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

[Mark Smith <[e-mail]>]

On 10 July 2017 at 20:11, Alexandre Petrescu
<[e-mail]> wrote:
> Hi,
>
> The INFORMATIONAL RFC6459 "IPv6 in 3GPP" contains this paragraph:
>>
>> The 3GPP network allocates each default bearer a unique /64 prefix, and
>> uses layer-2 signaling to suggest to the UE an Interface Identifier that is
>> guaranteed not to conflict with the gateway's Interface Identifier.  The UE
>> must configure its link-local address using this Interface Identifier.
>
>
> I disagree that the UE must configure its LL using this IID.  Where is
> this requirement from?
>
> The UE should be allowed to form an IID at its will, if so it wishes.
>
> This has consequences on privacy, and may impact interoperability when
> DHCPv6-PD is used later in the process.
>
> Also, this being an INFORMATIONAL document, in no case a party
> implementing it could impose it on some other party.
>

I think the reason why it is INFORMATIONAL is that this is not an IETF
document on how to do IPv6, rather, it is the 3GPPs specification on
how to do IPv6 on their devices.

I think the IETF and the 3GPP's device models are different.

The IETF considers hosts and links to be separate things, so
supporting a new link type means no more than an IPv6-over-link RFC
that provides the required functionality to run IPv6 using generic
next layer up mechanisms. In the IETF model, there would be an
IPv6-over-3G RFC that resembled the IPv6 over PPP, IPv6 over Ethernet
etc. RFCs. After that, standard IPv6 mechanisms would be used to
bootstrap over the 3G link e.g., RAs, DHCPv6-PD etc.

3GPP seem to conflate hosts and links, and seem to be whole of device
generation or release oriented, rather than being piecemeal and
evolving feature and negotiated capability oriented that the IETF are.
As you've found they're much more prescriptive about device
capabilities and behaviours that occur higher in the stack than just
what is necessary to get IPv6 over the 3G link running.

The 3GPP model creates constraints that then have to be worked around
e.g., RFC7278, "Extending an IPv6 /64 Prefix from a Third Generation
Partnership Project (3GPP) Mobile Interface to a LAN Link".


Regards,
Mark.