Empty and loose EROs for PCE-controlled LSPs

Junos OS supports PCE-initiated and PCC-delegated label-switched paths (LSPs), two Constrained Shortest Path First computation types are introduced for computing constrained paths locally and externally. With this, a Path Computation Client (PCC) can accept an LSP path, or Explicit Route Object (ERO), that includes loose next hops (loose ERO) or does not include a path at all (empty ERO), in addition to strict EROs. With this enhancement, the existing Junos OS constrained path computation behavior and performance are leveraged, along with the other benefits of external path computing.