Abstract: A technique triggers packing of path computation requests (PCRs) for traffic engineering (TE) label switched paths (LSPs) that are sent from one or more label-switched routers (LSRs) to a path computation element (PCE) of a computer network. According to the novel technique, incoming PCRs are packed into sets in response to a certain event, and one or more TE-LSPs (paths) are computed for each PCR of a particular set based on the PCRs of that set. Specifically, the PCE detects an event in the network (“network event”) indicating that an increase in the number of incoming PCRs has occurred, or that an increase is likely to occur due to, e.g., a change in a network element. Once the net-work event has been detected, the PCE packs the incoming PCRs into configured-length sets, such as, e.g., for a specified time interval or a certain number of PCRs.

Abstract: A technique is provided for one or more network nodes to deterministically select data flows to preempt. In particular, each node employs a set of predefined rules which instructs the node as to which existing data flow should be preempted in order to admit a new high-priority data flow. The rules are precisely defined and are common to all nodes configured in accordance with the present invention. Illustratively, a network node not only selects a data flow to preempt, but additionally may identify other “fate sharing” data flows that may be preempted. As used herein, a group of data flows has a fate-sharing relationship if the application instance(s) containing the data flows functions adequately only when all the fate-shared flows are operational. In a first illustrative embodiment, after a data flow in a fate-sharing group is preempted, network nodes may safely tear down the group's remaining data flows.

Abstract: Systems and methods for computing the paths of MPLS Traffic Engineering LSPs across Autonomous System and/or area boundaries. A distributed path computation algorithm exploits multiple path computation elements (PCEs) to develop a virtual shortest path tree (VSPT) resulting in computation of an end-to-end optimal (shortest) path. In some implementations, the VSPT is computed recursively across all the Autonomous Systems and/or areas between the head-end and tail-end of the Traffic Engineering LSP.

Abstract: Load balancing enables the use of linear programming techniques to reduce the complexity of computing backup tunnel placement for guaranteed bandwidth protection. The ability to load balance among multiple backup tunnels transforms the placement problem into one that may be characterized as a series of linear constraints usable as input to a linear programming procedure such as the simplex method. Each node may compute its own backup tunnels and signal the tunnels to its neighbors with zero bandwidth to allow implicit sharing of backup bandwidth.

Abstract: Systems and methods for preemption of Traffic Engineering LSPs such that preemption decisions are made in a coordinated fashion along the path of a new LSP and computation of a new path for a preempted LSP can take advantage of knowledge of newly unavailable links. The efficiency of the preemption mechanism is greatly increased and the undesirable effects of heterogeneous preemption decisions are limited. The amount of signaling may also be significantly reduced. In one implementation, these advantages are achieved by exploiting an upstream preemption feedback mechanism that uses an incremental timer to delay preemption decisions until feedback is available.

Abstract: Load balancing among fast reroute backup tunnels in a label switched network is achieved. M backup tunnels may be used to protect N parallel paths. A single backup tunnel may protect multiple parallel paths, saving on utilization of network resources such as router state and signaling information. A single path may be protected by multiple backup tunnels, assuring that bandwidth guarantees are met under failure conditions even when no one backup tunnel with sufficient bandwidth may be found. A packing algorithm is used to associate individual label switched paths (LSPs) with individual backup tunnels. If an LSP cannot be assigned to a backup tunnel, it may be either rejected, or additional bandwidth is allocated to existing backup tunnels, or a new backup tunnel is established.

Abstract: Load balancing among fast reroute backup tunnels in a label switched network is achieved. M backup tunnels may be used to protect N parallel paths. A single backup tunnel may protect multiple parallel paths, saving on utilization of network resources such as router state and signaling information. A single path may be protected by multiple backup tunnels, assuring that bandwidth guarantees are met under failure conditions even when no one backup tunnel with sufficient bandwidth may be found. A packing algorithm is used to associate individual label switched paths (LSPs) with individual backup tunnels. If an LSP cannot be assigned to a backup tunnel, it may be either rejected, or additional bandwidth is allocated to existing backup tunnels, or a new backup tunnel is established.

Abstract: Systems and methods for distinguishing a node failure from a link failure are provided. By strengthening the assumption of independent failures, bandwidth sharing among backup tunnels protecting links and nodes of a network is facilitated as well as distributed computation of backup tunnel placement. Thus a backup tunnel overlay network can provide guaranteed bandwidth in the event of a failure.

Abstract: A virtual overlay backup network is established to provide Fast Reroute capability with guaranteed bandwidth protection to a network that employs end-to-end circuits such as label switched paths (LSPs). In some implementations, backup bandwidth is allocated from an available backup bandwidth pool, as defined herein, available on each link. Complete bandwidth protection may be provided rapidly upon detection of a failure while available backup bandwidth is shared between independent failures. In one embodiment, this is accomplished by provisioning backup tunnels to protect all links and nodes, wherein total available backup bandwidth on any link is not exceeded by the requirements of backup tunnels protecting any single node but backup tunnels protecting different nodes may share bandwidth.