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

otroan@employees.org Fri, 03 March 2017 07:46 UTC

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Subject: Re: A proposal for draft-ietf-6man-rfc4291bis-07
Date: Fri, 3 Mar 2017 08:46:28 +0100
In-Reply-To: <2c0ab33b-abbe-caf1-6147-0c583d7f5d61@gmail.com>
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
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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?

> 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