Re: [EXTERNAL] Re: [atn] Embedding IP information in an IPv6 address (OMNI)

Fernando Gont <> Wed, 14 October 2020 14:47 UTC

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Subject: Re: [EXTERNAL] Re: [atn] Embedding IP information in an IPv6 address (OMNI)
To: "Templin (US), Fred L" <>, Mark Smith <>
Cc: Robert Moskowitz <>, 6man <>, "" <>
References: <> <> <> <> <> <> <>
From: Fernando Gont <>
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Date: Wed, 14 Oct 2020 10:35:59 -0300
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Hi, Fred,

On 13/10/20 17:58, Templin (US), Fred L wrote:
> Mark, see my follow-up message. There is no problem with an 
> IPv6-over-foo spec
> defining its link-local address format. Almost all of the existing 
> IPv6-over-foo specs  define an interface-specific interpretation of link-locals with a prefix 
> length (fe80::/64) that does not appear in RFC4291, and none of them update RFC4291. All 
> that is said in RFC4291 is “fe80::/10”, which does not agree with the IPv6-over-foo 
> specs. I hear your point about the BSD hack of writing data into the 54 “unused” bits 
> in memory, but I am not sympathetic to that approach when what is being offered 
> here is a brand-new interface type that does not already exist in widely-deployed
> implementations, so it is a chance for a fresh start for all 
> implementations.

Without having given a lot of thought about the context, it would seem 
to me that things like ND proxy might make addresses from one link 
visible in another.

Based on the (BSD) deployed code, if I had to do anything that would 
require using the zero bits in fe80::/64, I would probably consider 
using a different prefix altogether.

Fernando Gont
SI6 Networks
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492