Re: [v6ops] RFC6459 "IPv6 in 3GPP" - the IID in the LL address

[<[e-mail]>]

Hi Alex,

Please see inline.

Cheers,
Med

> -----Message d'origine-----
> De : Alexandre Petrescu [mailto:[e-mail]]
> Envoyé : lundi 10 juillet 2017 18:28
> À : BOUCADAIR Mohamed IMT/OLN; [e-mail]
> Objet : Re: [v6ops] RFC6459 "IPv6 in 3GPP" - the IID in the LL address
> 
> 
> 
> Le 10/07/2017 à 16:58, [e-mail] a écrit :
> > Re-,
> >
> > Please see inline.
> >
> > Cheers,
> > Med
> >
> >> -----Message d'origine-----
> >> De : Alexandre Petrescu [mailto:[e-mail]]
> >> Envoyé : lundi 10 juillet 2017 16:46
> >> À : BOUCADAIR Mohamed IMT/OLN; [e-mail]
> >> Objet : Re: [v6ops] RFC6459 "IPv6 in 3GPP" - the IID in the LL address
> >>
> >>
> >>
> >> Le 10/07/2017 à 16:16, [e-mail] a écrit :
> >>> Alex,
> >>>
> >>> I'm focusing on this part of your answer.
> >>>
> >>> Please see inline.
> >>>
> >>> Cheers, Med
> >>>
> >>>> -----Message d'origine----- De : Alexandre Petrescu
> >>>> [mailto:[e-mail]] Envoyé : lundi 10 juillet
> >>>> 2017 15:51 À : BOUCADAIR Mohamed IMT/OLN; [e-mail] Objet :
> >>>> Re: [v6ops] RFC6459 "IPv6 in 3GPP" - the IID in the LL address
> >>>>
> >>>> Med,
> >>>>
> >>>>
> >>>>>> This has consequences on privacy, and may impact
> >>>>>> interoperability when DHCPv6-PD is used later in the process.
> >>>>>
> >>>>> [Med] I don't follow you here. There is no privacy concern out
> >>>>> there. The IID used when forming a global IPv6 address will be
> >>>>> selected by the terminal; no assumption is made about those
> >>>>> bits.
> >>>>
> >>>> There is a privacy concern: if the operator enforces the UE to
> >>>> always use the network-assigned IID then that UE is trackable.
> >>>>
> >>>
> >>> [Med] I'm not sure what you mean by "trackable" in this context. If
> >>> you mean that "a UE can be identified by the network", then an UE is
> >>> always identified by the network it connects to!
> >>
> >> YEs, and I thought that is a device-specific identifier like the IMEI,
> >> not the link-local address.
> >>
> >>> At the IP level, an UE is identified by the bits of the IPv6 prefix,
> >>>   not IID bits.
> >>
> >> Well - by the IP address.
> >
> > [Med] No. I reiterate my answer: it is identified by the prefix not the
> full IPv6 address.  Policies at the network are enforced based on the
> prefix, not the full IPv6 address.
> >
> >>
> >>> Further, a network does not need IP-related information to identify
> >>> an UE.
> >>
> >> I agree, so why does it want to impose an IID to the UE?
> >
> > [Med] This is an optimization to avoid DAD.
> 
> Ok about LL, but how about the GUA?

[Med] No problem at that front either (reading from the 3GPP spec):

==
Since the GGSN guarantees that the Prefix is unique, the MS does not need to perform any Duplicate Address Detection on addresses it creates.
==

  If the network uses a GUA same as
> the UE then there should be DAD for that GUA.

[Med] Idem as above, the spec is clear: 

==
The GGSN shall not generate any globally unique IPv6 addresses for itself using the Prefix assigned to the MS in the Router Advertisement.
==

> 
> I dont think there is any spec that tells that the network MUST NOT
> assign a GUA on its interface towards the UE.

[Med] See for example, 3GPP TS. 29.061

> 
> 
> 
> >>> I still don't see any privacy concern in supplying an IID to an UE
> >>> to be used for forming its link-local address.
> >>
> >> Err...
> >>
> >> It's because the supplied IID is very much like an IEEE MAC 48bit
> >> address.
> >
> > [Med] This is a link-local address not a GUA. So, not sure to understand
> your point.
> 
> I can understand your point about GUA privacy vs LL privacy.

[Med] OK.