Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - FE80::/10 and IID length

otroan@employees.org Wed, 08 March 2017 11:35 UTC

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Subject: Re: [v6ops] A proposal for draft-ietf-6man-rfc4291bis-07 - FE80::/10 and IID length
Date: Wed, 8 Mar 2017 12:35:10 +0100
In-Reply-To: <3a1c572e-4730-1071-27b8-57999aecee5c@gmail.com>
To: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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>>> It would be good too if RFC4291bis said in a small place that
>>> "FEBF::1 is a Link-local address too".
>> 
>> No. It says the link-local prefix is FE80/10 + zeroes +
>> interface-id. If you have a 118 bit long IID you can create the above
>> link-local address, but that really does not have to be stated.
> 
> But to let that happen, it should also refrain from picturing or writing that IIDs must be of 64bit length.  If it needs to give examples it should rather use "e.g. /118".

Write an IPv6 over foo document with 118 bit IIDs.

There is a good reason the prefix-length of the link-local address space is explicitly specified.
If all nodes on a link didn't agree on this value, you would get into problems with protocols using the link-local address.
E.g. address resolution for the default router, or sending packets from DHCP server to host...

>>> 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.
>> 
>> No it hasn't.
> 
> Well...

Ole