Abstract: A SONET network terminated by routers includes working paths and backup paths. The routers pre-establishes in their link state data bases the links in both for both the working and backup paths. However, the links involved in the backup paths are given higher costs, then the links working paths, that the routers select only the links in the working path. If there is a failure in a link in a working path, an APS arrangement provides rapid switchover of the optical links so as to substitute one or more links in the corresponding backup path. This is accomplished by changing the relative costs of the working and backup links involved, so that the routers select the backup links for their routing tables.

Abstract: The present invention supports the operation of IS-IS over UDLs without the need for encapsulation of IS-IS PDUs in IP and without the need for a large-scale upgrade of the protocol in the network. The present invention also supports adjacency establishment when the return path from a router at the receive end of a to the router at the transmit end of the unidirectional link is via another unidirectional link.

Abstract: In one embodiment, one or more path computation requests from path computation clients (PCCs) in a first network domain are received at a first border router (BR) arranged at the border of the first network domain and a second network domain. The first BR learns of a path computation element (PCE) in the second network domain. The PCE in the second network domain is informed of path computation information for the first network domain. One or more tunnels are established between the first BR and the PCE in the second network domain. One or more path computation requests from PCCs in the first network domain are passed from the first BR, through the one or more tunnels, to the PCE in the second network domain, to be serviced by the PCE in the second network domain using the path computation information for the first network domain.

Abstract: In one embodiment, one or more path computation requests from path computation clients (PCCs) in a first network domain are received at a first border router (BR) arranged at the border of the first network domain and a second network domain. The first BR learns of a path communication element (PCE) in the second network domain. The PCE in the second network domain is informed of path computation information for the first network domain. One or more tunnels are established between the first BR and the PCE in the second network domain. One or more path computation requests from PCCs in the first network domain are passed from the first BR, through the one or more tunnels, to the PCE in the second network domain, to be serviced by the PCE in the second network domain using the path computation information for the first network domain.

Abstract: An example embodiment of the present invention provides a process relating to the selective filtering of an LSA at a not-so-stubby-sub-area (NSSSA) border router. In one embodiment, the border router receives an LSA from another router inside the NSSSA, which might be in the access layer of the hierarchical network design model and which might use OSPF as its IGP. If the LSA is Type 1 and includes a subnet route or forwarder address, the border router floods it to its neighboring routers, regardless of whether they are inside the NSSSA. If the LSA is Type 7 and includes a host address, the border router floods it to a neighboring router if the neighboring router is inside the NSSSA, but filters the LSA if the neighboring router is outside the NSSSA, for example, in an OSPF area in the distribution layer of the hierarchical network design model.

Abstract: In one embodiment, a first path computation element (PCE) operates between first and second network domains, and is adapted to service requests from path computation clients (PCCs) in at least the first domain. In response to a backup event (e.g., failure of a second PCE), a backup PCE in the second domain may be informed of path computation information for the first domain used by the first PCE, and tunnels may be bi-directionally established between the first PCE and the backup PCE. Once the tunnels are established, the backup PCE may be advertised into the first domain, and the backup PCE may operate to load balance service requests for the first domain through the bi-directionally established tunnels.

Abstract: A method and apparatus resynchronizes a link state database (LSDB) of a non-stop forwarding (NSF) router with the LSDB of a neighboring router (“neighbor”) while maintaining an existing adjacency with the neighbor in a computer network. An out-of-band resynchronization process executes on the routers to essentially maintain the existing adjacency between the router and neighbor, rather than resetting that adjacency as defined by a conventional resynchronization approach. By keeping the adjacency “up” from the perspective of a routing protocol, such as the Open Shortest Path First routing protocol, the adjacency can be used for continued data traffic to and from the NSF router.

Abstract: In one embodiment, a first path computation element (PCE) operates between first and second network domains, and is adapted to service requests from path computation clients (PCCs) in at least the first domain. In response to a backup event (e.g., failure of a second PCE), a backup PCE in the second domain may be informed of path computation information for the first domain used by the first PCE, and tunnels may be bi-directionally established between the first PCE and the backup PCE. Once the tunnels are established, the backup PCE may be advertised into the first domain, and the backup PCE may operate to load balance service requests for the first domain through the bi-directionally established tunnels.

Abstract: An example embodiment of the present invention provides a process relating to the selective filtering of an LSA at a not-so-stubby-sub-area (NSSSA) border router. In one embodiment, the border router receives an LSA from another router inside the NSSSA, which might be in the access layer of the hierarchical network design model and which might use OSPF as its IGP. If the LSA is Type 1 and includes a subnet route or forwarder address, the border router floods it to its neighboring routers, regardless of whether they are inside the NSSSA. If the LSA is Type 7 and includes a host address, the border router floods it to a neighboring router if the neighboring router is inside the NSSSA, but filters the LSA if the neighboring router is outside the NSSSA, for example, in an OSPF area in the distribution layer of the hierarchical network design model.