Abstract: A method and system for multi-domain route computation. In the invention, Path Computation Elements (PCEs) are placed in different layers and computation domains between upper and lower layer PCEs are mapped so that a computation task is divided into multiple computation tasks layer by layer and that the multi-domain route computation is finally fulfilled. The invention separates route computation from signaling and runs route computation tasks in parallel. Route establishment is done by signaling after route computation. The present invention may realize route computation based on complex Traffic Engineering (TE) constraints and enable end-to-end diverse route computation. The invention places PCEs in layers, allowing good scalability and high computation efficiency. The present invention is applicable to the Automatically Switched Optical Network (ASON) and the Multi-Protocol Label Switched Network Traffic Engineering (MPLS-TE) network.

Abstract: The present invention discloses a method for identifying node reachability, a method for identifying a link, a method for calculating a routing, and a method for disseminating node address information. In the method of the node address information dissemination, when the network is initiated, each node in the automatically switched optical network performs a node address aggregation process and an aggregation address dissemination process, and obtains and stores the aggregation address respectively. Therefore, any node in the network may judge whether the node and another node in the network are reachable to each other, and may further calculate the routing between the source and destination nodes pair. Moreover, the present invention also may determine whether any traffic engineering link in the multi-level ASON network is an external link or an internal link.