Abstract: A network element that acts as a hub in a hub and spoke topology is configured to limit the amount of topology and reachability information that is advertised to a set of one or more remote network elements that act as one or more spokes in the hub and spoke topology in a same routing area. The network element generates a set of one or two link state advertisements (LSAs) to advertise over an interface that connects at least one of the set of remote network elements to the network element, wherein the set of LSAs includes information that describes a connection to the set of remote network elements and one or more aggregate routes. The network element advertises, during a database exchange process with the one of the set of remote network elements, the set of LSAs to the one of the set of remote network elements.

Abstract: A method is implemented by a network device in a network having a plurality of nodes. The method computes a remote loop free alternative (RLFA) next hop as a backup for a primary path next hop. The method improves RLFA computation efficiency for a Q-Space list of nodes in a Q-space for an endpoint node by reducing calculations of the loop free condition for a path from a source node to a destination node via a tunnel between the source node and the endpoint node. The method includes adding a neighbor node to a poison list where the candidate node is in the poison list and the neighbor node is not in the candidate list, the poison list indicating that a node is not a candidate for Q-Space, and determining the Q-Space list by removing nodes from poison list from the plurality of nodes.

Abstract: A network element that acts as a hub in a hub and spoke topology is configured to limit the amount of topology and reachability information that is advertised to a set of one or more remote network elements that act as one or more spokes in the hub and spoke topology in a same routing area. The network element generates a set of one or two link state advertisements (LSAs) to advertise over an interface that connects at least one of the set of remote network elements to the network element, wherein the set of LSAs includes information that describes a connection to the set of remote network elements and one or more aggregate routes. The network element advertises, during a database exchange process with the one of the set of remote network elements, the set of LSAs to the one of the set of remote network elements.

Abstract: A method is implemented by a network element to improve efficiency of loop free alternative (LFA) path computation by caching data from a shortest path first calculation for use in the LFA path calculation. The shortest path first calculation determines a shortest path from a source vertex to each vertex in a network topology graph representing the network in which the network element operates, where an endpoint for each shortest path is the shortest path vertex, and where each shortest path determined by the shortest path first calculation is stored.

Abstract: A method is implemented by a network device to improve efficiency of computing a node-protecting remote loop-free alternate (LFA) in a network topology graph. The method computes a reverse shortest path first (SPF) algorithm rooted at the primary next hop node, where the reverse SPF algorithm rooted at the primary next hop maintains a reverse path of a shortest path computed by the reverse SPF algorithm rooted at the primary next hop node. The method selects a node that is in both the source node's node-protecting extended P-space that protects the primary next hop node and the primary next hop node's link-protecting Q-space that protects the S-E link.

Abstract: A method is implemented by a network device to improve efficiency of computing a node-protecting remote loop-free alternate (LFA) in a network topology graph. The method computes a reverse shortest path first (SPF) algorithm rooted at the primary next hop node, where the reverse SPF algorithm rooted at the primary next hop maintains a reverse path of a shortest path computed by the reverse SPF algorithm rooted at the primary next hop node. The method selects a node that is in both the source node's node-protecting extended P-space that protects the primary next hop node and the primary next hop node's link-protecting Q-space that protects the S-E link.

Abstract: An automated key transition method is executed by a node in a network. The network includes a set of nodes utilizing a current key identifier. A key identifier specifies an authentication protocol and an authentication key for use in the authentication of intermediate-system to intermediate-system (IS-IS) protocol data units. The method includes a set of steps including receiving a message at the node, where, the message includes a most recent key identifier to replace the current key identifier, verifying whether all reachable nodes in the set of nodes have advertised the most recent key identifier, continuing authentication using the current key identifier until all reachable nodes in the set of nodes have been verified to advertise the most recent key identifier, and switching authentication at the node to use the most recent key identifier upon verification that all reachable nodes in the set of nodes have advertised the most recent key identifier.

Abstract: A technique dynamically configures and verifies routing information of broadcast networks using link state protocols in a computer network. According to the novel technique, a router within the broadcast network receives a link state protocol routing information advertisement from an advertising router, e.g., a designated router or other adjacent neighbor. The router learns of a next-hop router (“next-hop”) to reach a particular destination from the advertisement, and determines whether the next-hop is located within the same broadcast network (e.g., subnet) as the designated router. If so, the router further determines whether the next-hop is directly addressable (i.e., reachable), such as, e.g., by checking for link adjacencies to the next-hop or by sending request/reply messages (e.g., echo messages or “ping” messages) to the next-hop. In the event the next-hop for the destination is not directly addressable by the router (e.g.

Abstract: A network element of a communications network includes a fresh route queue, a stale route queue, a Routing Information Base (RIB), a network interface, and a routing protocol module. The network interface receives link state information from other network elements. The routing protocol module determines a plurality of routes from the link state information. The routing protocol module identifies among the plurality of routes a subset of routes that are present in the stale route queue, adds the subset of routes to the fresh route queue, and deletes the subset of routes from the stale route queue. The routing protocol module then remove routes in the RIB that correspond to any routes remaining in the stale route queue, and moves the routes from the fresh route queue to the stale route queue. Related methods for managing routes in a RIB of a network element are disclosed.

Abstract: A method is implemented by a network element to improve efficiency of loop free alternative (LFA) path computation by caching data from a shortest path first calculation for use in the LFA path calculation. The shortest path first calculation determines a shortest path from a source vertex to each vertex in a network topology graph representing the network in which the network element operates, where an endpoint for each shortest path is the shortest path vertex, and where each shortest path determined by the shortest path first calculation is stored.

Abstract: An automated key transition method is executed by a node in a network. The network includes a set of nodes utilizing a current key identifier provided by a group key management server or provisioned manually. A key identifier specifies an authentication protocol and an authentication key for use in the authentication of intermediate-system to intermediate-system (IS-IS) protocol data units. The method includes receiving a message from the group key management server that includes a most recent key field to replace the current key identifier, advertising the most recent key identifier to all reachable nodes, verifying whether all reachable nodes have advertised the most recent key identifier, continuing authentication using the current key identifier until all reachable nodes have been verified to advertise the most recent key identifier, and switching authentication to use the most recent key identifier upon verification that all reachable nodes have advertised the most recent key identifier.

Abstract: A network element is configured to reduce the synchronization costs for implementing Open Shortest Path First (OSPF) Nonstop routing (NSR). The reduced synchronization costs are achieved by reducing the number of acknowledgement messages that are needed to be sent though reliable inter-process communication (IPC) between the active OSPF instance and the standby OSPF instance. The number of acknowledgement messages is reduced by tracking the link state advertisements (LSAs) that have been sent by the active OSPF instance to the standby OSPF instance and by the standby OSPF replying with an acknowledgement of only the last LSA in a group of LSAs received from the active OSPF instance, where the group can have a variety of boundaries such as a group of LSAs in an IPC message. This avoids having a significant number of acknowledgement messages sent through the IPC.

Abstract: Open Shortest Path First (OSPF) Non-stop Routing (NSR) with frozen standby LSDB is described. A network element includes a first OSPF instance initially acting as an active OSPF instance and a second OSPF instance initially acting as a standby OSPF instance. The second OSPF instance receives LSAs from the first OSPF instance and installs the LSAs in its LSDB. The LSAs in the LSDB are only aged by the active OSPF instance. If and when the second OSPF instance becomes the active OSPF instance, the second OSPF instance then ages the LSAs in the LSDB and processes each of the LSAs according to the aging of that LSA, where processing includes one of purging that LSA and refreshing that LSA.

Abstract: A method is implemented by a network element for determining a next hop of a backup path for a fast reroute process to be utilized in response to a network event invalidating a primary path to a destination node. The method reduces computational requirements of the network element by reducing a number of paths to be evaluated without affecting selection of the backup path. The method selects a neighbor node P of a source node S to calculate a shortest path tree (SPT) for P for use in identifying backup paths for S. The SPT is calculated for P, pruning paths from the SPT that traverse S or that fail an LFA condition. P is selected for the next hop of the backup path for a destination node X where the SPT of P provides an LFA path from S to the destination node X.

Abstract: A network element is configured for synchronizing dynamic OSPF data between an active OSPF instance and a backup OSPF instance. Upon an OSPF data synchronization event, the active OSPF instance synchronizes dynamic OSPF data with the backup OSPF instance. Upon receiving the dynamic OSPF data, the backup OSPF instance determines whether the requisite data structures exist. If the data structures do not exist, the backup OSPF instance returns a NACK to the active OSPF instance and clears its dynamic OSPF data. Responsive to receiving the NACK, the active OSPF instance resynchronizes its dynamic OSPF data with the backup OSPF instance.

Abstract: OSPF NSR with link derivation synchronization is described. When a network element having an active OSPF instance and a standby OSPF instance attempts to create a FULL adjacency with a neighbor network element using a neighbor data structure of the active OSPF instance, and if and when a switch causes the second OSPF instance to act as the active OSPF instance, neighbor information is retrieved from the LSAs of the standby OSPF instance and a link is derived between the network element and the neighbor network element based on the retrieved neighbor information. In one embodiment, the standby OSPF instance retrieves virtual neighbor information from its LSAs and derives a virtual link between the network element and the neighbor network element based on the retrieved virtual neighbor information without having to synchronize the neighbor information between the active and standby OSPF instance.

Abstract: Methods and apparatus for a network element to handle LSID collisions to prevent different LSAs associated with different routes from sharing the same LSID. According to one embodiment, responsive to determining that a tentative LSID that is generated for a first route that is being added collides with an LSID that is assigned to an LSA for a second route, and that one of the first and second routes is a host route, the host route is suppressed. If the first route is the host route, suppressing includes not originating an LSA for the first route. If the second route is the host route, suppressing includes purging the LSA for the second route and not originating an LSA for the second route. Although the host route is suppressed, network reachability of the range subsuming the host route is provided through the route that is not the host route.

Abstract: A network element is configured for open shortest path first (OSPF) non-stop routing (NSR) with reliable flooding. An active OSPF instance determines to flood a link-state advertisement (LSA). The LSA is synchronized with a backup OSPF instance including storing the LSA with a status that indicates that flooding is pending. The active OSPF instance attempts to reliably flood the LSA to a set of adjacent network elements of the flooding scope of the LSA. If flooding of the LSA completes, the active OSPF instance causes the backup OSPF instance to alter the status of the LSA to indicate that flooding is complete. If the backup OSPF instance becomes the currently active OSPF instance prior to the flooding of the LSA completing, then the new active OSPF instance attempts to reliably flood the LSA.

Abstract: A network element that acts as a hub in a hub and spoke topology is configured to limit the amount of topology and reachability information that is advertised to a set of one or more remote network elements that act as one or more spokes in the hub and spoke topology in a same routing area. The network element generates a set of one or two link state advertisements (LSAs) to advertise over an interface that connects at least one of the set of remote network elements to the network element, wherein the set of LSAs includes information that describes a connection to the set of remote network elements and one or more aggregate routes. The network element advertises, during a database exchange process with the one of the set of remote network elements, the set of LSAs to the one of the set of remote network elements.

Abstract: In one embodiment, a first router determines whether a network coupling the first router to one or more second routers is transit-only, wherein transit-only indicates connecting only routers to provide for transmission of data from router to router. When the network is transit-only, the first router generates an Open Shortest Path First (OSPF) Link State Advertisement (LSA) that includes an address for the network and a designated network mask. The designated network mast operates as a transit-only identification that indicates the address should not be installed in a Routing Information Base (RIB) upon receipt of the OSPF LSA at the one or more second routers. When the network is not transit-only, the first router generates an OSPF LSA that includes the address for the network but does not include the designated network mask, to permit installation of the address in a RIB upon receipt of the OSPF LSA at the one or more second routers.