1. A method of path computation across multiple domains in a communication network, the method comprising: identifying a plurality of border nodes at interfaces between a plurality of domains, each domain having at least one border node; including a path computation element at each of the plurality of border nodes of the domains, such that locations of the path computation elements are known to exist in the plurality of border nodes of the domains prior to an issuing of a path computation request; selecting a first path computation element of a first border node based on load balancing criteria between the first border node of a first domain and a third border node of the first domain; receiving a path computation request at the first border node of the first domain from a source node, the path computation request specifying the source node and a destination node; and computing by the path computation element of the first border node a shortest path across the first domain.