I have setup the Cloud-A with 1 - [CLC+CC] and 2 - [NC] computers. I have another Cloud-B with same configuration using the Ubuntu Enterprise Cloud

Both of them working fine individually, in the same LAN.

Now if I want to add the NC of Cloud-A to CC of Cloud-B, [in case the resources of Cloud-B are exhausted] how can I make it possible ? I guess this calls for the interoperability stuff...

Could you please explain what happens exactly when we ask for instance, the direct interaction happens between the client and NC or it goes through the CLC and CC ?

What I want to say is, say there are multiple cloud providers. A user is subscribed to any one of them, say Cloud-A for IaaS. As the requirements are dynamic, all the resources of Cloud-A may get exhausted. There may be another Cloud-B which can provide the services but that Cloud-A can't ask the client to go for Cloud-B.

So if it is possible to have some co-ordination between this two providers to share resources mutually, making client fully unaware of whats going on in the background....?