Re: Proposal to further clarify prefix length issues in I-D.ietf-6man-rfc4291bis

Mark Smith <markzzzsmith@gmail.com> Sat, 11 March 2017 12:10 UTC

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From: Mark Smith <markzzzsmith@gmail.com>
Date: Sat, 11 Mar 2017 23:10:23 +1100
Message-ID: <CAO42Z2wWnbJWXK-J=ZVo7CtUuSw2UgPN-xGWtqNbE42+AgovkQ@mail.gmail.com>
Subject: Re: Proposal to further clarify prefix length issues in I-D.ietf-6man-rfc4291bis
To: Philip Homburg <pch-ipv6-ietf-3@u-1.phicoh.com>
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On 11 March 2017 at 22:49, Philip Homburg
<pch-ipv6-ietf-3@u-1.phicoh.com> wrote:
>> Is there anything here that isn't covered by 5942?
>>
>> And creating an artificial separation of prefixes used for address
>> assignment (SLAAC) and prefixes used for on-link determination
>> seems fraught with dangers. E.g. from a router perspective you need
>> a connected route aka an onlink prefix for the prefix used for
>> address assignment, otherwise you have no reachability.
>
> It seems to me that RFC 5942 doesn't say a lot about stateless
> address configuration. So if we want to say something like 'the IID used
> for SLAAC should be 64 bits' then RFC 5942 is not of help.
>
> The classical example where a prefix is not onlink is NBMA networks.
> But I can imagine that once IPv4 is out of the way, people will find
> more creative uses where it helps if a prefix that is used for SLAAC is not
> onlink.

See slide 18 onwards.

https://www.slideshare.net/MarkSmith214/ipv6-ras-mostly-necessary

>
> Note that in the context of ND, onlink prefixes is mostly about host
> behavior, because routers are (in practice) not using them to configure
> what is onlink or not. Also note that hosts may consider a prefix not onlink
> whereas the router considers the prefix onlink. ND can handle that.
>
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