摘要:
A technique efficiently selects a Path Computation Element (PCE) to compute a path between nodes of a computer network. The PCE selection technique is illustratively based on dynamic advertisements of the PCE's available path computation resources, using (i) a low-pass filter algorithm to compute such resources, and (ii) threshold determinations to control distribution of those advertisements. To that end, the novel technique enables one or more PCEs to dynamically send (advertise) their available path computation resources to a Path Computation Client (PCC) by way of the controlled advertisements. In addition, the technique enables the PCC to efficiently select a PCE (or set of PCEs) to service a path computation request based upon those available resources.
摘要:
A technique for calculating local repair paths through a computer network using one or more dynamically measured parameters in place of, or in addition to, statically assigned cost metrics. The dynamically measured parameters include various statistical measures of resources and attributes associated with data links and/or network nodes in the computer network. In operation, an intermediate node monitors a set of local link and/or node parameters. The node may generate an advertisement in response to at least one of its monitored parameters crossing a predetermined threshold value or changing value by a predetermined percentage or amount. The advertisement is “flooded” so as to advertise the dynamically measured parameter value to other neighboring intermediate nodes. After receiving the advertisement, each node may recalculate one or more local repair paths based on the advertised parameter value. The node may utilize a recalculated repair path if it provides an appreciably lower-cost path, e.g., by a predetermined percentage, as compared with the currently deployed repair path.
摘要:
In one embodiment, a loss of communication is detected between a first edge device of a computer network and a neighboring routing domain. A data packet is received at the first edge device, where the received data packet contains a destination address that is reachable via the neighboring routing domain. A determination is made whether a service label is located in a Multi-Protocol Label Switching (MPLS) label stack included in the received data packet. A service label in the MPLS label stack indicates that the received data packet was previously rerouted in accordance with fast reroute (FRR) operations. In response to a determination that the received data packet does not include a service label in the MPLS label stack, the received data packet is rerouted to a second edge device of the computer network for forwarding to the neighboring routing domain.
摘要:
A local fast reroute (FRR) technique is implemented at the edge of a computer network. In accordance with the technique, if an edge device detects a node or link failure that prevents it from communicating with a neighboring routing domain, the edge device reroutes at least some data packets addressed to that domain to a backup edge device which, in turn, forwards the packets to the neighboring domain. The rerouted packets are designated as being “protected” (i.e., rerouted) data packets before they are forwarded to the backup edge device. The backup edge device identifies protected data packets as those which contain a predetermined “service” label in their MPLS label stacks. In other words, the service label is used as an identifier for packets that have been FRR rerouted. Upon receiving a data packet containing a service label, the backup edge device is not permitted to reroute the packet a second time, e.g., in response to another inter-domain node or link failure, thereby preventing loops from developing at the edge of the network.
摘要:
A technique gracefully shuts down network resources, such as nodes, interfaces and protocols, in a data network in a manner that minimizes network disruption. The technique may be used with both connectionless and connection-oriented networking systems. A node gracefully shuts down a network resource associated with the node by i) notifying other nodes in the network that the resource is being gracefully shutdown, ii) waiting for a condition to occur, and iii) when the condition occurs, shutting down the resource. The condition may include the expiration of a predetermined amount of time and/or monitoring the resource to determine if the resource has reached a certain level of activity. In response to receiving a notification that a resource is being gracefully shutdown, a node takes action to reroute traffic around the resource. If no alternative route is available, the node may continue to route traffic to the resource until it is shut down.
摘要:
A system and method for advertising out-of-resources (OOR) conditions for entities, such as nodes, line cards and data links, in a manner that does not involve using a maximum cost to indicate the entity is “out-of-resources.” According to the technique, an OOR condition for an entity is advertised in one or more type-length-value (TLV) objects contained in an advertisement message. The advertisement message is flooded to nodes on a data network to inform them of the entity's OOR condition. Head-end nodes that process the advertisement message may use information contained in the TLV object to determine a path for a new label switched path (LSP) that does not include the entity associated with the OOR condition.
摘要:
A technique protects against failure of a network element using Multi-Topology Repair Routing (MTRR) in a computer network. According to the novel technique, a protecting node (e.g., a router) maintains Multi-Topology Routing (MTR) databases for a first topology and at least a second topology. The protecting node determines whether any acceptable repair paths are available in the first topology for a protected network element (e.g., node, link, etc.) of the first topology. If not, the protecting node may establish a repair path (e.g., for Fast ReRoute, FRR) in the second topology for the protected network element.
摘要:
In one embodiment, a node identifies a plurality of equal cost best paths to a destination, the best paths having one or more associated links. The node receives dynamic link utilization information for the associated links, and determines an amount of traffic to the destination to forward over each of the equal cost best paths, the amount being dynamically dependent upon the dynamic link utilization of the associated links for each equal cost best path.
摘要:
A technique triggers optimization of a traffic engineering (TE) label switched path (LSP) that spans multiple domains of a computer network from a head-end node of a local domain to a tail-end node of a remote domain. The technique is based on the detection of an event in the remote domain (“event domain”) that could create a more optimal TE-LSP, such as, e.g., restoration of a network element or increased available bandwidth. Specifically, a path computation element (PCE) in the event domain learns of the event and notifies other PCEs of the event through an event notification. These PCEs then flood an event notification to label switched routers (LSRs) in their respective domain. Upon receiving the notification, if an LSR has one or more TE-LSPs (or pending TE-LSPs), it responds to the PCE with an optimization request for the TE-LSPs. The PCE determines whether a particular TE-LSP may benefit from optimization based on the event domain (i.e., whether the TE-LSP uses the event domain), and processes the request accordingly.
摘要:
A technique treats a protected forwarding adjacency (FA) as a dynamic entity in that it allows a backup tunnel associated with the FA to carry traffic for the FA, when it's primary tunnel has failed, up to a predetermined amount of time. If after the predetermined amount of time has elapsed and the FA has not recovered (e.g., the primary tunnel has not been reestablished), a network topology change is automatically triggered causing the network to converge on a new network topology. By triggering the network topology change, a path that is more optimal than the path associated with the backup tunnel may be subsequently determined to carry the traffic.