Subject: [netlmm] question on the DHCP-PD

From: "fan zhao" <[email-masked]>
Date: Thu, 20 Nov 2008 19:59:45 -0800

Hi,

Below is the question regarding the DHCP based prefix delegation I had
on the today's mext meeting.
I also cc to the netlmm mailing list.

My question is when the MN connects to a source access network using
PMIP (or other type of network
based mobility protocol), it obtains a home network prefix. Then the
MN handovers to a target access
network (i.e. the foreign link for the MN) using the Mobile IPv6. The
handover procedure is as follows.

1) The MN obtains a care-of address from the target access network.
2) The MN discovers the home agent if it does not know.
3) The MN sets up the IPsec SA with the HA if it does not have the SA
with the HA before.
4) During the step 3), the MN requests the HNP allocated from the HA
based on RFC 4877/5026.
5) The MN realizes it is on the foreign link, then it needs to send
the BU to the HA.
Since the Mobile IPv6 BU can only register the binding between the CoA
and one single home address,
in order to register the binding between the HNP and the CoA, the MN
needs to use
the NEMO extensions, for example, by setting up the 'R' bit and using
the implicit mode.
Therefore the HNP is also used as the mobile network prefix based on
the NEMO protocol.
However, the home agent does not know the same prefix is used as the
mobile network prefix
in addition to the home network prefix. Therefore, in order for the
home agent to have the
information and set up states regarding the mobile network prefix, the
prefix delegation procedure
needs to be performed. With the DHCP based prefix delegation, the MN
requests the same HNP
in the DHCP request; however, since the HNP is already allocated to
the MN during
bootstrapping, such request may be rejected. Note that the HA can
contact a DHCP server for both
HNP and MNP assignment.

It seems to me this issue is related to the separation between the
prefix delegation and the HNP allocation.
It is not clear to me how the DHCP-PD handles the case where the HNP
is the same as the MNP.
Do I miss something? Thanks.

Sincerely,
fan
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From: "Sri Gundavelli" <[email-masked]>
Date: Sat, 22 Nov 2008 21:01:46 -0800

> I also cc to the netlmm mailing list.

Hi Fan,

The home network prefix in Proxy Mobile IPv6 is a hosted
prefix on the MN-AR link. It is NOT a delegated prefix to
the mobile node such as in NEMO. It is a prefix owned by
the mobile access gateway that is hosting that prefix. The
Proxy Mobile IPv6 protocol may be allocating a unique prefix
for each mobile, per the chosen addressing model, but the
mobile still needs to obtain one or more IPv6 addresses from
that prefix, each individually, based on the enabled address
configuration procedure. It does not by default have full
prefix range of addresses for its consumption, as in NEMO.

In the context of this handoff scenario, the mobile will
be able to send BU for the individual address(es) that it
configured in the Proxy Mobile IPv6 domain. So, the NEMO
extensions that you are referring to are not applicable here.
The mobile just needs to defend these addresses individually
and not request routing for the whole prefix. This scenario
is covered in PMIP/CMIP interactions document.

Sri

> -----Original Message-----
> From: [email-masked] 
> [mailto:[email-masked]] On Behalf Of fan zhao
> Sent: Thursday, November 20, 2008 8:00 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: [netlmm] question on the DHCP-PD
> 
> Hi,
>

---

From: "fan zhao" <[email-masked]>
Date: Mon, 24 Nov 2008 14:48:07 -0800

Hi Sri,

Thanks for your reply. Please see below.

> prefix range of addresses for its consumption, as in NEMO.
I agree with you that the home network prefix and the mobile network
prefix are two different concepts. Here the issue is that the home
network prefix may be the same as the mobile network prefix.
Please see more on this below.

> is covered in PMIP/CMIP interactions document.
I agree that the MN can send separate BUs for each IP address configured
from the home network prefix. Note that the MN may also need to set up
IPsec SAs for each IP address since the IPsec SA may be associated with
the IP address only, which results in delay during handover.
In order to reduce delay, the home network prefix needs to be registered
in the binding update with the 'R' bit set and the mobile network prefix option
is not reuqired to be included assuming the implicit mode is used.
Note that only one IPsec SA (associated with one home address) is needed
to protect this BU.

This is because different addressing models are used in PMIP and CMIP.
Folks in 3GPP SA2 have discussed this issue and agreed that the whole home
network prefix should be moved during handover.

Furthermore, regardless whether the MN performs HO between PMIP and CMIP
or not, I think this is a generic issue to the DHCP PD because the NEMO does
allow the MN to have the same home network prefix and the mobile
network prefix.
I just want to know whether the DHCP PD can handle this case.
Thanks.

Sincerely,
fan

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From: Julien Laganier <[email-masked]>
Date: Tue, 25 Nov 2008 12:54:46 +0100

Hello Fan,

On Friday 21 November 2008, fan zhao wrote:
> Hi,
>
> Below is the question regarding the DHCP based prefix delegation I
> had on the today's mext meeting.
> Since the Mobile IPv6 BU can only register the binding between the
> CoA and one single home address,

There's no need to involve NEMO. You are confusing the notion of Home 
Network Prefix with that of a NEMO Mobile Network Prefix: The Home 
Network Prefix is a prefix advertized on the Home Link (by the HA or a 
router in MIPv6 case, or a MAG in PMIPv6 case), while a NEMO Mobile 
Network Prefix is a prefix delegated to a Mobile Router and advertised 
in the Mobile Network. These are different cases.

As to your scenario above, the MN will simply register with the HA any 
of the Home Addresses it configured out of the PMIPv6 Home Network 
Prefix that was avertized to him. All of these registrations will 
contain the Care-of Address that the MN configured on the foreign link.

I do not see any issues.

--julien

---

From: "fan zhao" <[email-masked]>
Date: Tue, 25 Nov 2008 15:42:20 -0800

Hi Julien,

> in the Mobile Network. These are different cases.
I completely agree with you on this. The home agent needs to know and set
up the states for both the home network prefix and the mobile network prefix
even though they may be the same. Currently this is done during the
bootstrapping
and prefix delegation procedure separately. I was not on the last SA2 meeting
and I do not know much about discussion though the stage 2 description looks
ok to me. Note that the only way currently defined to register a
prefix during the
BU is to use the NEMO extensions.

> contain the Care-of Address that the MN configured on the foreign link.
I agree that this works. However, the issue I concern about is how the DHCP-PD
works when the home network prefix is the same as the mobile network prefix,
or more generically, when the home network prefix is the part of the mobile
network prefix. Both cases are allowed in the NEMO basic support protocol.
Note that this issue is independent from whether the MN performs HO.
When the MR powers up, e.g. on a foreign link, it performs the bootstrapping
with the HA, and obtains the home network prefix from the HA during the
IPSec SA establishement. Now the MR needs to perform the DHCP PD
to obtain the mobile network prefix. Since the home network prefix is
the same as or part of the mobile network prefix and is already allocated to
the MR before, I am not sure whether the DHCP server will reject the
request of the mobile network prefix in this case. Clarification on this
issue is much appreciated. Thanks.

Sincerely,
fan

---

From: Julien Laganier <[email-masked]>
Date: Wed, 26 Nov 2008 14:06:56 +0100

Hi Fan,

On Wednesday 26 November 2008, fan zhao wrote:
> >> My question is when the MN connects to a source access network
> >> using PMIP (or other type of network
> >> based mobility protocol), it obtains a home network prefix. Then
> >> the MN handovers to a target access
> >> network (i.e. the foreign link for the MN) using the Mobile IPv6.
> >> The handover procedure is as follows.
> >>
> >> 1) The MN obtains a care-of address from the target access
> >> network. 2) The MN discovers the home agent if it does not know.
> >> 3) The MN sets up the IPsec SA with the HA if it does not have the
> >> SA with the HA before.
> >> 4) During the step 3), the MN requests the HNP allocated from the
> >> HA based on RFC 4877/5026.
> >> 5) The MN realizes it is on the foreign link, then it needs to
> >> send the BU to the HA.
> >> in order to register the binding between the HNP and the CoA, the
> >> MN needs to use
> >> the NEMO extensions, for example, by setting up the 'R' bit and
> >> using the implicit mode.
> >
> > There's no need to involve NEMO. You are confusing the notion of
> > Home Network Prefix with that of a NEMO Mobile Network Prefix: The
> > Home Network Prefix is a prefix advertized on the Home Link (by the
> > HA or a router in MIPv6 case, or a MAG in PMIPv6 case), while a
> > NEMO Mobile Network Prefix is a prefix delegated to a Mobile Router
> > and advertised in the Mobile Network. These are different cases.
>
> I completely agree with you on this. The home agent needs to know and
> set up the states for both the home network prefix and the mobile
> network prefix even though they may be the same. 

The whole point is: The case where the Home Network Prefix and the 
Mobile Network Prefix are the same doesn't make any sense in the 
context of NEMO.

The Home Network Prefix is advertized and used on the point-to-point 
link between the MAG and the MN - or MR in the case we're discussing.

If the Mobile Network Prefix is the same as the Home Network Prefix, it 
can't be advertized or used on a different link than the point-to-point 
link between the MAG and the MN/MR - otherwise you get what's called a 
multilink subnet and that is not allowed.

Thus if the Mobile Network Prefix and the Home Network Prefix are the 
same, the Mobile Network Prefix must only be advertized and used on the 
point-to-point link bewteen MAG and MN/MR.

Since the point-to-point link has only two nodes attached to it, the MAG 
and the MN/MR, given that MAG isn't mobile, you end up with a Mobile 
Network Prefix that is only advertized to and used by a single node, 
i.e. the MN/MR.

In that situation you obviously don't need to use NEMO since MIPv6 & 
PMIPv6 handle quite well the mobility of a single node - the MN.

--julien

---

From: "fan zhao" <[email-masked]>
Date: Wed, 26 Nov 2008 11:59:10 -0800

Hi Julien,

Thanks. Please see below.

> link between the MAG and the MN - or MR in the case we're discussing.
That is correct in the PMIP domain. However, when the MN handovers to
a foreign access network with the MIP used, the Home Network Prefix can
be associated with the MN's logical/physical interface, right?
Note that the case what I talked about is that a plain mobile IP terminal
(not a MR) handovers between the PMIP and CMIP access network.

> multilink subnet and that is not allowed.
I agree that when the MN attaches to the PMIP domain, it cannot advertise
the same prefix on another link. However, in the case we are discussing, the
MN performs HO from the PMIP domain, the MAG detects that and stops
advertising the Home network prefix on the P2P link, the MN configures
a care-of
address on one interface and continues to use the Home network prefix.
I do not see any issue with that.

> point-to-point link bewteen MAG and MN/MR.
I am not considering the case when the MR attaches to the PMIP domain.
In fact, I do not think any NEMO extension is needed when the _MN_ attaches
to the PMIP domain. What I concern is that the behavior of the MN when
it handovers to the target access using MIP. I mentioned the PMIP in the
example just because with the PMIP protocol, multiple IP addresses can
be configured from the home network prefix therefore, there is a need to
perserve the whole IP prefix during HO. The NEMO extension is the only
way to register a prefix with the HA. Such prefix is the mobile network prefix
and the prefix delegation needs to be performed. That is why I raised
the problem regarding the DHCP PD.

Another way to allow the whole prefix to be registered during BU is to use
the Home Network Prefix option defined in 8.3 of RFC 5213. This can be
documented in the RFC 3775bis. What do you think?
With this approach, the NEMO extensions are not needed.

However, the question regarding the DHCP PD still needs to be discussed.
Let us consider the case of initial attach, not the handover.
When the MR powers up on a foreign link, it performs the bootstrapping and
obtains a home prefix (A:B:C:0::/64) based on rfc 5026 during the IKE
and configures
a home address from that home prefix. Based on the NEMO basic support
protocol, the home address/prefix can be part of the mobile network prefix
(e.g. A:B:C::/48). The MR then runs DHCP PD to request such mobile network
prefix; however since the HA already allocates part of the mobile network prefix
(A:B:C:0::/64) to the MR during bootstrapping, the DHCP server will reject
such request, right? Do I understand correctly? What do you think? Thanks.

Sincerely,
fan