Subject: Re: [MEXT] Home Link Detection

From: Behcet Sarikaya <[email-masked]>
Date: Wed, 19 Mar 2008 09:24:51 -0700 (PDT)

my comments at the bottom.

Regards,

Behcet

----- Original Message ----
From: Vijay Devarapalli <[email-masked]>
To: Julien Laganier <[email-masked]>
Cc: [email-masked]
Sent: Tuesday, March 18, 2008 6:04:23 PM
Subject: Re: [MEXT] Home Link Detection

Julien Laganier wrote:
> Hi Vijay,
> 
> <chair hat off>
> 
> One comment below:
> 
> on Wednesday 12 March 2008, Vijay Devarapalli wrote:
>> Folks,
>>
>> In RFC 3775 and 3963, it is assumed that the mobile node is
>> pre-configure with the home prefix. So when it sees a router
>> advertisement with the same prefix, it knows it is on the home
>> link.
> 
> When RFC 5026 is used, the MN has no pre-configured home prefix but get 
> it dynamically in the MIP6_HOME_PREFIX attribute obtained via the IKEv2 
> exchange of the bootstrapping mechanism. Then it simply behave as 
> usual, i.e., quoting you "when it sees a router advertisement with the 
> same prefix, it knows it is on the home link."

The sequence of steps when the MN boots up on the home link would be
the other way around. The MN would first boot up, setup the link and
then run IKEv2 with the home agent. Not run IKEv2 with the home agent
and then send a router solicitation on the home link to trigger a
router advertisement.

> I don't see what requires additional specification.

There is nothing that specifies that the mobile node should first
setup a the p2p link that connects it to the home agent, then run
IKEv2 from the home link and obtain the home prefix, then compare
the prefix obtained from IKEv2 with the prefix obtained from the p2p
link setup and finally conclude it is on the home link. This is not
obvious. The MIP6_HOME_PREFIX attribute was designed for home address
auto-configuration. Not for home link detection.

At the last IETF meeting (I wasn't at the meeting, but was listening
to the audio stream), we had some folks go up to the microphone and
say RFC 3775 already specifies how to detect the home link and
nothing new is needed. :)

Vijay

[behcet]
In draft-sarikaya-mext-homelink-prefix-delegation
we proposed combined operation of the home  prefix assignment with IKEv2. In view of Vijay's comments above, it would make sense to consider draft-sarikaya-mext-homelink-prefix-delegation as complementing draft-devarapalli-mext-mipv6-home-link.
Because of this, I suggest Julien to consider draft-sarikaya-mext-homelink-prefix-delegation as defining a new protocol. 
  Any comments?
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---

From: Sri Gundavelli <[email-masked]>
Date: Wed, 19 Mar 2008 09:52:36 -0700 (PDT)

Hi Vijay,

Can you please clarify few questions.

> auto-configuration. Not for home link detection.

I'm not clear on the proposal. If you can clarify few things, that
will help. But, sorry I did not go through the whole thread.

a.) What type of p2p link is this ? Can this be an IPsec link ?

b.) So, on this dynamically created link, how does the home agent
host the MN's home network prefix ? How does the HA identify the
MN ? Is there an L2 mechanism assumed for the MN identification ?

c.) Does the MN know, its establishing a p2p link with the HA ?

d.) On this link, can the home agent send a Router Advertisement ?
Will that be sufficient for the MN to detect the home ?

> nothing new is needed. :)

I did say this at the MIC. Reason, under 3775 considerations when MN
is aware of its home network prefix, the text in 3775/3963 is very
clear on how the home link is detected. I assume you are bringing
a new issue of MN not aware of its HNP, P2P links, IKE ...etc, the
proposal was not clear. May be a description of the proposal, stated
assumptions and the required solution will really help.

Regards
Sri

---

From: Vijay Devarapalli <[email-masked]>
Date: Wed, 19 Mar 2008 17:49:55 -0700

> a.) What type of p2p link is this ? Can this be an IPsec link ?

It shouldn't matter. Yes, it can be an IPsec link. As part of
the p2p link setup, the mobile node obtains the IPv6 prefix for
that p2p link.

> MN ? Is there an L2 mechanism assumed for the MN identification ?

The p2p link setup happens independently of the IKEv2 exchange
with the home agent. Both the end point of the p2p link and the
home agent are co-located. And in both cases, the MN presents
an identity (like an NAI or IMSI).

> c.) Does the MN know, its establishing a p2p link with the HA ?

No. It sets up a p2p link. Then talks to the HA. Later on it
figures out both the end points are the same, based on the home
link detection mechanism,.

> Will that be sufficient for the MN to detect the home ?

Only if the MN already knows its home prefix.

> assumptions and the required solution will really help.

I expect the home agent and home prefix allocation to happen
dynamically. The allocations could even change based on what
service the mobile node wants to access. So the mobile node is
not pre-configured with a home prefix.

draft-devarapalli-mext-mipv6-home-link-01.txt talks about this
in detail. For just the description of the home link detection
issue, please see
http://www.ietf.org/mail-archive/web/mext/current/msg00831.html

Vijay

---

From: <[email-masked]>
Date: Thu, 20 Mar 2008 19:47:12 +0100

Hi Vijay,

[snip]

> an identity (like an NAI or IMSI).

I think you cannot just assume that e.g. the endpoint of
the IPSec-based p2p link is co-located with the HA. That 
is just one deployment option.

Cheers,
	Jouni

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 21 Mar 2008 13:42:05 -0700

> is just one deployment option.

Sure, but this would mean the mobile node is not on the home
link.

If the end point that terminates the p2p link and the home
agent are not co-located, then you would need a protocol like
PMIPv6 (with the end point that terminated the p2p link link
as the MAG and the home agent as the LMA), for the mobile node
to still think it is on the home link.

Vijay

---

From: <[email-masked]>
Date: Sun, 23 Mar 2008 00:30:06 +0100

> to still think it is on the home link.

Or e.g. l2tp and similar solutions. It is then another issue
whether one would consider p2p link termination point and HA
co-located or not when they are separate physical nodes connected
via l2 tunnels. Similar deployments (in spirit) are common.

Cheers,
	JOuni