OSPF non-stop routing frozen standby

摘要

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.

主权项

1. A method in a network element for open shortest path first (OSPF) non-stop routing, wherein the 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 method comprising the steps of:
receiving, at the second OSPF instance, a plurality of link-state advertisements (LSAs) from the first OSPF instance; the second OSPF instance installing the LSAs in its link-state database (LSDB), wherein the LSAs in the LSDB are not aged by the second OSPF instance when acting as the standby OSPF instance; and responsive to the second OSPF instance becoming the active OSPF instance, the second OSPF instance performing the following steps:
aging the LSAs in the LSDB, andprocessing each of the LSAs according to the aging of that LSA, wherein processing includes one of purging that LSA and refreshing that LSA,wherein aging the LSAs include listing the LSAs in a timer structure having a plurality of buckets that are processed sequentially according to an aging clock,wherein each LSA is listed in one of the plurality of buckets according to an age of that LSA,wherein the aging clock is not running when the second OSPF instance is acting as the standby OSPF instance, andwherein the second OSPF instance, when operating as the standby OSPF instance, lists each LSA received from the first OSPF instance in one of the buckets that will be first processed when the second OSPF instance becomes the active OSPF instance.