Subject: [nemo] Behavior of HA

From: MATSUMOTO Taisuke <[email-masked]>
Date: Wed, 05 Nov 2003 12:22:04 +0000

Dear NEMO WG members,

I'm trying to implement the NEMO protocol stack, and I find a 
problem.

I set up my test network according to the figure 1 in the basic 
support draft page 28. See below.

  +-------------------+ 3:: 2+-------+
  |     Internet      |------| CN_MR |
  +-------------------+      +-------+
          4::      |
                   |
    2+-------------+3
  +--+-+       +---+---+
  | MR |       | HA_MR |
  +--+-+       +-------+
 5:: |1
 ----------
     2| 
   +--+-+
   | LFN|
   +--+-+

I tried to run the MR in the explicit prefix length mode. When 
the mobile router was attached to the foreign link, the MR tried 
to send the binding update message which consists of '5::1' for 
the home address and '64' for the prefix length.

But the HA rejected that BU message and returned the BA message 
with the status code 132. This behavior is defined in the section 
10.3.1 of the mobile IPv6 draft, draft-ietf-mobileip-ipv6-24.txt.

The explicit prefix length mode uses the IP address of the ingress 
interface as the home address of the mobile router. In this case, 
the IP address of the ingress interface is not an on-link IP 
address of the HA.

So, I think that some schemes to avoid that restriction of the 
mobile IPv6 specifications is required for the NEMO basic support.

Best regards,
Taisuke MATSUMOTO

---

From: Vijay Devarapalli <[email-masked]>
Date: Wed, 05 Nov 2003 12:07:50 -0800

hi,

thanks for catching this.

> support draft page 28. See below.

yes. the mobile IPv6 restriction needs to be relaxed. currently
section 10.3.1 of MIPv6 says

       if the home address for the binding (the Home Address field
       in the packet's Home Address option) is not an on-link IPv6
       address with respect to the home agent's current Prefix List, then
       the home agent MUST reject the Binding Update and SHOULD return a
       Binding Acknowledgement to the mobile node, in which the Status
       field is set to 132 (not home subnet).

for Nemo, the Home Agent should not reject the Binding if the
home address is from a prefix that has been delegated to a
Mobile Router.

comments?

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Wed, 05 Nov 2003 12:07:50 -0800

hi,

comments?

Vijay

---

From: Chan-Wah NG <[email-masked]>
Date: Thu, 06 Nov 2003 12:16:03 +0800

> home address is from a prefix that has been delegated to a

So that means for a HA with NEMO functionality, the HA after checking
the HoA, found out that the HoA is not an on-link IPv6 address, will
(instead of rejecting the BU as per a 'classical' MIPv6 HA does) go on
to check if the HoA belongs to a MR, and accept it if it is, and reject
it otherwise?

Some descriptions must be added to the section 6.

/rgds
/cwng

---

From: Chan-Wah NG <[email-masked]>
Date: Thu, 06 Nov 2003 12:16:03 +0800

/rgds
/cwng

---

From: MATSUMOTO Taisuke <[email-masked]>
Date: Thu, 06 Nov 2003 09:46:25 +0000

Hi Vijay,

Thank you for your response.

> home address is from a prefix that has been delegated to a

I think that your comment is reasonabie. But I have another 
question how to know if the prefix is delegated to the mobile 
router. If it should be pre-configured in the home agent, it makes 
the explicit prefix length mode lose an advantage to the implicit 
mode.

Am I misunderstanding anything? 

Taisuke

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 13:40:08 -0800

> the explicit prefix length mode lose an advantage to the implicit 

looks like what I suggested earlier might not be a good idea at all.
instead, here is another proposal.

    Mobile IPv6 specifies that the Home Agent should reject a Binding
    Update if the home address in the received Binding Update is not
    an on-link IPv6 address with respect to the prefixes being
    advertised on the home link. This document relaxes this restriction
    so that the Home Agent should reject the Binding Update only if the
    home address does not belong to the home prefix that the Home Agent
    is serving.

this is more generic. the Home Agent knows the home prefix that it is
serving. if the Mobile Network Prefix is a subset of this prefix, then
the Home Agent should accept binding updates from addresses configured
from the Mobile Network Prefix. the Home Agent has to just verfiy that
the home address belongs to the prefix it is serving.

comments?

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 13:40:08 -0800

comments?

Vijay

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 06 Nov 2003 23:54:50 +0100

Vijay Devarapalli wrote:
>>> if the home address for the binding (the Home Address field in 
>>> the packet's Home Address option) is not an on-link IPv6 address 
>>> with respect to the home agent's current Prefix List, then the 
>>> home agent MUST reject the Binding Update and SHOULD return a 
>>> home address is from a prefix that has been delegated to a Mobile
>>>  Router.
>>> 
>> 
> Update if the home address in the received Binding Update is not an 
> on-link IPv6 address with respect to the prefixes being advertised on
>  the home link. This document relaxes this restriction so that the 
> Home Agent should reject the Binding Update only if the home address 
> does not belong to the home prefix that the Home Agent is serving.
> 
>  serving. if the Mobile Network Prefix is a subset of this prefix, 
> then the Home Agent should accept binding updates from addresses 
> configured from the Mobile Network Prefix. the Home Agent has to just
>  verfiy that the home address belongs to the prefix it is serving.
> 
> comments?

Sure, here's my try.

If you do the last paragraph, that in explicit prefix len mode the MNP's
below a HA MUST be part of the home network prefix.  Or there exist
deployments where the MNP inside a moving network is related in no way
to the prefixes of the home link.  Agree these are not respecting the
aggregation recommentation but that recommendation is just a
recommendation, not enforced by anything else.  I guess NEMO can't
enforce the aggregation recommendation either.

With implicit and explicit network modes, MNP's can be totally different
than the home link prefix.

Alex
GBU

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 06 Nov 2003 23:54:50 +0100

Sure, here's my try.

Alex
GBU

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 15:12:57 -0800

Alexandru Petrescu wrote:

> below a HA MUST be part of the home network prefix.  

right. I didnt say prefixes advertised on the home link. MIPv6 is
specific. it says prefixes advertised on the home link. for Nemo
we relax it a bit so that the home address belongs to the home
prefix that the HA is serving. if the HA is configured to serve
a prefix that is not advertised on the home link, it should accept
binding updates for addresses configured from that prefix.

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 15:12:57 -0800

Vijay

---

From: Alexandru Petrescu <[email-masked]>
Date: Fri, 07 Nov 2003 00:36:13 +0100

Vijay Devarapalli wrote:
>>> looks like what I suggested earlier might not be a good idea at 
>>> all. instead, here is another proposal.
>>> 
>>> advertised on the home link. This document relaxes this 
>>> restriction so that the Home Agent should reject the Binding 
>>> Update only if the home address does not belong to the home 
>>> prefix that the Home Agent is serving.
>>> 
>>> this is more generic. the Home Agent knows the home prefix that 
>>> it is serving. if the Mobile Network Prefix is a subset of this 
>>> prefix, then the Home Agent should accept binding updates from 
>>> addresses configured from the Mobile Network Prefix. the Home 
>>> Agent has to just verfiy that the home address belongs to the 
>>> prefix it is serving.
>>> 
>>> comments?
>> 
>> 
>> 
>> Sure, here's my try.
>> 
>> If you do the last paragraph, that in explicit prefix len mode the
>>  MNP's below a HA MUST be part of the home network prefix.
> 
> 
> specific. it says prefixes advertised on the home link. for Nemo we 
> relax it a bit so that the home address belongs to the home prefix 
> that the HA is serving. if the HA is configured to serve a prefix 
> that is not advertised on the home link, it should accept binding 
> updates for addresses configured from that prefix.

That sounds good.  (if you didn't name this MNP a "home prefix").

Before accepting that BU, HA could also fully check the received HoA 
against the next hop field of the MNP rt entry (not only the prefixlen 
bits match of the HoA and the MNP).

Alex

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 07 Nov 2003 00:36:13 +0100

Alex