basic algorithm is this:

* Find requesting node's control interface from the db
* Make a list of subnets the node is on, excluding the subnet on the
  control interface
* Get a list of ALL interfaces of nodes in our experiment (excluding
  interfaces with no IP). Sort by node_id, then IP address to ensure
  symmetry of LINK= numbers. Link number gets incremented for each
  interface on the remote node. The first _direct_ link
  (ie. same-subnet) to another node gets an alias.

Simple, really.