Subject: Re: I-D Action: draft-imadali-its-vinipv6-vula-00.txt

From: Brian E Carpenter <[email-masked]>
Date: Tue, 19 Feb 2013 14:56:59 +0000

> 3.3.  Examples of use
> 
>    The Mobile Router (MR) that executes the previous algorithm, is
>    capable of announcing the generated prefix on one or several internal
>    interfaces and configure one or several external interfaces,
>    depending on the scenario.  For instance, under some conditions,
>    knowing the VIN code of a vehicle, one can deduce the internally
>    advertised prefix and remotely access a well-known internal device
>    (with a certain MAC address).  This access might be possible for
>    vehicle manufacturers in order to perform remote diagnostic, or other
>    car rental companies depending on the application.
> 
>    Using the vehicle's VIN and the above method, the MR can deduce the
>    same VULA prefix and advertise it internally or use it to configure
>    its own external interfaces. 

By definition, any prefix that can be used like this is not a ULA prefix,
and has no place under fc00::/7. ULA prefixes are not to be routed externally.

> 4.1.  Method 1: RFC 4193 compliant Unique  Local IPv6 Unicast Address
>       generation
> 
>    The VIN is, according to section 3.2.2 of RFC 4193, a suitably unique
>    identifier that could be used locally to the MR for the generation of
>    an IPv6 ULA prefix and can thus be used in the algorithm described in
>    the same section.  Basically, step 2 of the aforementioned algorithm
>    is transformed in order to take the local VIN code as input.  The
>    resulting ULA prefix is advertised on MR's ingress interface, or used
>    to configure any other local interface.
> 
>    Since RFC 4193 algorithm relies on a pseudo-random generation method
>    for the ULA prefix, and introduces, for example, the timestamp at the
>    moment of the execution, two different instances of the same
>    algorithm given the same VIN code, will result in two different
>    prefixes. 

Yes. That's why, in any ULA deployment where some stability is needed,
you will only regenerate the ULA prefix in extreme circumstances
(typically a "factory reset").

...
>    Also, the VIN code is hashed and
>    partly present in the Global ID, which makes it impossible to guess
>    from a given ULA prefix.

Yes, which is a very good thing from the privacy point of view.

> 4.2.  Method 2: VIN-based Unique Local  IPv6 Unicast Address generation
> 
>    The conversion method described in Section 3.2 defines a new VULA
>    prefix format (as depicted in Figure 5) which is guaranteed unique
>    amongst the VIN-based generated prefixes.  Knowing a VIN code, it is
>    possible to derive the related ULA prefix and use this information
>    for a remote access.

This is completely unacceptable as it contradicts the most basic aspect
of ULAs: the L stands for Local.

>    This subtype of ULA prefixes which has enhanced uniqueness guarantees
>    may be defined in a separate category that requests specific /8
>    prefix (for example) that are expected to be globally routed.

Something that is globally routed or externally accessible is by definition
not a ULA.

Regards
   Brian

---

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 19 Feb 2013 16:56:33 +0100

> and has no place under fc00::/7. ULA prefixes are not to be routed externally.

ULA prefixes are not to be routed externally, as long as we're clear 
about what is external and internal.

In the vehicular communications scope, one often talks about 'inside a 
vehicle' (V) and 'outside of vehicle' (V2V or V2I).  But it's not clear 
as of yet whether two vehicles form a domain ('inside the two vehicles') 
or each vehicle is a domain in itself.

It's not clear whether the Border Router of ULAs is the same as the 
Mobile Router in vehicular context (the Router deployed in a vehicle).

The number of IP devices in one vehicle is not that large as the number 
of IP devices at a classical 'site', although several IP subnets may be 
present in one vehicle.

One may see several such neighboring vehicles to form a 'domain'.  This 
may be even truer if none is connected to infrastructure.

At that point it may be that ULAs span several vehicles.

I dont see what may forbid the use of ULAs between several vehicles. 
(although I may be wrong).

> of ULAs: the L stands for Local.

I agree.  We'll correct this.

> Something that is globally routed or externally accessible is by definition

Yes, and if I am not wrong, ULAs are globally unique.

A ULA is not globally routable.  We need to clarify this in the draft.

Alex

>
> Regards
>     Brian
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
>
>

---

From: Roger Jørgensen <[email-masked]>
Date: Tue, 19 Feb 2013 16:59:14 +0100

On Tue, Feb 19, 2013 at 4:56 PM, Alexandru Petrescu
<[email-masked]> wrote:
<snip>
> Yes, and if I am not wrong, ULAs are globally unique.

There is no guaranty that it will ever be unique, just that the chance
of a collision are quite low.

-- 

Roger Jorgensen           | ROJO9-RIPE
[email-masked]          | - IPv6 is The Key!
http://www.jorgensen.no   | [email-masked]

---

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 19 Feb 2013 17:04:19 +0100

Le 19/02/2013 16:59, Roger Jørgensen a écrit :
> <[email-masked]> wrote: <snip>
> There is no guaranty that it will ever be unique, just that the
> chance of a collision are quite low.

I agree.  The same with VINs - they are globally unique, with a
probability of collision.  There exists a paying non-IETF standard
document which requires each VIN to be unique, but implementations may
fault.

I think there is no risk of tainting one's uniqueness properties when
mapping.

Alex