Based on discussion w/ Greg... I think there are three approaches to this and we need to choose one. 1) treat IP as an object and make it restful 2) treat allocate_ip/deallocate_ip as methods on network+node and make them posts 3) create a "ip_enabled" method that does a post to allocate and delete to de_allocate.
After discussion, I'm ok with any of them.  Greg has a preference for #2 and I'll support that.

HOWEVER - I do have a comment about the URI pattern.  Our URI pattern has been to preceed IDs with the type of object that the ID applies to.  For example ... /nodes/node_id ... and /networks/net_id ...  This pattern makes it easier to figure out the API by inspection.

Also, the API ordering would be network/proposal_id/networks/network_id/node/node_id/allocate_ip to match this pattern.