End-to end inter-domain routing

A method of constructing an end-to-end routing path from a source entity in a source domain to a destination entity in a destination domain across multiple domains supporting packet based connection oriented technologies, the method comprising the steps of:

• receiving inter-domain data from each domain-specific intra-domain path computation entity, said inter-domain data including information relating to each border element of each corresponding domain and the links between those border elements of each domain and border elements of other domains;
• generating a domains topology identifying all possible domains from said multiple domains, the border elements of those domains, and the inter-domain links among those domains;
• receiving an end-to-end path request from the source entity, said end-to-end path request including details of the destination entity of the path and any attributes required for that path;
• removing from the domains topology all domains and inter-domain links that are unlikely to be traversed in the requested path;
• generating the following for each domain remaining after the removal step:
• a virtual Domains Topology request including each of the border elements of that domain that may feature in the path and any attributes required by said path;
• sending said virtual Domains Topology requests to intra-domain path computation entities of the source domain, of the destination domain, and of all possible transit domains;
• receiving a virtual Domains Topology reply from each domain receiving corresponding virtual Domains Topology request, the virtual Domains Topology reply including logical links, each logical link representing corresponding domain-specific candidate intra-domain path and its associated attributes, wherein each candidate intra-domain path is capable of inclusion in the requested path from the source entity to the destination entity;
• determining the attributes of each inter-domain link remaining after the removal step;
• generating a virtual network topology by combining the logical links and their associated attributes with the remaining inter-domain links and their associated attributes;
• and
• determining a best end-to-end route by analyzing said virtual network topology.