Detection of network topology changes affecting trail routing consistency

• US 6,564,258 B1
• Filed: 11/16/1998
• Issued: 05/13/2003
• Est. Priority Date: 09/30/1998
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Uniacke, Mark
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): NGUYEN, THU HA T
• Application Number:
  US09/193,094
• Time in Patent Office: 1,639 Days
• Field of Search: 709/201-203, 709/220-224, 710/220, 707/10, 370/14
• US Class Current: 709/223
• CPC Class Codes: H04L 43/0811 by checking connectivity
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

There is disclosed a method and apparatus for detection of client trails which may become unsupported due to reconfiguration of node elements within a network at a server layer, and a rerouting apparatus and method for proposing a set of alternative routes to support client trails during reconfiguration of a network at a physical layer. Data describing each trail, connection, node, link and other physical resource is maintained in a managed object database on a network controller. A trail detection algorithm investigates trail termination points corresponding to proposed deleted or created trails to see if those termination points support client trails at higher layers. If supported client trails are detected at higher layers, a routing algorithm is applied to find a set of alternative routes over which the client layer trails may be rerouted during network configuration at the physical or server layer.

Claims

1. In a communications network comprising a plurality of resources arranged in a plurality of layers wherein resources at a client layer are dependent upon resources at a server layer, the network including means for maintaining an object database describing a plurality of resources of said communications network, said object database comprising a plurality of instances representing physical and logical resources, the network further including means for modifying individual ones of said plurality of instances when a said resource is re-configured by setting a state of a said instance,

a method of determining an alternative network connectivity for a client layer resource of said network affected by a network topology change at a server layer of said communications network, said method comprising the steps of:

determining if the client layer resource is affected by a network topology change affecting a server layer resource; and

in the event that said client layer resource is affected by said change,

determining an alternative network connectivity for said at least one client layer resource affected by said change.

2. The method as claimed in claim 1, wherein said plurality of instances include instances selected from the set:

an instance representing a node entity;

an instance representing an endpoint;

an instance representing a trail;

an instance representing a trail termination point;

an instance representing a connection;

an instance representing a connection termination point;

an instance representing a link connection;

an instance representing a port;

an instance representing a sub network connection;

an instance representing a link;

an instance representing a link termination point.

3. The method as claimed in claim 1, wherein a one of said plurality of instances represents a trail, the method further comprising the step of receiving a signal for deletion of said trail, wherein in response to said received signal, said object database is interrogated to determine whether said trail subject of said delete signal supports a client trail.

4. The method as claimed in claim 1, wherein a one of said plurality of instances represents a trail, the method further comprising the steps of:

receiving a signal for deletion of said trail;

on receipt of said delete signal determining whether said trail subject of said signal is supporting a client trail; and

if said trail subject of said delete signal is supporting a client trail, setting said state of said trail to a data signify said trail is supporting at least one client trail by setting a data in said object database.

5. The method as claimed in claim 4, further comprising the step of setting data describing a said client trail to a state signifying deletion of said trail is inconsistent with supporting said client trail.

6. A method as claimed in claim 1, further comprising reconfiguring said server layer resource by setting a said state of a said instance of said server layer resource to indicate said change has said effect on said client layer resource.

7. A method as claimed in claim 1, further comprising reconfiguring said server layer resource by setting a said state of a said instance of said server layer resource to indicate said change has said effect on said client layer resource, and reconfiguring said client layer resource by setting a said state of a said instance of said client layer resource to indicate said change has said effect on said client layer resource.

8. A method as claimed in claim 1, further comprising the steps of reconfiguring said client layer resource by setting a state of a said instance of said client layer resource to indicate said alternative network connectivity.

9. A method as claimed in claim 1, wherein said alternative network connectivity includes at least one server layer resource differing from the server layer resource initially affected by the change to the network connectivity.

10. A method of managing a communications network comprising a plurality of network resources, said method comprising the steps of:

representing each of a plurality of said network resources by managed object data in a managed object database;

inputting signals describing deletion of a said resource at a server layer;

interrogating said set of managed object data to find a set of client resources dependant on said server resource, and setting a managed object data for said resource at said server layer to indicate said server layer resource supports said set of client resources, characterised in that the method further includes the steps of;

determining if at least one alternative server layer resource is able to support said set of client resources.

11. The method as claimed in claim 10 wherein said managed object data describing said resources comprises connection rule data describing a plurality of rules for connecting said plurality of resources.

12. The method as claimed in claim 10, wherein said plurality of network resources include resources selected from the set:

transmission entities;

physical resources;

logical resources.

13. The method as claimed in claim 10, wherein said managed object data describes at least one element selected from the following set:

trail termination point;

connection termination point;

connection;

link;

link connection;

physical port;

logical port;

sub network connection;

server trail;

client trail;

server link;

client link.

14. A method as claimed in claim 10, further comprising the step of setting managed object data for said client resources to indicate that alternative server layer resources are able to support said set of client resources.

15. A method as claimed in claim 10, further comprising the steps of:

setting managed object data for said client resources to indicate that alternative server layer resources are able to support said set of client resources; and

setting a managed object data for said resource at said server layer to indicate said server layer resource is an alternative source of support for said set of client resources.

16. A network management apparatus for a communications system comprising a plurality of nodes, said network management apparatus comprising:

at least one data processor;

at least one data storage means;

wherein said processor and said data storage means are configured as a managed object database comprising a plurality of managed object data representing a plurality of resources of said communications network; and

a said processor operates in accordance with an algorithm to detect a topology change to a configuration of said plurality of resources, wherein said managed object data includes data describing if at least one alternative resource in a server layer of said communications system is able to support a resource in a client layer of said communications system affected by said change.

17. The apparatus as claimed in claim 16, wherein a said processor operates in accordance with an algorithm to find a plurality of routes across said network in response to a detected change of configuration of said plurality of resources.

18. The apparatus as claimed in claim 16, wherein a said processor operating in accordance with said detection algorithm operates to read a plurality of states of said managed objects of said managed object database.

19. The apparatus as claimed in claim 16, wherein a said topology change comprises a physical topology change.

20. The apparatus as claimed in claim 16, wherein a said topology change comprises a logical topology change.

21. The apparatus as claimed in claim 16, wherein a plurality of topological changes are made at the server layer of said network, the managed object data further comprising data determining which of a set of client layer trails are affected.

22. In a layered synchronous network comprising a plurality of resources arranged in a plurality of layers, wherein resources at a first layer of the layered synchronous network are dependent on resources at another layer of the layered synchronous network, and wherein a trail in said first layer of the network is supported by a route in a physical layer of said layered synchronous network, wherein a topological change to the physical layer affects the route such that the trail becomes unsupported, a computerised method of re-routing a client trail supported by a server trail comprising the steps of:

detecting the effect of said topological change to the physical network on the client trail;

determining if a second route can be implemented to support said client trail;

determining if a characteristic of said client trail requires modification to implement said second route.

23. A method as claimed in claim 22, wherein said characteristic is an adaptation rule for said trail.

24. A method as claimed in claim 22, wherein said topological change is the disconnection of a physical link in the network.

25. A method as claimed in claim 22, wherein said first layer is a logical layer.

26. A method as claimed in claim 22, wherein said first layer is a logical layer taken from the group consisting of:

the optical section layer;

the regenerator section layer;

the multiplex section layer;

higher order layer; and

lower order layer.

27. A method as claimed in claim 22, wherein said step of determining if a characteristic of said client trail requires modification to implement said second route comprises:

identifying data describing at least one endpoint of said client trail;

determining from said endpoint data whether said client trail requires modification.

28. A method as claimed in claim 27, wherein said step of detecting the effect of said topological change to the physical network on the client trail further comprises determining if said server trail is in a state suitable for deletion.

29. A method as claimed in claim 27, wherein said step of determining if a second route can be implemented to support said client trail comprises:

assigning a cost data to each of a plurality of network resources; and

determining an optimum route on the basis of said cost data.

30. A method as claimed in claim 29, wherein a said cost data is assigned on the basis of an availability of a said network resource.

31. A method as claimed in claim 29, wherein a said cost data is assigned on the basis of a least number of hops between node entities.