Subject: [Monami6] Host with multiple addresses of the same prefix

From: Gábor Fekete <[email-masked]>
Date: Thu, 4 May 2006 19:55:42 +0300

Hi,

Is a host considered multihomed if it has two different IP addresses
but both of those addresses have the same prefix?
That is, two IP addresses from the same IP subnet.

If not, why not? Maybe 
draft-ietf-monami6-multihoming-motivation-scenario-00.txt Section 2 should at 
least say that this scenario just makes no sense or won't really happen.

Also, draft-wakikawa-mobileip-multiplecoa-05.txt in Section 3.1 says that
the MN MUST register all its CoAs with the HA if it wants to register multiple
bindings.
So, I wonder if the above case (multi coa, same prefix) can
ever happen and if yes then how draft-wakikawa-mobileip-multiplecoa-05.txt
handles it.

Regards,
Gabor

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From: MARCELO BAGNULO BRAUN <[email-masked]>
Date: Thu, 04 May 2006 20:54:29 +0200

Hi,

this is common in the fixed case for instance for a server than wants 
to achieve fault tolerance and has multiple interfaces all connected to 
the local LAN.

now, i am not sure if such case makes much sense in the mobile scenario...

regards, marcelo

-- 
----
MARCELO BAGNULO BRAUN
WebCartero
Universidad Carlos III de Madrid

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From: Gábor Fekete <[email-masked]>
Date: Thu, 4 May 2006 23:05:35 +0300

Helo Marcelo and list,

> to achieve fault tolerance and has multiple interfaces all connected to
What you describe is covered by the multiple-interface scenario and it is 
mentioned in the motivation-scenario-00 draft in Section 2.

Sorry, I was not exact enough. So, again.

1. Is a host with multiple addresses on the same interface with the same
   prefix considered as multihomed?
2. Does it make sense?
3. draft-ietf-monami6-multihoming-motivation-scenario-00.txt draft should
   mention it at least with one sentence in Section 2.
4. How does draft-wakikawa-mobileip-multiplecoa-05.txt handle this case
   when the MN wants to register multiple bindings with its HoA?

Regards,
Gabor

> > draft-ietf-monami6-multihoming-motivation-scenario-00.txt Section 2
> > should at least say that this scenario just makes no sense or won't
> > really happen.
> >
> > ever happen and if yes then how
> > draft-wakikawa-mobileip-multiplecoa-05.txt handles it.
> >
> > Regards,
> > Gabor
> >

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From: marcelo bagnulo braun <[email-masked]>
Date: Fri, 5 May 2006 10:11:05 +0300

>    prefix considered as multihomed?

ok, a couple reasons why this may make sense:
- Privacy extensions (RFC3041): The host may want to generate multiple 
addresses in order to use them in different communications (or time 
frames) in order to achieve a certain level of privacy
- Different properties of the different addresses: for instance, one 
address could be a CGA while the other address has been assigned by 
dhcp (this tow things are somehow incompatible AFAICT), and for some 
reason the hosts needs both of them

maybe there are some others...

regards, marcelo

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From: Thierry Ernst <[email-masked]>
Date: Fri, 5 May 2006 10:45:10 +0200

Dear Gabor, 

Would you also take a look at 
http://www.ietf.org/internet-drafts/draft-ietf-monami6-mipv6-analysis-00.txt
(for the MIPv6 case)
and
http://www.ietf.org/internet-drafts/draft-ietf-nemo-multihoming-issues-05.txt
(for the NEMO case)

and check if that answers your concerns ?
draft-ietf-monami6-multihoming-motivation-scenario should be taken at a
much higer level whereas technical specificities are more (or less ?)
explained in the other 2 drafts.

Thierry.

-- 
Thierry ERNST, PhD
INRIA Rocquencourt Projet IMARA
+33 1 39 63 59 30

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From: Gábor Fekete <[email-masked]>
Date: Sun, 7 May 2006 16:28:10 +0300

Hi Thierry,

Please, see the inlines too!

I checked the drafts you pointed me at.
With regards to draft-ietf-nemo-multihoming-issues-05, I concentrated
when a MR or a MNN is considered multihomed.
So, I did not consider the "definition" of multihomed NEMOs in Section 1.
I found the followings.

Section 2:
  "... One thing the reader has to keep
   in mind is that in each of the following 8 cases, the MR may be
   multihomed if either (i) multiple prefixes are available (on the home
   link, or on the visited link), or (ii) the MR is equipped with
   multiple interfaces. ..."
So, basically the same as in
draft-ietf-monami6-multihoming-motivation-scenario.

Section 2.1:
  "o  The MR has multiple interfaces and thus its has multiple CoAs;

   o  Multiple global prefixes are available on the visited link, and
      thus it has multiple CoAs; or

   o  Multiple global prefixes are available on the home link, and thus
      the MR has more than one path to reach the home agent."
Aren't these 3 points meant to specify when a MR is multihomed?
If not then I think it should. But then it should be synchronized with
the above quoted part of Section 2.

Section 2.1 and others with having a single MNP:
  "Regarding MNNs, they are (usually) not multihomed since they would
   configure a single global address from the single MNP available on
   the link they are attached to."
It is not clear what "usually" means. Does it mean that they can be
multihomed even if they have a single MNP? Does it mean an MNN is
multihomed only if it has multiple interfaces, provided there is a single
MNP? What about saying:
"Regarding MNNs, they may or may not be multihomed. See [X] for the
definition of a multihomed node."

I think that MR multihoming is/should be the same as host multihoming.
Isn't it so?
And host/NEMO multihoming should be defined at one single place and clearly.

With regards to draft-ietf-monami6-mipv6-analysis-00, it does not mention
the "multiple CoAs, single prefix, single interface" case either.

Therefore, my initial question is still open.
But now I must rephrase it:

Should a host with multiple addresses with the same prefix on its single
interface be considered as multihomed?

On Friday 05 May 2006 11:45, Thierry Ernst wrote:
> http://www.ietf.org/internet-drafts/draft-ietf-monami6-mipv6-analysis-00.tx
>t (for the MIPv6 case)
> and
> http://www.ietf.org/internet-drafts/draft-ietf-nemo-multihoming-issues-05.t
>xt (for the NEMO case)
>

Which of my concerns/questions do you refer to as technical specific?
If the definition of multihoming then I must disagree.
If the multiplecoa question, then I agree, but then I don't understand
the point of your last sentence :)

Regards,
Gabor

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From: Ryuji Wakikawa <[email-masked]>
Date: Mon, 8 May 2006 22:22:17 +0900

Hi Gabor

>    when the MN wants to register multiple bindings with its HoA?

 From this draft, no extension is necessary to support this. I.e. the  
draft can support your case.
Even if the prefix is same, the address is different. The MN can  
register the addresses as distinct bindings.
This is similar to the second scenario of Section 5.1 of the draft.

regards,
ryuji

>>> the MN MUST register all its CoAs with the HA if it wants to  
>>> register
>>> multiple
>>> bindings.

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From: Gábor Fekete <[email-masked]>
Date: Mon, 8 May 2006 17:24:55 +0300

Helo Ryuji and list,

> Hi Gabor

[snip]

> register the addresses as distinct bindings.

Great!

> This is similar to the second scenario of Section 5.1 of the draft.

Similar but it does not cover this case clearly since it talks about
"multiple prefixes".

And now some non-multiplecoa related note:

I think it is quite clear what I am up to with this thread. If there is
no disagreement that multiple addresses with the same prefix on a single
interface leads to a multihoming scenario then I think the definition
of node/host multihoming should be redefined/extended. For example,

"A multihomed node is a network node that has multiple global IP addresses."

(Well, yes, it becomes quite simple in this case :)). And then it can be
spliced and splitted into HoAs, CoAs, multiple/single interface scenarios
if necessary for some kind of discussion.

If there is disagreement then I don't mind but I would like to know the
reason.

Regards,
Gabor

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From: Ryuji Wakikawa <[email-masked]>
Date: Mon, 8 May 2006 23:42:45 +0900

Hi Gabor

> Similar but it does not cover this case clearly since it talks about

right. so it's not same but "similar":-)
Anyway, the prefix difference doesn't affect the operation.

> If there is disagreement then I don't mind but I would like to know  

I'm not sure how realistic your case is. However, IPv6 does not  
prohibit assigning multiple addresses on an interface regardless of  
which prefix.
Therefore, I don't mind if we support this. From the solution point  
of view, there is no difference.

regards,
ryuji