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IPv6 Netowrk Device Numbering BP



* Owen DeLong

> What do you get from SIIT that you don't get from dual stack in a
> datacenter?

In no particular order:

- Single stack is much simpler than dual stack. A single stack to
configure, a single ACL to write, a single service address to monitor,
staff needs to know only a single protocol, deveopment staff needs only
develop and do QA for a single protocol, it's a single topology to
document, a single IGP to run and monitor, a single protocol to debug
and troubleshoot, one less attack vector for the bad guys, and so on. I
have a strong feeling that the reason why dual stack failed so miserably
as a transition mechanism was precisely because of the fact that it adds
significant complexity and operational overhead, compared to single stack.

- IPv4 address conservation. If you're running out of IPv4 addresses,
you cannot use dual stack, as dual stack does nothing to reduce your
dependency on IPv4 compared to single stack IPv4. With dual stack,
you'll be using (at least) one IPv4 address per server, plus a bit of
overhead due to the server LAN prefixes needing to be rounded up to the
nearest power or two (or higher if you want to accommodate for future
growth), plus overhead due to the network infrastructure. With SIIT, on
the other hand, you'll be using a single IPv4 address per publicly
available service - one /32 out of a pool, with nothing going to waste
due to aggregation, network infrastructure, and so on.

- Promotes first-class native IPv6 deployment. Not that dual stack isn't
native IPv6 too, but I do have the impression that often, IPv6 in a dual
stacked environment is a second class citizen. IPv6 might be only
partially deployed, not monitored as well as IPv4, or that there are
architectural dependencies on IPv4 in the application stack, so that you
cannot just shut off IPv4 and expect it to continue to work fine on IPv6
only. With SIIT, you get only a single, first-class, citizen - IPv6. And
it'll be the only IPv6 migration/transition/deployment project you'll
ever have to do. When the time comes to discontinue support for IPv4,
you just remove your IN A records and shut down the SIIT gateway(s),
there will be no need to touch the application stack at all.

As I said earlier, I will submit an IETF draft about the use case
shortly (it seems that the upload page is closed right now, due to the
upcoming IETF meeting), and I invite you to participate in the
discussion - hopefully, we can work together to address your technical
concerns with the solution.

I did present the use case at RIPE64, by the way - I hope you will find
these links interesting:

https://ripe64.ripe.net/archives/video/37
https://ripe64.ripe.net/presentations/67-20120417-RIPE64-The_Case_for_IPv6_Only_Data_Centres.pdf

Best regards,
-- 
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com/