graceful renumbering of CPE networks

Michael Richardson <mcr+ietf@sandelman.ca> Wed, 20 February 2019 15:25 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: 6man WG <ipv6@ietf.org>
Subject: graceful renumbering of CPE networks
In-Reply-To: <CAKD1Yr1fv3pUevB_zeZpQ-UQcNUo2zHUH4xj9NXYohyMbUSgRQ@mail.gmail.com>
References: <60fabe4b-fd76-4b35-08d3-09adce43dd71@si6networks.com> <65DB4854-97D2-4C31-A691-2CD93812EF93@consulintel.es> <CAHL_VyCMpCcGkEQu+RV1GRf2QLB-HD0+AOOBV0YhfQ5sbydVzQ@mail.gmail.com> <8CE7A0CD-97D9-46A0-814D-CAF8788F9964@consulintel.es> <e3e0bf2273e04f15b792665d0f66dfe5@boeing.com> <4c5fab33-2bff-e5b5-fc1d-8f60a01a146d@go6.si> <b4525832-9151-20bf-7136-31d87ba6c88d@huitema.net> <463f15cf-2754-e2e8-609d-dc0f33448c6c@go6.si> <ff649810-7242-7bc2-d36f-3f998f7bdd71@asgard.org> <9CDF41CA-83B4-4FC4-B995-EF79727C5458@steffann.nl> <CAO42Z2wA+vLmU7+sU6xLK7TO6pWfNQA5shs9zp=PqANCihLmBQ@mail.gmail.com> <BAB3061A-1808-4C0E-AA1B-2D7DD5BA63FC@employees.org> <bbd8b761-403a-5b3f-3f04-dc3bfdea116e@foobar.org> <6F3036C6-50A1-43C6-B554-31293B69E59D@employees.org> <433607c1-dbc6-a42e-cb17-dc209e33bdaa@si6networks.com> <12EA4FAE-BE3D-4CFE-9837-DF052F79A998@employees.org> <F48A816A-983E-4375-834C-75F103DCEA6A@employees.org> <8c8a79cf-0a87-15bc-bd91-bd2da82fdfa1@si6networks.com> <9BE77D1D-C247-4B8E-B9A F-22BE1DC9F79D@employees.org> <CAKD1Yr1fv3pUevB_zeZpQ-UQcNUo2zHUH4xj9NXYohyMbUSgRQ@mail.gmail.com>
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Date: Wed, 20 Feb 2019 10:25:40 -0500
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Lorenzo Colitti <lorenzo=40google.com@dmarc.ietf.org> wrote:
    > FWIW, I think the reason that the only way to renumber IPv6 networks is
    > (mostly) there is no way to explicitly communicate the user prefixes from the
    > CPE to the network. I think most deployments inject routes based on DHCPv6 PD
    > snooping, and the implementations of that generally only support one injected
    > route per DHCPv6 client.

on the specific comment:
  BMG (PPPoE) devices usually terminate the DHCPv6 at the BMG, and so the BMG
  sees the radius packets that went into forming the PD, so it's not DHCPv6 PD
  snooping, exactly.  There is nothing in PD or radius that prevents multiple
  prefixes from being delegated, it's just a software problem :-)
  For the cable-modem situation, the scenario is very different.

I was confused at first by your comment, so I read it a few times.
I think you are suggesting that if we could have multiple prefixes (the old
and the new), that the renumbering event would no longer be a flash
renumbering.  That the mode of operation that 7084 recommends essentially
results in flash renumbering.  There is no apparent way to introduce a new
prefix while the old prefix is still alive.

The lack of old/new prefix definitely seems like a bug and it looks like
something that 6man ought to fix with an update to 7084, ideally in a
standards track document.

    > On Wed, Feb 20, 2019 at 4:46 PM Ole Troan <otroan@employees.org> wrote:

    > Top posting. Two points here.

    > 1) Flash renumbering breaks stuff. Especially for people running servers.
    > Allowing people to host and own their own content in their own networks
    > would do a lot more to protect people’s privacy rather than changing
    > addresses. So let’s agree that the problem you want to solve is a
    > misconfiguration/error case, not recommended operational practice.

    > 2) We should always strive to make mechanisms more robust. Your suggested
    > point solution already have alternative broader solutions. E.g. MPMH host
    > or added rules in SAS. It might be worth looking at the more general
    > problem.

    > Ole

--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-