RE: there should be a ULA prefix?? [was: A common problem with SLAAC in "renumbering" scenarios]

["STARK, BARBARA H" <[e-mail]>]

> > >>> Some time in the past, the thinking changed and now there should be a
> > ULA
> > >>> prefix in addition to any global prefixes.
> > >>
> > >> Really? Where do you think that is stated?
> > >>
> > >> I happen to run my CPE with ULA enabled, but I'm not aware of any
> > >> recommendation to do so..
> > >>
> > >
> > > RFC7084. Was also in its ancestor.
> >
> > Not so. All it says is:
> >
> >    ULA-1:  The IPv6 CE router SHOULD be capable of generating a ULA
> >            prefix [RFC4193].
>
> That could be interpreted to mean if it is capable of generating a ULA then
> it should generate and announce one. It's probably a bit of ambiguity in
> what generate can mean - generate could mean generate without
> using/announcing it, but what would be the point of doing so?

FWIW, "SHOULD be capable of doing X" is clearly different from "SHOULD
be doing X" to me: the former means it SHOULD be implemented; the
latter means it SHOULD be (implemented and) enabled.  I often see
phrases like this in IETF documents and I always interpret them this
way without seeing any ambiguity.

So I agree with Brian here.
I agree with Tatuya and Brain on how the SHOULD is interpreted.  In this case of the 7084 IPv6 Ready CE Router Logo <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ipv6ready.org_db_index.php_public_search_-3Fl-3D-26c-3D-26ds-3D-26de-3D-26pc-3D-26ap-3D-26oem-3D-26etc-3DE-26fw-3D-26vn-3D-26do-3D1-26o-3D4&d=DwMFaQ&c=LFYZ-o9_HUMeMTSQicvjIg&r=LoGzhC-8sc8SY8Tq4vrfog&m=N95yCPLb_SZCOaNyLVGMhtzt_ePCy8G9yxx51PyWSEk&s=XqtrT2N55_1szs6ez9bolqEd5d2t2N0EWWUDxqA7lNs&e=> will allow ULA to be optional, and none of the current Logos have ever claimed support for ULAs.   Taking a quick survey of about ten off-shelf Home Gateways (purchased in the US) we found that none had ULAs enabled by default.

<bhs> This is also consistent with my intent. I’ve found over the years that different ISPs want different defaults in their procured CE routers. So in BBF we quickly abandoned combining requirements for what functionality needs to be supported with default configuration recommendations. If someone wanted to see about maybe having a BCP for default configuration for specific use cases in IETF, that might be reasonable. But it’s important to scope default configuration recommendations very tightly. - Barbara