I think that the point this thread has got to is one that the multi6 WG got to a couple of years ago, and has since moved past: hence the shim6 proposal, which actually tries to deal with deployed reality (BGP, and applications that treat addresses as identifiers, for example), admits that some state is needed to deal with multihoming, and intends to ensure that this state is consistent at the two ends.
Perfect? No. Better than doing nothing? I think so. Looks rather like double-ended NAT? Yes.
Brian
Noel Chiappa wrote:
> From: Keith Moore <moore@xxxxxxxxxx>
>> 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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