EndpointSubset is a group of addresses with a common set of ports. The expanded set of endpoints is the Cartesian product of Addresses x Ports. For example, given:

{
  Addresses: [{"ip": "10.10.1.1"}, {"ip": "10.10.2.2"}],
  Ports:     [{"name": "a", "port": 8675}, {"name": "b", "port": 309}]
}

The resulting set of endpoints can be viewed as:

a: [ 10.10.1.1:8675, 10.10.2.2:8675 ],
b: [ 10.10.1.1:309, 10.10.2.2:309 ]