Re: Embedding IP information in an IPv6 address (OMNI)

Bob Hinden <bob.hinden@gmail.com> Thu, 15 October 2020 18:33 UTC

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From: Bob Hinden <bob.hinden@gmail.com>
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Subject: Re: Embedding IP information in an IPv6 address (OMNI)
Date: Thu, 15 Oct 2020 11:33:11 -0700
In-Reply-To: <3452a374e8df4fa197eda4940cd52c35@boeing.com>
Cc: Bob Hinden <bob.hinden@gmail.com>, =?utf-8?Q?Ole_Tr=C3=B8an?= <otroan@employees.org>, IPv6 List <ipv6@ietf.org>, "atn@ietf.org" <atn@ietf.org>
To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
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> On Oct 15, 2020, at 11:14 AM, Templin (US), Fred L <Fred.L.Templin@boeing.com> wrote:
> 
> Hi Ole,
> 
>> -----Original Message-----
>> From: otroan@employees.org [mailto:otroan@employees.org]
>> Sent: Thursday, October 15, 2020 10:40 AM
>> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>
>> Cc: Philip Homburg <pch-ipv6-ietf-6@u-1.phicoh.com>om>; 6man WG <ipv6@ietf.org>rg>; atn@ietf.org
>> Subject: Re: [atn] [EXTERNAL] Re: Embedding IP information in an IPv6 address (OMNI)
>> 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.
> 
> This is rather about addressing/routing in the *overlay*.
> 
>> 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.
> 
> Per-packet - a simple bit-flip changes the address from SLA to LLA or vice-versa.

Umm, that would break the transport protocol checksum.

Bob


> 
> Thanks - Fred
> 
>> Cheers,
>> Ole=
> 
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