Re: [v6ops] draft-anderson-v6ops-siit-dc-01

[Tore Anderson <[e-mail]>]

* Ca By <[e-mail]>

> I have read  draft-anderson-v6ops-siit-dc-01.
> 
> I support the document to be republished as a WG informational document
> with  the RFC6145 changes  moved into a new document.

Thank you!

> I have a one minor comments about draft-anderson-v6ops-siit-dc-01.
> 
> The I-D identifies a real network scaling problem where dual-stack is not
> an acceptable solution since it does not allow network operators to
> decouple IPv4 addresses from nodes deployed, thus nodes deployed cannot
> scale beyond IPv4 address holdings with dual-stack.  The IETF needs to
> provide better guidance than  "dual-stack everything".  But, the I-D does
> not address the simplest solution of simply having IPv4 nodes for IPv4
> traffic and IPv6 nodes for IPv6 traffic.  This allows a data center
> operator to get the most usage out of scarce IPv4 nodes since they pick up
> the IPv4-only users (excluding Apple happy eyeballs!!!) while the IPv6
> nodes pickup the IPv6 capable users.  Now, this approach of IPv4-only nodes
> and IPv6-only nodes works great when you are Facebook and your smallest
> unit of provisioning is a fully packed rack of gear.  If you are a smaller
> operator, you may not have enough traffic to justify an IPv6-only node, yet
> you still have to scale nodes beyond IPv4 holdings.  There is also the case
> where uniformity of provisioning is seen as being a higher value than
> having 2 flavor: v4 and v6... thus draft-anderson-v6ops-siit-dc-01
> certainly fits a need, but it should be context of dual-stack and single
> stack v4 and v6.

I'm not so sure about having separate IPv4-only and IPv6-only
infrastructures solves anything, actually...

To continue the Facebook analogy with a rack of IPv4-only frontend
nodes and another rack of IPv6-only frontend nodes that serve IPv4-only
and IPv6-capable users: Presumably all those users need to be shown the
same content, regardless of which IP version they used to request it.
So those IPv4/IPv6-only frontend racks necessarily share a common set
of backend servers - and if they're to be reachable from both the
IPv4-only and the IPv6-only frontend nodes, then the backend nodes must
necessarily be dual-stack.

So we're back to IPv4 being a limiting factor for scaling, and in my
experience the number of backend nodes usually greatly outnumber the
number of frontend nodes so really this is where you primarily would
want to avoid dual-stack. (If we're talking about Facebook or someone
of similar size, dual-stack using RFC1918 for IPv4 in the backend
doesn't necessarily scale well enough either.)

Tore