Abstract: In one embodiment, a first router determines whether an interface coupling the first router to one or more second routers is transit-only. When the interface is transit-only, the first router generates an Open Shortest Path First (OSPF) Link State Advertisement (LSA) that includes an address for the interface and a designated network mask. The designated network mask 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 interface 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.

Abstract: Techniques are provided for generating efficient flooding tree paths in a network. At a node device in a network, a unicast message is sent to a plurality of node devices in the network. The node device obtains an identifier associated with each of the node devices in the network. The identifier contains information indicating node connectivity for each of the node devices. A selected node device is then identified. The selected node device is one of the node devices in the network that has a lowest identifier value indicating a lowest number of connected node devices to the selected node device in the network. The selected node device is classified as a root flooding tree node device. A flooding tree is generated by performing a shortest path first operation from the selected node device to the plurality of node devices in the network.

Abstract: In one embodiment, a first router determines whether an interface coupling the first router to one or more second routers is transit-only. When the interface is transit-only, the first router generates an Open Shortest Path First (OSPF) Link State Advertisement (LSA) that includes an address for the interface and a designated network mask. The designated network mask 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 interface 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.

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.

Abstract: Techniques are provided for generating efficient flooding tree paths in a network. At a node device in a network, a unicast message is sent to a plurality of node devices in the network. The node device obtains an identifier associated with each of the node devices in the network. The identifier contains information indicating node connectivity for each of the node devices. A selected node device is then identified. The selected node device is one of the node devices in the network that has a lowest identifier value indicating a lowest number of connected node devices to the selected node device in the network. The selected node device is classified as a root flooding tree node device. A flooding tree is generated by performing a shortest path first operation from the selected node device to the plurality of node devices in the network.

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.

Abstract: A novel technique is provided for preventing routing loops by disseminating Border Gateway Protocol (BGP) attribute information in an Open Shortest Path First (OSPF) configured network. Specifically, a new OSPF sub-type-length-value (TLV) is introduced for transporting a conventional BGP autonomous system (AS) path attribute through the OSPF-configured network. Like the BGP AS-path attribute, the new OSPF AS-path sub-TLV is configured to store a set of AS numbers corresponding to the AS path of one or more advertised routes. Thus, when a network device receives an OSPF link-state advertisement (LSA) containing the novel AS-path sub-TLV, the network device determines whether it resides in an autonomous system whose AS number is stored in the sub-TLV. If so, the network device does not install the LSA's advertised routes in its link-state database since the routes, if installed, could result in routing loops.

Abstract: In one embodiment, a Link State Advertisement (LSA) is received from a first router in a network at a second router in the network. The LSA advertises an address of an interface of the first router. The second router determines whether the LSA includes a transit-only identification that indicates the interface of the first router is a transit-only interface. If the LSA does not include a transit-only identification, the second router installs the advertised address of the interface of the first router in a Router Information Base (RIB) of the second router. If the LSA does include a transit-only identification, the second router declines to install the advertised address of the interface of the first router in the RIB of the second router.

Abstract: A method and apparatus for routing data in a network is disclosed. A spoke router signals its intention to act as spoke in a new bit in Hello and database descriptor packets. A router acting as hub acknowledges the spoke request. Once the spoke router receives the hub's acknowledgement, it installs a default route to the hub router. Flooding is suppressed from hub to spoke. Instead of flooding, the hub router sends empty database descriptor packets so that no request is sent from spoke routers and any further change in the topology is not sent to spoke routers. This minimizes the flooding in this environment.

Abstract: The present invention elects an area border router from a plurality of potential area border routers by determining a full set of all areas attached to a router. A determination is made as to a full set of area pairs from the determined full set of areas. Routers are identified in a first area of the determined full set of areas that are reachable through an intra-area route in the first area, and routers are identified in a second area of the determined full set of areas that are reachable through an intra-area route in the second area. If there is a router that is unreachable through either an intra-area route in the first area or an intra-area route in the second area, then declare the first router to be an area border router, else new first and second areas are selected.

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: In one embodiment, a Link State Advertisement (LSA) is received from a first router in a network at a second router in the network. The LSA advertises an address of an interface of the first router. The second router determines whether the LSA includes a transit-only identification that indicates the interface of the first router is a transit-only interface. If the LSA does not include a transit-only identification, the second router installs the advertised address of the interface of the first router in a Router Information Base (RIB) of the second router. If the LSA does include a transit-only identification, the second router declines to install the advertised address of the interface of the first router in the RIB of the second router.

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: A system for hiding transit-only interfaces in a network. When a routing system is advertising a transit-only interface, the advertisement is marked to indicate the address is a transit-only interface. A routing system receives the advertisement and detects the identifier of the transit-only interface and does not store the address in the Router Information Base of the routing system.

Abstract: Techniques for detecting loops in routes that cross route information boundaries include receiving a control message at a first edge node on one side of the boundary that is connected to a different second edge node on another side of the boundary. The control message indicates a particular network address of a particular node that is reachable from the first edge node. Distinguisher data is determined that indicates if a node in the first collection can reach the first edge node without leaving the first collection. An advertising message is sent from the first edge node to the second edge node that includes route data that indicates the particular network address and the distinguisher data. Based on the distinguisher data, a testing edge node in the first collection can determine whether there is a loop comprising both an internal path and an external path to the first edge node.

Abstract: A technique maintains Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network. According to the novel technique, a first CE generates a BGP advertisement to advertise one or more VPN routes of its customer network, the BGP advertisement having one or more transitive IGP attributes for the advertised routes. The first CE sends the BGP advertisement to a first PE, which then propagates the BGP advertisement among devices of a provider network maintaining the transitive IGP attributes. A second PE sends the BGP advertisement to a second CE, along with the transitive IGP attributes. Upon receiving the BGP advertisement, the second CE converts the BGP advertisement and transitive IGP attributes into corresponding IGP advertisements.

Abstract: In one embodiment, a method includes receiving a neighbor discovery message and a border routing message through an interface at a particular router. The interface communicates with a border network segment between first nodes routing with IPv6 using a first routing protocol and different second nodes routing using a different routing protocol. The messages are received from an alien router. The border routing message includes foreign routing data that indicates a route among the second nodes. If the alien router's interface on the border segment does not have a global IPv6 address, then a fictive IPv6 address is generated, which includes a global prefix of an IPv6 address for the particular router and an interface identifier associated with the alien router. The fictive IPv6 address and the foreign routing data are inserted into a domain scope external advertisement message that is sent to the first nodes.

Abstract: A method of supporting a unidirectional link from a first router to a second router, the first and second routers existing in an area of a communication network, the method comprising: the second router receiving a hello packet from the first router; the second router determining that its topology information for the communication network is incomplete; the second router encapsulating an open shortest path first (OSPF) packet into an Opaque link state advertisement (LSA); and the second router flooding the Opaque LSA over the area.

Abstract: The present invention provides a method of determining whether database located on a first router is synchronized with the database located on a second router by performing a hash function on the values contained in a link state database to derive a SHA-1 digest value. In an embodiment, the digest value is based on LSA type. The digest value is exchanged initially during a database description packet swap between the first router and second router. If the digest values are the same, the databases are already synchronized. The routers thus skip the database description packet exchange of LSAs in the database and go directly to FULL state, indicating full synchronization between databases on the first and second router and announcing adjacency to each other. If the digest differs, normal database description packet exchange is performed as specified in OSPF.

Abstract: In one embodiment, a method includes receiving a neighbor discovery message and a border routing message through an interface at a particular router. The interface communicates with a border network segment between first nodes routing with IPv6 using a first routing protocol and different second nodes routing using a different routing protocol. The messages are received from an alien router. The border routing message includes foreign routing data that indicates a route among the second nodes. If the alien router's interface on the border segment does not have a global IPv6 address, then a fictive IPv6 address is generated, which includes a global prefix of an IPv6 address for the particular router and an interface identifier associated with the alien router. The fictive IPv6 address and the foreign routing data are inserted into a domain scope external advertisement message that is sent to the first nodes.