> From: Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu>
>> yeah, it *is* easier to deploy first and then later make incremental
>> modifications for scalability - if you like NAT.
> You do have to build upgrade paths into the architecture if you want it
> to last ... Making an architecture last is all about .. creating
> interfaces for the rest of the system that can be stable across drastic
> changes in technology.
But that's exactly what support of multiple addresses is - the key
architectural feature needed to make large-scale multi-homing work (within the
existing routing/entity-naming architecture, i.e. the one that IPv6 shares
with IPv4). I.e. it's the thing we need to have in the architecture to allow
the upgrade path you mention.
In thinking about this whole point of acceptance of the use of multiple
addresses, I came upon an interesting way to look at it all. It starts with
the supposition that it seems likely that one way people will do multi-homing
is to use a NAT box, and thereby restrict the knowledge of the multiple
different addresses (i.e. location-dependent "routing-names") to the border
of their system.
However, another way to look at this is to say that what they really want is
to configure their machines with only one identifier, one which is (mostly)
location-indepedent, and therefore serves mostly to identify them. They are
quite happy to then have those machines depend on another device, at the edge
of their network, to provide the location-dependent routing-names for their
machines.
At an architectural level, this is obviously basically the same as saying
that one configures machines with identities, and the machines pick up their
routing-names from devices within their network, which provide this data.
(This was pretty much exactly Mo O'Dell's enhancement on Dave Clark's basic
8+8 idea.)
So why people were and are so resistant to doing the latter is a more than a
little puzzling to me, because they are clearly happy to do effectively
exactly the same thing when a NAT box is involved.
Noel
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