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Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios

Brian E Carpenter <brian.e.carpenter@gmail.com> Thu, 21 February 2019 21:14 UTC

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Subject: Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios
To: Fernando Gont <fgont@si6networks.com>, Timothy Winters <twinters@iol.unh.edu>
Cc: IPv6 Operations <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>, "ek@loon.co" <ek@loon.co>
References: <60fabe4b-fd76-4b35-08d3-09adce43dd71@si6networks.com> <alpine.DEB.2.20.1901311236320.5601@uplift.swm.pp.se> <35adea8e-704a-76f2-857f-a83a9ad689ef@si6networks.com> <CAFU7BAS1_veTu-ZXAF0MF4niJwz149nGipx3ep_6fh1bewOzgg@mail.gmail.com> <d9503983-6524-a13a-2cb0-cdcb95f76ea6@si6networks.com> <CAFU7BAQfg712UfgW9wi9pd3eVeZP9cqJEXd6=FDmchuSdauv+g@mail.gmail.com> <82c00442-bbc4-581b-2054-2d02d50d20ad@si6networks.com> <CAFU7BASDgmSwY=SLiabSqyiTOphxU0COtFLQvT8drm0iTxM+-Q@mail.gmail.com> <76c488e0-5be7-3b81-d4c3-7af826f0dbef@si6networks.com> <CAAedzxq5d0fgOq5KZu7aCL9wxoDij6C-1Ad9+nQbYyhu2aMt-Q@mail.gmail.com> <da1c6391-5e69-f09b-dee5-83d25f1cd8cd@si6networks.com> <CAAedzxouCqcmW0rA6KwDZEO-n5yVZUYHc+GSetJ8O7=Liou4tA@mail.gmail.com> <0DDB4538-62F8-442A-A12C-D3C176540884@jisc.ac.uk> <a0a4246c-24cd-905c-4cde-0428b83ba5a3@si6networks.com> <CAOSSMjVtOXOOCHVvofsMQH5=bjV_tupqCKed6C4fXiS_ZnCSQg@mail.gmail.com> <eaea9418-cd5d-714f-9332-8b7de49d5d8b@si6networks.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Date: Fri, 22 Feb 2019 10:14:39 +1300
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On 2019-02-22 05:23, Fernando Gont wrote:
> On 21/2/19 13:14, Timothy Winters wrote:
> [...]
>>
>>     Probably an irrelevant question to ask now :-), but, anyway: any clues
>>     why RFC8028 is a "SHOULD" rather than "MUST"? -- It would seem to me you
>>     cannot really do multi-prefix without RFC8028...
>>
>> My memory of this was the working group wasn't convinced that every node
>> needed to support it.    
> 
> If you support multiple prefixes (all nodes do), then you really need
> RFC8028. Otherwise it is quite likely that you will be egress-filtered.

But as I pointed out, RFC8028 only makes rule 5.5 a SHOULD. It's
SHOULDs all the way down.

Of course, SHOULD means "that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed...". In other words, do RFC8028 and Rule 5.5
unless there's a good reason not to.

    Brian

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