Re: 64share v2

Brian E Carpenter <> Tue, 10 November 2020 23:06 UTC

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Subject: Re: 64share v2
To: Ca By <>
Cc: 6man <>
References: <> <> <>
From: Brian E Carpenter <>
Message-ID: <>
Date: Wed, 11 Nov 2020 12:06:39 +1300
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On 11-Nov-20 11:03, Ca By wrote:
> On Tue, Nov 10, 2020 at 1:49 PM Brian E Carpenter < <>> wrote:
>     On 10-Nov-20 21:10, Ca By wrote:
>     > Folks,
>     >
>     > In an effort to progress the conversation, i created a simple and rough pre-00 i-d (as ietf is not accepting submissions now) for your review and comment
>     >
>     >
>     I'm having difficulty reconciling that with what I read at:
>     If that email is correct, the 3GPP model is tightly bound to
>     the /64 boundary and to the notion of giving a single address
>     and predefined Interface ID to the UE. 
> This is not a correct summary. I believe rfc6459 describes it clearly. The ue receives an off-link  /64, the iid is simply a hint and typically not used. This is why rfc7278 works. 

Thanks for the clarification.

>     Also, since /64
>     is still fixed by the addressing architecture, and RA PIOs
>     are constrained by that architecture, I don't understand how
>     a UE can be "given a prefix such as a /56 using RA".
> The i-d is to requests the 3gpp to make a change to allow < 64 via RA

RFC 6459 says "The 3GPP network allocates each default bearer a
unique /64 prefix" but doesn't seem to explain how that prefix is
conveyed to the UE. It does say that the suggested IID is conveyed
by "layer-2 signaling". If the allocated prefix is only conveyed
by an RA/PIO there is something unconventional going on, i.e. the
UE is allowed to deduce *from the RA* that it owns the entire /64,
which is not all what applies on a conventional LAN. (Yes, I do see
how that enables RFC 7278, but this unconventional semantic is
not all obvious from RFC 6459.)

So if that's right, I think we do have a problem. If we (=IETF+3GPP)
decide to allow <64 prefixes in RA/PIO during the establishment of
a PDP context, that seems to be not only an unconventional use
of RA but also one that directly contravenes the /64 rule in the
addressing architecture.

I'm not against either of those things, but I think some very
explicit wording is needed to explain what's going on and how it
is different from a conventional LAN.


>     Perhaps someone familiar with 3GPP internals, e.g. the authors
>     of RFC6459, can comment?
>     Regards
>         Brian