Re: Objection to draft-ietf-6man-rfc4291bis-07.txt

Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 01 March 2017 21:20 UTC

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Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt
To: Alexandre Petrescu <alexandre.petrescu@gmail.com>, =?UTF-8?Q?Dan_L=c3=bcdtke?= <mail@danrl.com>
References: <20170223134026.GI5069@gir.theapt.org> <F7C230DE-4759-4B78-ABF2-6799F85B3C62@google.com> <58B014F6.2040400@foobar.org> <6DA95097-8730-4353-A0C9-3EB4719EA891@google.com> <CAN-Dau0s04c=RV0Y8AGaxBPFui41TWPTB+5o0K2Lj-iah0An1w@mail.gmail.com> <CAL9jLaYirty22iGiEjEaYq3_KA1FZhxBTOBWuFOXQ9C-WPd5xQ@mail.gmail.com> <CAN-Dau0n6oFm538XdJOcuO1yg92BCDD3mBu5YfBVm_+g-gtcKA@mail.gmail.com> <CAL9jLaYO=uYgVfSZ0SoSe0SujJ1xgwEKE8WLzo_keJHywgXTtg@mail.gmail.com> <CAN-Dau1vJV5O_Ythp6THkAu4-YZXV82Upny1V+ybbjCVZQQX=A@mail.gmail.com> <27cce319-18ac-5c0e-3497-af92344f0062@gmail.com> <de4988be-6031-08d9-84ce-21c3fa4f9bc9@gmail.com> <98401ef7-cf41-b4a0-4d11-a7d840181bd0@gmail.com> <1047f5fc-ae40-be52-6bab-27f31fe5e045@gmail.com> <9a94feac-8d59-b153-d41c-04fc371e4db4@gmail.com> <CAO42Z2z7v4gDk91b6Of-1sczV88m3B9kzn0MeJU_VBJ416k6Ww@mail.gmail.com> <ae35b45a-0398-840f-fc0d-1f64dd2fcc58@gmail.com> <92160C59-79EC-4EB0-BFD5-69697A5E1306@danrl.com> <f1ce0d13-efee-4be0-290d-f81e9ca9e6f5@gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Thu, 2 Mar 2017 10:20:28 +1300
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On 02/03/2017 08:47, Alexandre Petrescu wrote:
> 
> 
> Le 01/03/2017 à 12:23, Dan Lüdtke a écrit :
>>
>>> On 28 Feb 2017, at 13:04, Alexandre Petrescu <alexandre.petrescu@gmail.com>; wrote:
>>>
>>> Finally, there is no advice of what bits to put between fe80:: and a
>>> 64bit the Interface ID - zeros or ones?  linux says it's a fe80::/64 and
>>> IIRC BSD says it's a fe80::/10.  The routing entries based on that can
>>> make for interop problems.
>>
>> I think there is advice. As I understand, /10 is reserved but only /64 is specified.
> 
> Sorry, I dont understand that?
> 
> What is the difference?  Why reserving X if only specifying Y?  What 
> other concept is similar: is there some other number which is reserved 
> and only number+1 is specified?
> 
> Why couldnt we just reserve without specifying?  Or specifying without 
> reserving?
> 
> If we continue with reserving _and_ specifying we continue wasting these 
> 54bits there.
> 
> What are these 54bits for?

Nothing. They are reserved and must be zero. That's quite common in 
protocol design.

Link-local is a special case, because it must be possible to create
an address with absolutely no prior information.

    Brian

> 
> Alex
> 
>>
>>
>> RFC 4291 IP Version 6 Addressing Architecture
>>   2.5.6.  Link-Local IPv6 Unicast Addresses
>>
>>      Link-Local addresses are for use on a single link.  Link-Local
>>      addresses have the following format:
>>
>>      |   10     |
>>      |  bits    |         54 bits         |          64 bits           |
>>      +----------+-------------------------+----------------------------+
>>      |1111111010|           0             |       interface ID         |
>>      +----------+-------------------------+----------------------------+
>>
>>
>> Cheers,
>>
>> Dan
>>
> 
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