to 
security issues as again, we may be tying two independent networks together.

It may be technically possible to allow one of the Mobile Routers (here 
MR-1) to utilize the others (MR-2) connectivity when MR-1 looses 
connectivity to its Access Router via its egress interface.  I am not so 
sure that this would administratively be allowed.  However, I think this 
could be a MAY, but not a MUST.

Will

---

From: Greg Daley <[email-masked]>
Date: Tue, 18 Mar 2003 13:11:00 +1100

Hi Will,

Just a quick comment on one of the scenarios.

William D Ivancic wrote:
[scenario snipped]

> ======================
> I think there are some definite security issues that must be addressed 
> here as we are tying two administratively different networks together.
> 
> advertised by two independent HAs in two geographically different 
> locations by two independent ISPs.  Otherwise, some type of 
> communication would have to occur between the HAs in order to avoid 
> routing loops.  
[scenario snipped]

I think that the idea with NEMO was that no transit
is provided between ASs by the NEMO (except for
nested NEMOs lower in the DAG).
This is especially important in IPv6 where this is not
generally allowed anyway.

Greg

---

From: Chan-Wah Ng <[email-masked]>
Date: 19 Mar 2003 02:55:31 +0800

> generally allowed anyway.

What happen if the MR, say use two level of tunnelings, to forward
packet to HA-1, via HA-2?  Would you still consider this as disallowed?

It will be something like this:

MN send packet A, src=home-link-1
MR encapsulate packet A in packet B, dst=HA-1
MR encapsulate packet B in packet C, dst=HA-2

/cwng

---

From: William D Ivancic <[email-masked]>
Date: Tue, 18 Mar 2003 20:37:07 -0500

>MR encapsulate packet B in packet C, dst=HA-2

Hello Chan-Wah,

Let me take the liberty to add some numbering for clarity - I hope the 
intent of your question is unchanged.

In referencing the diagrams of 2.2.2 of the multihoming draft, 
draft-ng-nemo-multihoming-issues-00
Single Mobile Router with Multiple Egress Interfaces  Bound to Different 
Home Agents

MN (attached to MR1 only) send packet A, src=home-link-1
MR1 encapsulate packet A in packet B, dst=HA-1
MR2 encapsulate packet B in packet C, dst=HA-2
HA-2 de-encapsulates packet C and forward B to HA-1
HA-1 de-encapsulates packet B and forwards to the corresponding node.

I assume from this description presented as  that the MN is attached to 
only MR1 and that MR1 looses its connection to its Access Router.  Then if 
appropriate security mechanisms occur such that MR2 allows MR1 access to 
its network, than this should be permitted.
If MN was attached to both MR1 and MR2, there would be no reason to use MR1 
if MR1 looses connectivity to its Access Router(s).

Will

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From: Chan-Wah Ng <[email-masked]>
Date: 19 Mar 2003 10:11:02 +0800

> >MR encapsulate packet B in packet C, dst=HA-2
Hi, William,

> intent of your question is unchanged.

Great, thanks for improving it :).

> if MR1 looses connectivity to its Access Router(s).
Agreed, in the steady-state MN should not.  But see if me reasoning make
sense:  it takes time for MN to discover that MR-1 is no longer up, and
to switch over to use MR-2 (plus getting Coa and sending BU).  So for
real time applications, MN may wish to continue using MR1 until the new
binding update is set up.

Make sense?

/cwng

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From: William D Ivancic <[email-masked]>
Date: Tue, 18 Mar 2003 20:37:07 -0500

Hello Chan-Wah,

Will