OSPF non-stop routing with reliable flooding
First Claim
1. A method in a network element for open shortest path first (OSPF) non-stop routing with reliable flooding, the method comprising the steps of:
- responsive to a first OSPF instance of the network element that is currently acting as an active OSPF instance determining to flood a link-state advertisement (LSA), performing the following steps;
synchronizing the LSA with a second OSPF instance of the network element currently acting as a backup OSPF instance, wherein the step of synchronizing includes storing by the second OSPF instance the LSA with a status that indicates that flooding is pending;
attempting to reliably flood by the first OSPF instance the LSA to a set of one or more adjacent network elements of a flooding scope of the LSA, the step of attempting includes;
transmitting the LSA to each of the set of adjacent network elements in the flooding scope of the LSA with an exception of one adjacent network element if the LSA was received from that adjacent network element,including the LSA on a plurality of retransmission lists for the plurality of adjacent network elements that the LSA was transmitted to, andmaintaining the plurality of retransmission lists on the first OSPF instance, wherein the plurality of retransmission lists are not synchronized with the second OSPF instance, wherein the step of maintaining includes removing the LSA from a retransmission list for a network element responsive to receiving an acknowledgement of receipt of that LSA from that network element,if flooding of the LSA is complete, then the first OSPF instance causing the second OSPF instance to alter the status of the LSA to indicate that flooding is complete, wherein the flooding of the LSA is complete when the LSA is not indicated on any of the plurality of retransmission lists; and
if the second OSPF instance has become the currently active OSPF instance prior to the flooding of the LSA completing, then the second OSPF instance attempting to reliably flood the LSA to all of the set of adjacent network elements of the flooding scope of the LSA.
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Accused Products
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.
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Citations
18 Claims
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1. A method in a network element for open shortest path first (OSPF) non-stop routing with reliable flooding, the method comprising the steps of:
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responsive to a first OSPF instance of the network element that is currently acting as an active OSPF instance determining to flood a link-state advertisement (LSA), performing the following steps; synchronizing the LSA with a second OSPF instance of the network element currently acting as a backup OSPF instance, wherein the step of synchronizing includes storing by the second OSPF instance the LSA with a status that indicates that flooding is pending; attempting to reliably flood by the first OSPF instance the LSA to a set of one or more adjacent network elements of a flooding scope of the LSA, the step of attempting includes; transmitting the LSA to each of the set of adjacent network elements in the flooding scope of the LSA with an exception of one adjacent network element if the LSA was received from that adjacent network element, including the LSA on a plurality of retransmission lists for the plurality of adjacent network elements that the LSA was transmitted to, and maintaining the plurality of retransmission lists on the first OSPF instance, wherein the plurality of retransmission lists are not synchronized with the second OSPF instance, wherein the step of maintaining includes removing the LSA from a retransmission list for a network element responsive to receiving an acknowledgement of receipt of that LSA from that network element, if flooding of the LSA is complete, then the first OSPF instance causing the second OSPF instance to alter the status of the LSA to indicate that flooding is complete, wherein the flooding of the LSA is complete when the LSA is not indicated on any of the plurality of retransmission lists; and if the second OSPF instance has become the currently active OSPF instance prior to the flooding of the LSA completing, then the second OSPF instance attempting to reliably flood the LSA to all of the set of adjacent network elements of the flooding scope of the LSA. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A network element for open shortest path first (OSPF) non-stop routing with reliable flooding, comprising:
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a first OSPF instance, configured to initially act as an active OSPF instance, and having a first reliable flooding module; a second OSPF instance, configured to initially act as a standby OSPF instance, having a link state database (LSDB), a second reliable flooding module, and a flood pending list; wherein the first reliable flooding module is configured to; cause link-state advertisements (LSAs) that it has determined to flood to be stored in the link state database and include each of those LSAs to be flooded on the flood pending list until flooding of that LSA is complete; reliably flood the LSAs stored on the flood pending list to one or more adjacent network elements, wherein reliable flooding of an LSA is complete when an acknowledgement is received from each of the set of adjacent network elements; upon reliable flooding of an LSA being complete, cause that LSA to be removed from the flood pending list of the second OSPF instance; and wherein the second reliable flooding module is configured to; after the second OSPF instance becomes the active OSPF instance, flood all LSAs included on the flood pending list to one or more adjacent network elements. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method in a network element for open shortest path first (OSPF) non-stop routing with reliable flooding, the network element including a first OSPF instance that initially is acting as an active OSPF instance and a second OSPF instance that initially is acting as a backup OSPF instance, the method comprising the steps of:
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the first OSPF instance reliably flooding LSAs, wherein for each LSA to be flooded, the first OSPF instance synchronizes that LSA with the second OSPF instance with a status of flood pending; responsive to reliable flooding of an LSA being complete, the first OSPF instance causing the second OSPF instance to alter the status of that LSA to indicate that flooding is complete including the first OSPF instance sending a message notifying the second OSPF instance that flooding is complete; and responsive to the second OSPF instance becoming the currently active OSPF instance, the second OSPF instance reliably flooding those LSAs that have a status of flood pending. - View Dependent Claims (15, 16, 17, 18)
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Specification