Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - FE80:: means FE80::/9

Alexandre Petrescu <alexandre.petrescu@gmail.com> Wed, 08 March 2017 11:03 UTC

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Subject: Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - FE80:: means FE80::/9
To: otroan@employees.org, Mark Smith <markzzzsmith@gmail.com>
References: <CAN-Dau17q_BrUuzfvB1mLDt6p5UxYikphWaHpa8VQ2L-3kx-DA@mail.gmail.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> <7A10E8D9-02F4-4D1C-B422-86ACCAABCB38@steffann.nl> <1F674D50-1C89-444C-A617-C528951F80EC@steffann.nl> <6f2b4f35-8501-f9d8-e2f6-9e545419fb76@gmail.com> <a11c6b9b-ae5c-7c7d-a71c-cc5d8b80d047@gmail.com> <C689991E-A54D-41FB-BDE6-2BFA74B10049@employees.org> <CAO42Z2xKxe24+d_reyY1rTitA9oPy0=2QSTGSN65t5wFGx51uA@mail.gmail.com> <CAO42Z2yFuuAuEb5=mb8Jwge21nahDhy1uPq-6j7YGnTF9=uM9g@mail.gmail.com> <224F03DD-D876-4288-B48D-04D997ACBE76@employees.org> <CAO42Z2wOCe16Y5u=YNDQ9PRE5dPaEK3kvtFPnZRWOkUfKmZ2xg@mail.gmail.com> <0E14B2F8-4918-4AA0-837F-4D120FAEF17D@employees.org>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Date: Wed, 8 Mar 2017 12:03:42 +0100
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Le 08/03/2017 à 11:15, otroan@employees.org a écrit :
> Mark,
>
> [...]
>
>>> E.g. you wouldn't say the packet was sent from the source FE80::/128.
>>
>> You wouldn't say it, but you could say it, it would be correct.
>>
>> Here's an example of their equivalence.
>>
>> I assign an IPv6 address to an interface under Linux, and it shows it
>> as a /128 prefix.
>>
>> [root@opy mark]# ip -6 addr add 2001:db8::1 dev dummy0
>> [root@opy mark]# ip -6 addr show dev dummy0
>> 9: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 state UNKNOWN qlen 1000
>>    inet6 2001:db8::1/128 scope global
>>       valid_lft forever preferred_lft forever
>>    inet6 fe80::c087:1cff:fe7a:413c/64 scope link
>>       valid_lft forever preferred_lft forever
>> [root@opy mark]#
>>
>> I suppose under Linux, packets are sourced from /128s ;-)
>
> Many implementations conflate configuring an address and configuring an onlink prefix / connected route.
> That doesn't mean they are the same thing.
>
> Aren't we already far out into the weeds with this discussion?

The discussion went far indeed.

If I were to conclude:

RFC4291bis should clear the current confusion between FE80::/9, 
FE80::/10 and FE80::/64.  Keep FE80::/10 only, add statement that is not 
a /9 (despite its last set bit at position number 9), and remove 
FE80::/64 throughout.

RFC4862 should no longer say "prefix FE80::" because it is confusing. 
There is more to be fixed there, but separate discussion.

It would be good too if RFC4291bis said in a small place that "FEBF::1 
is a Link-local address too".

The fact that everybody always says "an FE80 is an LL", or "an LL is an 
FE80" does not mean FEBF::1 is not an LL too.  And that has deep 
consequences to address plans.

Alex

>
> Ole
>