Regards
   Brian Carpenter
   http://orcid.org/0000-0001-7924-6182



On 26/03/2015 05:31, Alexandru Petrescu wrote:
> Le 24/03/2015 21:01, Brian E Carpenter a écrit :
>> On 25/03/2015 08:47, JF Tremblay wrote:
>>>
>>>> On Mar 24, 2015, at 2:00 PM, Brian E Carpenter
>>>> <[email protected]> wrote:
>>>>
>>>> [...] Make-before-break renumbering (a.k.a. planned renumbering)
>>>> is preferable but we can't rely on it. (I also try to never
>>>> forget Fred Baker's observation that there is no such thing as
>>>> renumbering: there is only numbering.)
>>>
>>> Any reference for reading (on Fred’s principle)?
>>
>> I'm not aware of a written version; it's something I've heard him
>> say more than once. Of course there is RFC 4192, but it isn't in
>> that.
> 
> Not sure what the question was but there is a stds track RFC in the 2000s 
> about IPv6 router renumbering, authored at Fermilab IIRC.

You mean RFC 2894, I think.

As is written in RFC 5887:
  "An ICMPv6 extension to allow router renumbering for IPv6 is specified
   in [RFC2894], but there appears to be little experience with it.  It
   is not mentioned as a useful mechanism by [RFC4192]."

     Brian

> 
> That has a notion of difference between numbering and renumbering.
> 
> Numbering is the initial assignment of prefixes on links.  Presumably a 
> manual operation.
> 
> Re-numbering is propagation of tuples [existing prefix, new prefix] with RAs 
> messages between routers.
> 
> This technique was used by other protocols such as Hierarchical Mobile IPv6 
> which is an RFC as well, although experimental IIRC.
> 
> This of course brings the question of what is renumbering.
> 
> Alex
> 
> 
>>
>> Brian
>>>
>>>> [...] However, Dave Taht told us recently that renumbering *is*
>>>> currently broken, and I'd like to see his list of issues. For
>>>> now, here are the issues that I see:
>>>
>>> I’ll let Dave answer for himself, but my personal experience at
>>> home currently is that it breaks quite often. As soon as the home
>>> network gets renumbered, new RAs are flooded, but no RAs are sent
>>> to de-prefer the current prefix (as specified in RFC7084 L-13).
>>> I’ve seen this happen both with 6RD and in native, with two home
>>> router vendors. I usually flap my link physically to flush old
>>> addresses.
>>>
>>> Btw, I didn’t raise this morning, but I believe smooth renumbering
>>> from an ISP is possible, at least for cable ISPs (costly, but
>>> possible). This requires support for multiple concurrent prefix
>>> delegations on home routers, which I haven’t seen yet in the wild.
>>> This requirement isn’t explicitly mentioned in RFC7084, only
>>> indirectly through the support for DHCPv6-PD (WPD-1).
>>>
>>> So on the short term, proper implementation of RFC7084 L-13 is
>>> required for smoother unplanned renumbering. For smooth planned
>>> renumbering, support for multiple concurrent PDs is required. It’s
>>> too bad that the homenet architecture doc (RFC7368 section 3.4.1)
>>> does not even mentions this possibility.
>>>
>>> JF
>>>
>>>
>>>
>>>
>>>
>>
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