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

otroan@employees.org Thu, 15 October 2020 17:39 UTC

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Subject: Re: [atn] [EXTERNAL] Re: Embedding IP information in an IPv6 address (OMNI)
From: otroan@employees.org
In-Reply-To: <21e15b4016e045618628a05c3d53c5f5@boeing.com>
Date: Thu, 15 Oct 2020 19:39:38 +0200
Cc: Philip Homburg <pch-ipv6-ietf-6@u-1.phicoh.com>, 6man WG <ipv6@ietf.org>, "atn@ietf.org" <atn@ietf.org>
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To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
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Fred,

> There are many reasons why I like what we have already, but one that I will point out
> is the ease of constructing a routable OMNI site-local address (SLA) from a non-routable
> OMNI link-local address (LLA). For an OMNI LLA such as fe80:2001:db8:1:2:: all that is
> needed to turn it into an OMNI SLA is to set bit #9 to yield fec0:2001:db8:1:2::. That is
> computationally very simple and allows a single-bit translation between LLAs and SLAs
> (to get an LLA, clear bit #9 and to get an SLA se bit #9). If instead the LLA had the
> embedded prefix in bits 64 thru 127, the translation between SLAs and LLAs would
> be much more expensive.

The use of site locals also sets limitations of addressing/routing in the underlay.
With regards to performance. Is the conversion between SLA/LLA something you do per packet?
If not, I'm unsure I see why optimising that is beneficial.

Cheers,
Ole