Abstract: A method of constructing a backup path in an autonomous system (AS) for failure of a first inter-AS link serving a first set of prefixes is described. The method comprises identifying an alternate inter-AS link serving said plurality of prefixes and constructing a tunnel thereto.

Abstract: A method of managing forwarding of data in a first autonomous system (AS) is described. The first AS includes a plurality of border routers having inter-domain links to one or more remote AS's and an associated exterior communications protocol. The border routers use an interior communications protocol with other border routers in the first AS using primary tunnels. The method comprises the steps, performed at a first border router having a primary route via an inter-domain link to a remote AS, of constructing an alternate route to the remote AS via second border router in the first AS, instigating a backup tunnel to the second border router upon failure of the primary route and sending a failure message to the other border routers.

Abstract: A technique controls distribution of reachability information for a tail-end node of a traffic engineering (TE) label switched path (LSP) to a head-end node of the TE-LSP in a computer network. The TE-LSP preferably spans multiple domains of the network such that the tail-end node resides in a domain (“tail-end domain”) that is different (remote) from the domain of the head-end node (“head-end domain”). According to the inter-domain information distribution technique, the head-end node requests the remote reachability information from the tail-end node, which may employ an Interior Gateway Protocol (IGP) to transmit the information to a border router of the tail-end domain. The tail-end domain border router then shares this information with at least a head-end domain border router. The head-end node thereafter requests that the head-end domain border router release the reachability information into the head-end domain. The head-end node uses the remote information to calculate routes, i.e.

Abstract: A method of managing routing of data elements, each having a plurality of characteristics having a respective attribute, in a data communications network, comprises: creating a flow record of data elements having common attributes for one or more tracked characteristics. The method further comprises defining said flow record as a trackable object; tracking a state change of said trackable an object; and performing a routing management step upon occurrence of a tracked state change.

Abstract: A technique performs an efficient constrained shortest path first (CSPF) optimization of Traffic Engineering (TE) Label Switched Paths (LSPs) in a computer network. The novel CSPF technique is triggered upon the detection of an event in the computer network that could create a more optimal path, such as, e.g., a new or restored network element or increased path resources. Once the novel CSPF technique is triggered, the computing node (e.g., a head-end node of the TE-LSP or a Path Computation Element, PCE) determines the set of nodes adjacent to the event, and further determines which of those adjacent nodes are within the TE-LSP (“attached nodes”). The computing node performs a CSPF computation rooted at the closest attached node to determine whether a new computed path cost is less than a current path cost (e.g., by a configurable amount), and if so, triggers optimization of the TE-LSP along the new path.

Abstract: A method of advertising repair capability in a network repair scheme using network repair addresses for repairing around a repairable network component in a data communications network having, as components, nodes and links therebetween, comprises establishing whether an alternate repair path is available around a repairable component. If such a repair path is available, the method further comprises issuing a corresponding notification to nodes in the network.

Abstract: A method is disclosed for constructing a backup route from a source node around an adjacent component. The source node derives a first set of nodes reachable from it without traversing the adjacent component and a second set of nodes from which a neighbor node of adjacent components is reachable without traversing the adjacent component. The source node then constructs a backup route via an intermediate node in the intersection of the first and second sets.

Abstract: A method and system for protecting valuable resources within an autonomous system network. Address prefixes within the system are designated as valuable and a flag bit is associated with the address within routing tables of routers of the network. Interfaces to border routers are identified and when packets are received at those interfaces, the packets are flagged with a flag or tag bit. The destination address of the received packet is compared to the flag bit associated with the valuable resource prefix, and if the packet is directed to that resource the packet is dropped and/or logged, but the packet is not forwarded to that resource. In specific cases an interface from an external source may be configured to not create the flag or tag bit, wherein that packet will be delivered to the destination prefix of the packet.

Abstract: A technique dynamically resizes Traffic Engineering (TE) Label Switched Paths (LSPs) at a head-end node of the TE-LSPs in preparation to receive redirected traffic in response to an event in a computer network. The novel dynamic TE-LSP resizing technique is based on the detection of an event in the network that could cause traffic destined for one or more other (“remote”) head-end nodes of one or more TE-LSPs to be redirected to an event-detecting (“local”) head-end node of one or more TE-LSPs. An example of such a traffic redirection event is failure of a remote head-end node or failure of any of its TE-LSPs. Specifically, the local head-end node maintains TE-LSP steady state sampling and resizing frequencies to adapt the bandwidth of its TE-LSP(s) to gradual changes in the network over time.

Abstract: A path verification protocol (PVP) which enumerates a series of messages sent to a set of nodes, or routers, along a network path identifies connectivity and transmission characteristic attributes by defining, implementing, and analyzing path verification messages (PVMs) in a VPN environment. Typical VPN environments are characterized by service level agreements (SLAs) between service providers which specify particular service level and/or bandwidth level guarantees, typically in terms of megabits per second (MB/s) or other qualitative transfer criteria. Such guarantees are often expressed in contractual terms as Quality of Service (QoS) criteria. Configurations herein provide a mechanism for determination of paths and/or routes that satisfy a QoS or other delivery speed/bandwidth guarantee. Such a mechanism may therefore be employed to perform routing decisions for QoS based traffic.

Abstract: A method of constructing a forwarding information structure for forwarding data in a data communications network comprising as components and links therebetween comprises the step, performed at a constructing node, of detecting a component change. The method further comprises the step, performed at a constructing node, of assessing the extent of a corresponding change required to an existing forwarding information structure at the constructing node.

Abstract: Various systems and methods are disclosed for performing multicast routing over unidirectional links. For example, one method involves maintaining a multicast adjacency sate, which is associated with an interface that is coupled to receive messages from a network device via a unidirectional link. The multicast adjacency state identifies a network address of the network device. The method also involves sending a multicast protocol control message to the network device via a bidirectional path. The destination address of the network multicast protocol control message is the network address in the multicast adjacency state.

Abstract: Various systems and methods are disclosed for performing multicast routing over unidirectional links. For example, one method involves maintaining a multicast adjacency state, which is associated with an interface that is coupled to receive messages from a network device via a unidirectional link. The multicast adjacency state identifies a network address of the network device. The method also involves sending a multicast protocol control message to the network device via a bidirectional path. The destination address of the network multicast protocol control message is the network address in the multicast adjacency state.

Abstract: A system and method routes data traffic over a unidirectional link of a computer network configured to implement a routing protocol, such as the ISIS routing protocol. To that end, the invention extends the ISIS routing protocol to allow dynamic discovery of neighboring routers (i.e., neighbors) that are connected via the unidirectional link and subsequent establishment of an adjacency between the neighbors over the link. Adjacency establishment is illustratively effected through the use of novel type/length/value (TLV) encoded formats appended to ISIS Hello packets to convey information between the neighbors.

Abstract: A technique dynamically triggers an exchange of reachability information between a tail-end (remote) domain target node (e.g., a tail-end node) of a traffic engineering (TE) label switched path (LSP) and a local domain head-end node of the TE-LSP in a computer network. The inter-domain information retrieval technique is illustratively based on triggering a Border Gateway Protocol (BGP) session whereby at least a portion of the reachability, i.e., routing, information of the tail-end node is transmitted to the head-end node of the TE-LSP in accordance with BGP. Specifically, once a TE-LSP is established between the head-end node and the tail-end node, the head-end node triggers the tail-end node, e.g., through extensions to a request/response signaling exchange, to establish the BGP session. Establishment of the BGP session enables transmission of the routing information from the tail-end node to the head-end node. The head-end node uses the routing information to calculate routes, i.e.

Abstract: A technique calculates a shortest path for a traffic engineering (TE) label switched path (LSP) from a head-end node in a local domain to a tail-end node of a remote domain in a computer network. The novel path calculation technique determines a set of different remote domains through which the TE-LSP may traverse to reach the tail-end node (e.g., along “domain routes”). Once the set of possible routes is determined, the head-end node sends a path computation request to one or more path computation elements (PCEs) of its local domain requesting a computed path for each domain route. Upon receiving path responses for each possible domain route, the head-end node selects the optimal (shortest) path, and establishes the TE-LSP accordingly.

Abstract: 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.

Abstract: A data communication device (e.g., a router) originates a network configuration message in response to a network topology change or so as to refresh a configuration message. The data communication device encodes a timestamp in the network configuration message. The timestamp indicates a time of originating the network configuration message. Further, the data communication device transmits the network configuration message over the network to other network devices that, in turn, initiate further broadcast of at least a portion of contents of the network configuration message. Based on the timestamp of the network configuration message, the data communication devices receiving the network configuration message identify transmission time value indicating how long the network configuration message takes to be conveyed over the network to the other network devices.

Abstract: 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.

Abstract: Customer edge (CE) to CE device verification checks initiate routes from available CEs as a set of path verification messages, destined for remote CE routes serving a remote VPN. An extended community attribute, included among the attributes of the path verification message, stores the identity of the originating CE router. The path verification message propagates across the network, and transports the identity of the originating CE router because the originator identity is not overwritten by successive routing. Upon receipt by the remote CE, the originator is determinable from the extended community attribute. A further reachability field is also included in the extended community attribute and indicates whether per CE or per prefix is appropriate for the particular route in question. In this manner, CE-CE connectivity checks identify CEs which are reachable from other CEs. Accordingly, such a mechanism allows for route reachability aggregation on a per-CE or per-prefix reachability basis.