OSPF non-stop routing frozen standby

• US 8,958,430 B2
• Filed: 01/12/2012
• Issued: 02/17/2015
• Est. Priority Date: 09/29/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Chen, Ing-Wher, Lu, Wenhu, Lindem, Alfred C. III
• Primary Examiner(s): HALIYUR, VENKATESH N
• Application Number:
  US13/349,530
• Publication Number:
  US 20130083802A1
• Time in Patent Office: 1,132 Days
• Field of Search: 370208-509, 709223-242
• US Class Current: 370/401
• CPC Class Codes: H04L 45/023 Delayed use of routing table updates
• CPC Class Codes: H04L 45/12 Shortest path evaluation
• CPC Class Codes: H04L 45/123 Evaluation of link metrics techniques for monitoring network metrics H04L43/08
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/58 Association of routers
• CPC Class Codes: H04L 45/60 Router architectures

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.

Claims

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, and

processing 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, and

wherein 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.

2. The method of claim 1, wherein the second OSPF instance, when it becomes the active OSPF instance, performs the following:

moving the received LSAs into appropriate buckets to be processed at an appropriate time.

3. The method of claim 2, wherein the second OSPF instance, responsive to it becoming the active OSPF instance, processes those LSAs listed in the timer structure that are due or overdue to be processed in a first timing window.

4. An apparatus, comprising:

a network element supporting open shortest path first (OSPF) non-stop routing with a first OSPF instance that is configured to initially act as an active OSPF instance and a second OSPF instance that is configured to initially act as a standby OSPF instance, the network element including one or more processors configured to implement;

the first OSPF instance including a first aging module, wherein the first OSPF instance is configured to install link-state advertisements (LSAs) in a first link-state database (LSDB) associated with the first OSPF instance and synchronize the LSAs with the second OSPF instance, and wherein the first aging module is configured to, while the first OSPF instance is acting as the active OSPF instance, age LSAs in the first LSDB and process each one of those LSAs according to the aging including one of purging that LSA and refreshing that LSA; and

the second OSPF instance coupled with the first OSPF instance and including a second aging module, wherein the second OSPF instance is configured to install those LSAs synchronized from the first OSPF instance in a second LSDB associated with the second OSPF instance, and wherein the second aging module is configured to process LSA aging events for the LSAs in the second LSDB only when the second OSPF instance becomes the active OSPF instance.

5. The network element of claim 4, wherein the first OSPF instance further includes:

a first timer structure having a first plurality of buckets, wherein the first aging module is configured to list each LSA it synchronizes with the second OSPF instance in the first timer structure in an appropriate one of the first plurality of buckets based on a time when that LSA is to be refreshed or purged; and

a first aging clock configured to cause the first aging module to process the LSAs listed in an LSA timer structure.

6. The network element of claim 5, wherein the second OSPF instance further comprises:

a second timer structure having a second plurality of buckets, wherein the second aging module is configured to, when the second OSPF instance is acting as the standby OSPF instance, list each LSA it receives from the first OSPF instance in a same one of the second plurality of buckets; and

a second aging clock configured to be inactive when the second OSPF instance is acting as the standby OSPF instance such that the LSAs listed in the second timer structure will not be processed by the standby OSPF instance; and

wherein the second aging module is configured to, when the second OSPF instance is acting as the standby OSPF instance, activate the second aging clock to cause the second aging module to process the LSA aging events.

7. The network element of claim 5, wherein the second OSPF instance is further configured to, upon becoming the active OSPF instance, distribute each LSA that is listed in a second timer structure and is not due or overdue to be processed to an appropriate one of a second plurality of buckets of the second timer structure according to the age of that particular LSA.

8. The network element of claim 7, wherein the second OSPF instance, responsive to it becoming the active OSPF instance, processes those LSAs listed in the second timer structure that are due or overdue to be processed in a first timing window.

9. A method in a network element for open shortest path first (OSPF) non-stop routing comprising:

receiving, at a first OSPF instance that is currently acting as a standby OSPF instance, a link-state advertisement (LSA) from a second OSPF instance that is currently acting as an active OSPF instance;

the first OSPF instance storing that LSA in a link-state database (LSDB), wherein that LSA is not aged by the first OSPF instance until and unless the first OSPF instance becomes the active OSPF instance;

responsive to the first OSPF instance becoming the active OSPF instance, the first OSPF instance performing the following;

aging that LSA, and

processing that LSA according to the age of that LSA, wherein the step of processing includes one of purging that LSA and refreshing that LSA,

wherein the step of aging the LSA includes listing that LSA in one of a plurality of buckets of a timer structure that are processed sequentially according to an aging clock, wherein the LSA is listed in that one bucket according to the age of the LSA,

wherein the aging clock of the first OSPF instance is not running when the first OSPF instance is acting as the standby OSPF instance, and

wherein the first OSPF instance, when operating as the standby OSPF instance, lists the LSA received from the second OSPF instance in one of a plurality of buckets of a timer structure that will be first processed when the first OSPF instance becomes the active OSPF instance.

10. The method of claim 9, wherein the first OSPF instance, when it becomes the active OSPF instance, performs the following:

moving the received LSA into an appropriate one of the buckets to be processed at an appropriate time.