Subject: RE: [nemo] NEMOv4 vs DS-MIPv6

From: "Soliman, Hesham" <[email-masked]>
Date: Thu, 11 May 2006 11:41:04 -0700

> The title of the option is "IPv4 home address option", and the field 
 > name is "IPv4 Home Address".  There is a "Pref" field for 
 > prefix length. 
 >   I was confused by two things.

=> The intro of the draft states that we use "address" to refer to
both addresses and prefixes. 

 > 
 > "Pref" can be confused with "Preference", that's how I read 
 > it.  Better 
 > be named "plen" in the message diagram and fully spelled 
 > "plen - Prefix 
 > Length" in the body, or similar, to avoid confusion with 
 > "preference".

=> ok.

 > 
 > The second confusion is that it clearly suggests that the 
 > HoA is bound 
 > to MNP.  Both in NEMOv6 and NEMOv4 HoA is not bound to MNP.  
 > I suggest 
 > DS-MIPv6 doesn't bind them either.  The only place where 
 > they are bound 
 > is in soon-to-be RFC informational Home Network models (IESG queue).

=> ok. 

 > 
 > > We don't talk about MNP tables but that doesn't mean we 
 > don't support
 > > it.
 > 
 > I'm against silently supporting an essential data structure 
 > for security.

=> Fine, I'll add something to explain this. Feel free to suggest text. 

Hesham

 > 
 > When programming DS-MIPv6 on a node with IPv4 and MIP6-NEMOv6 stacks 
 > (not NEMOv4) the data structure available is the Prefix 
 > Table of NEMOv6. 
 > That contains IPv6 HoA-MNP pairs. For DS-MIPv6 to support 
 > IPv4 MNPs it 
 > should contain IPv4 HoA-MNP pairs. Or maybe IPv4-mapped IPv6 
 > addresses? 
 > What does the draft recommend to implementers with respect 
 > to this choice?
 > 
 > Alex
 > 
 >

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 11 May 2006 21:01:23 +0200

Soliman, Hesham wrote:
> 
>> The title of the option is "IPv4 home address option", and the 
>> field name is "IPv4 Home Address".  There is a "Pref" field for 
>> prefix length. I was confused by two things.
> 

Even if "address" is substituted with "prefix", this gives "IPv4 home
prefix option" and "IPv4 home prefix".  And here we actually talk about
Mobile Network Prefix.

The "home prefix" is only the prefix on the home link, not MNPs below
the MR.

>> "Pref" can be confused with "Preference", that's how I read it. 
>> Better be named "plen" in the message diagram and fully spelled 
>> "plen - Prefix Length" in the body, or similar, to avoid confusion
>>  with "preference".
> 
> => ok.

Thanks.

>> The second confusion is that it clearly suggests that the HoA is 
>> bound to MNP.  Both in NEMOv6 and NEMOv4 HoA is not bound to MNP. I
>>  suggest DS-MIPv6 doesn't bind them either.  The only place where 
>> they are bound is in soon-to-be RFC informational Home Network 
>> models (IESG queue).
> 
> => ok.

Thanks.

>> I'm against silently supporting an essential data structure for 
>> security.
> 

I suggest using IPv4-mapped IPv6 addresses in the Prefix Table whenever
the HoA of MR is an IPv4 HoA (and not simple 32bit IPv4 addresses in the
NEMOv6 Prefix Table).  I am not sure though about the IPv4 MNP.  There
seems to be no specification about how to use an IPv4 prefix in the
v4-mapped v6 form, I've checked rfc4038 (app aspects of v6 trans) and
4291 (v6 addr arch).

The confusion that may arise representing a v4 MNP in v4-mapped form is
illustrated by the following two representations saying same thing but
written completely differently:  ::ffff:1.0.0.0/8
                                  ::ffff:1.0.0.0/102.
The 8bits plen is from the v4 prefix, and 102bits plen is a v6 plen.

So, because of this IPv4 MNP issue I don't know what to put in the
DS-MIPv6 Prefix Table.

Any idea?

Alex

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 11 May 2006 12:18:58 -0700

> So, because of this IPv4 MNP issue I don't know what to put in the

we can extend the definition of Prefix Table to include
IPv4 mobile network prefixes in addition to IPv6 mobile
network prefixes. that would be the simplest.

Vijay

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 11 May 2006 21:32:19 +0200

Vijay Devarapalli wrote:
>> I suggest using IPv4-mapped IPv6 addresses in the Prefix Table
>> whenever the HoA of MR is an IPv4 HoA (and not simple 32bit IPv4
>> addresses in the NEMOv6 Prefix Table).  I am not sure though about
>> the IPv4 MNP.  There seems to be no specification about how to use
>> an IPv4 prefix in the v4-mapped v6 form, I've checked rfc4038 (app
>> aspects of v6 trans) and 4291 (v6 addr arch).
>> 
>> The confusion that may arise representing a v4 MNP in v4-mapped
>> form is illustrated by the following two representations saying
>> same thing but written completely differently:  ::ffff:1.0.0.0/8 
>> ::ffff:1.0.0.0/102. The 8bits plen is from the v4 prefix, and
>> 102bits plen is a v6 plen.
>> 
> we can extend the definition of Prefix Table to include IPv4 mobile
> network prefixes in addition to IPv6 mobile network prefixes. that
> would be the simplest.

Right, that's what we did in NEMOv4.

Alex

---

From: Keiichi SHIMA <[email-masked]>
Date: Fri, 12 May 2006 10:39:08 +0900 (JST)

From: Alexandru Petrescu <[email-masked]>
Subject: Re: [nemo] NEMOv4 vs DS-MIPv6
Date: Thu, 11 May 2006 21:01:23 +0200

> v4-mapped v6 form, I've checked rfc4038 (app aspects of v6 trans) and

If your suggestion is to write that "IPv4 MNP should be kept in
IPv4-mapped IPv6 address in IPv6 prefix tables", then I am against.
That kind of design should be implementation matter.

As Vijay said in the following mail, simply saying that the prefix
table can keep both IPv6 and IPv4 prefixes seems enough to me.

---
Keiichi SHIMA
IIJ Research Laboratory <[email-masked]>
WIDE Project <[email-masked]>

---

From: Alexandru Petrescu <[email-masked]>
Date: Fri, 12 May 2006 11:50:40 +0200

Hi Keiichi,

Keiichi SHIMA wrote:
> From: Alexandru Petrescu <[email-masked]> Subject: 
> Re: [nemo] NEMOv4 vs DS-MIPv6 Date: Thu, 11 May 2006 21:01:23 +0200
> 

It may seem as implementation matter to be left out.  However, the same
draft does not leave this out and does say that the BC may store the v4
hoa address/prefix as v4-mapped:

> - If the binding update is accepted for the IPv4 home address, the 
> home agent MUST create a binding cache entry for the IPv4 home 
> address/prefix. If a single IPv4 home address were requested, it MAY
>  be stored in the IPv4-mapped IPv6 address format.

So I thought that because the BC prefers this format (v4-mapped) maybe
the Prefix Table too.

> table can keep both IPv6 and IPv4 prefixes seems enough to me.

I agree, it's simplest to write, leaving place for implementation
interpretation.

Maybe at the minimum, it is good to specify both BC and PT that IPv4
addresses and prefixes should be stored in whatever format the
implementation finds coherent (maybe v4-mapped or maybe simple 32bit
format, bot only one).

Alex