Subject: [netlmm] Ticket #166: Host Multi-Homing

From: Christian Vogt <[email-masked]>
Date: Tue, 31 Jul 2007 10:54:53 +0300

Folks,

I added this issue to the tracker.

Best regards,
- Christian

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Ticket #166 (new technical):  Host Multi-Homing

Host multi-homing seems to be in architectural conflict with P-MIPv6. A
multi-homed host has two interfaces that attach to different links.
There are 3 questions related to this:

- How can it be ensured that the mobile node configures the same HoA on
each of its interfaces?

- How can all of the MAGs that the mobile node attaches to
simultaneously have a binding with the mobile node's LMA?

- To which interface of the mobile node should the LMA forward packets
received for the mobile node?

This issue was brought up by Hesham Soliman during the NETLMM session at
IETF 69 in Chicago. See also:
http://www1.ietf.org/mail-archive/web/netlmm/current/msg02665.html

There is consensus in the WG that host multi-homing should not be
supported by the current P-MIPv6 specification. Whether or not host
multi-homing should be explicitly forbidden in the specification is
still an open question.

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From: "Narayanan, Vidya" <[email-masked]>
Date: Tue, 31 Jul 2007 16:19:51 -0700

<WG Chair Hat Off>

Hi Christian, all,
Some comments inline.  

> Host multi-homing seems to be in architectural conflict with 
> P-MIPv6. A multi-homed host has two interfaces that attach to 
> different links.
> - How can it be ensured that the mobile node configures the 
> same HoA on each of its interfaces?
> 

It is not just about how the MN configures the same address on each of
its interface, is it?  The multiple interfaces that the MN has may be
going to different MAGs associated with different LMAs, for instance.
Also, it is a question of whether the MN wants to have those interfaces
as multihomed at the IP level.  

> simultaneously have a binding with the mobile node's LMA?

Given that the base spec is not dealing with multiple bindings, support
for this doesn't seem inline with the scope of the base spec. 

> - To which interface of the mobile node should the LMA 
> forward packets received for the mobile node?
> 

This seems tied to whether the LMA has multiple bindings for the MN or
not.  This doesn't seem applicable, given that there are no multiple
bindings with the basic PMIPv6 protocol. 

> This issue was brought up by Hesham Soliman during the NETLMM 
> session at IETF 69 in Chicago. See also:

I think Hesham had also raised the issue about having the same prefix as
the MIP6 home prefix and a PMIP prefix for the MN on another interface.
While in general, multihoming raises some issues with PMIP6, the
situation seems to get even further complicated with the same
address/prefix is being handled by MIP6 and PMIP6. 

> There is consensus in the WG that host multi-homing should 
> not be supported by the current P-MIPv6 specification. 
> Whether or not host multi-homing should be explicitly 
> forbidden in the specification is still an open question.

I'm not sure what it means to forbid something in an IETF document :) We
need to clearly state what is in scope and what is out of scope for the
document, but, we cannot prevent a deployment from actually doing
something.  However, I think both the base document and the interactions
document should explicitly state that the documents do not support
multihoming and that the protocol is only scoped to cover a single IP
interface on the MN.  

</WG Chair Hat Off>

Thanks,
Vidya