Re: A proposal for draft-ietf-6man-rfc4291bis-07

Brian E Carpenter <brian.e.carpenter@gmail.com> Fri, 03 March 2017 22:05 UTC

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Subject: Re: A proposal for draft-ietf-6man-rfc4291bis-07
To: otroan@employees.org
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Sat, 4 Mar 2017 11:05:39 +1300
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On 03/03/2017 20:46, otroan@employees.org wrote:
> Brian,
> 
> [...]
> 
>>> I think that RFC 4291 bis should not retain a constraint that has been applied so far, out of convenience, in the earliest stages of IPv6 deployment.
>>
>> Agreed. And I think there are actually two things to say here:
> 
> It is of course not done because of "convenience".
> 
>> 3.1. Any IPv6-over-foo spec must specify a recommended IID length.
> 
> Why? Why and how does data-link layer type influence the recommended IID length?
> It made sense in the past when we created "modified EUI-64"s that were based on the data-link layer address, but why now?

For out-of-the-box interoperability. No other reason that I can see.

   Brian

> 
>> 3.2. In the absence of such a spec, the recommended IID length is 64 bits.
>>
>> Again, that breaks no running code, and it respects the architectural
>> statement that prefix_length + IID_length == 128, and the use of CIDR
>> routing and variable-length subnet masks.
> 
> Cheers,
> Ole
>