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

[<[e-mail]>]

Alex, 

The key part is not to use (or not) a GUA, but ...

The GGSN shall not generate any globally unique IPv6 addresses for
itself using the Prefix assigned to the MS in the Router
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^     
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Cheers,
Med

> -----Message d'origine-----
> De : Alexandre Petrescu [mailto:[e-mail]]
> Envoyé : mercredi 12 juillet 2017 13:42
> À : BOUCADAIR Mohamed IMT/OLN; [e-mail]
> Objet : Re: [v6ops] RFC6459 "IPv6 in 3GPP" - the IID in the LL address and
> GUA
> 
> Med,
> 
> [...]
> >>>>> 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 think that spec is wrong (3GPP TS. 29.061?).
> 
> Because, in practice some operator on some APN puts a GUA (not an LLA)
> on its router's interface towards the UE.  It uses that GUA in the src
> of the RA sent to the UE.  Packet dump available upon request.
> 
> Alex
> 
> >
> >>
> >> 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.
> >