On 3/22/15, 8:05 PM, "Ian Wells" 
<ijw.ubu...@cack.org.uk<mailto:ijw.ubu...@cack.org.uk>> wrote:

Seems to me that an address pool corresponds to a network area that you can 
route across (because routing only works over a network with unique addresses 
and that's what an address pool does for you).  We have those areas and we use 
NAT to separate them (setting aside the occasional isolated network area with 
no external connections).  But NAT doesn't separate tenants, it separates 
externally connected routers: one tenant can have many of those routers, or one 
router can be connected to networks in both tenants.  We just happen to 
frequently use the one external router per tenant model, which is why address 
pools *appear* to be one per tenant.  I think, more accurately, an external 
router should be given an address pool, and tenants have nothing to do with it.

I think conflating address pools with routable space is a mistake. To me, this 
is the concept of "address scope" which I see as distinct from pool. For 
example, a single shared routable space may have several pools, each a /8 which 
is owned by a specific tenant. This is something that I would like to see in 
Liberty, making a the concept of an address scope a first class concept. 
Routers would be able to attach only to networks within the same scope, unless 
NAT was applied.

John
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