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Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - interpretations of the "sum"

Fernando Gont <fgont@si6networks.com> Tue, 07 March 2017 17:11 UTC

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Subject: Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - interpretations of the "sum"
To: Sander Steffann <sander@steffann.nl>, Alexandre Petrescu <alexandre.petrescu@gmail.com>
References: <CAN-Dau17q_BrUuzfvB1mLDt6p5UxYikphWaHpa8VQ2L-3kx-DA@mail.gmail.com> <ABE47051-FBFC-460F-89B0-FFD451410F7B@google.com> <m1cjviu-0000EYC@stereo.hq.phicoh.net> <5BC57F0E-50FD-4452-853F-A08291C91EB1@google.com> <m1ck5mu-0000GaC@stereo.hq.phicoh.net> <5B4AFF50-8CA9-4134-8CE2-A383DB5F8BF5@google.com> <m1ckxfo-0000IMC@stereo.hq.phicoh.net> <225F639E-27C1-4408-BC2B-26500929049B@google.com> <CAOSSMjUR203+hYFBrFBrj9Xkjux3o7fYNd4y9kNyxwpLxF11ew@mail.gmail.com> <6D825351-7F43-4540-89AB-48DC2B5E92E3@google.com> <CAOSSMjUP6m-L1iNhE=BxHW+7hvt4YsZgxxtVn+qmgEVS9HeStA@mail.gmail.com> <CAJE_bqfpE-NWwG12S4CXM+ZnHdHHH31-y+_+pYhuCuq2FtqZ4w@mail.gmail.com> <6f532a72-a142-5d84-f351-c38cba5230d! d@gmail.c om> <5773AF65-4E7E-43B6-BCB1-26F6E9CD3C60@steffann.nl! > <fdc3fa b6-fdcb-f390-e6ea-d9e49edacf52@gmail.com> <7A10E8D9-02F4-4D1C-B422-86ACCAABCB38@steffann.nl> <b86627e7-3668-304f-f1 2e-71ad3bfd6f7a@gmail.com> <1F674D50-1C89-444C-A617-C528951F80EC@steffann.nl>
From: Fernando Gont <fgont@si6networks.com>
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On 03/07/2017 01:38 PM, Sander Steffann wrote:
> Hi,
> 
>>> In step 3 the N rightmost bits of that are overwritten with the
>>> N-bits-long IID.
>>
>> YEs, that covers the 64bit rightmost part.  But that does not say what
>> to put between /10 and /64.
> 
> Yes it does. In whatever way you read it those bits contain 0.

Fully agreed.

That aside, when you learn link-locals via some APIs in BSDs, you'll
find that some of such bits are non-zero -- that's because they leverage
the requirement for them to be zero, and use such bits to store e.g. the
interface index. (it was one of my WTH moments when coding tools :-) ).

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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