Resolving conflicting topology information

• US 5,568,605 A
• Filed: 01/13/1994
• Issued: 10/22/1996
• Est. Priority Date: 01/13/1994
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Zeiger, John H., Graham, John S. Jr., Clouston, Robert D.
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): Courtenay, III, St. John
• Application Number:
  US08/180,725
• Time in Patent Office: 1,013 Days
• Field of Search: 395/200, 395/180
• US Class Current: 714/4.1
• CPC Class Codes: H04L 41/046 comprising network management agents or mobile agents therefor
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies

Abstract

A topology manager external to a communications network manages the network and in particular resolves conflicting topology information about the network by dividing the management of the topology data base into two operations--a collection instance and a resolution layer. A collection instance collects all information that its agent node has about the topology of the network. This topology information is processed by the collection instance to determine for each resource in the network whether the resource is new, reachable or has experienced a reachability change. The resolution layer receives the topology resource information from each collection instance. When a resource is indicated as reachable by a collection instance, that resource is placed on a Reach list as an entry from that collection instance. If the collection instance indicates the resource from that collection instance is no longer reachable, the resolution layer will remove that resource entry from the Reach list, and look for another Best Reach entry for the resource. If the network fragments and nodes go down and come back up, the resolution layer can resolve conflicts in resource information from separate collection instances to select the most current information for a resource.

Claims

1. In a communication network having a plurality of network resources as nodes or transmission groups between nodes, topology manager apparatus that has an agent in at least some of the nodes, said topology manager apparatus comprising:

a plurality of collecting means, each collecting means for collecting topology information from an associated agent, said topology information indicating the topology of the network as viewed by the associated agent;

each of said plurality of collecting means providing resource information about each network resource as viewed by the associated agent, said resource information indicating the reliability, time and sequence of the resource information;

means within each of said plurality of collecting means for analyzing the connectivity of each network resource from the topology information that is provided by the associated agent, for providing status information about each network resource that is included in the topology information that is provided by the associated agent, and for providing reachability information indicating whether a network resource is reachable from the associated agent through the connectivity of the network; and

resolution means responsive to the resource information from each of said plurality of collecting means for resolving conflicts in resource information from said plurality of collecting means based on said reliability, time and sequence of the resource information from each of said plurality of collecting means;

said resolution means being responsive to the status information about each network resource and operating to create an entry in a resolution database for each new network resource that is identified by said plurality of collecting means;

said resolution means being responsive to the reachability information for updating a reach list that indicates the reachability from a collecting means to network resources.

2. In a communication network having a plurality of resources as nodes or transmission groups between nodes, topology manager apparatus having agents in at least some of the nodes, said apparatus comprising:

a plurality of collecting means, each collecting means for collecting topology information from an associated agent, said topology information indicating the topology of the network as viewed by the associated agent'"'"'s node;

each of said collecting means providing resource information about each resource in the network as viewed by the associated agent node of said collecting means, said resource information indicating the reliability of the resource information;

said collecting means having an analyzing means and a status means;

resolution means responsive to the resource information from each of said collecting means for resolving conflicts in resource information from separate collecting means based on the reliability of the resource information;

said resolution means having a creating means and an updating means;

said analyzing means for analyzing the connectivity of the resources in the network from the topology information provided by the associated agent node;

said status means responsive to said analyzing means for providing status information about each resource included in the topology information from the associated agent node and for providing reachability information indicating whether the resource is reachable from the associated agent node through the connectivity of the network;

said creating means responsive to the status information about each resource for creating an entry in a resolution database for each new resource identified by said collecting means;

said updating means responsive to the reachability information for updating a reach list, the reach list indicating the reachability from said collecting means of resources analyzed by said analyzing means in said collecting means;

means for adding an entry for each resource to the reach list if the resource is reachable from said collecting means and the resource as reached via that collecting means is not on the reach list; and

means for identifying a best reach entry on the reach list for that resource from multiple entries for the resource from said plurality of collecting means, the best reach entry being the reach entry with the most recent update by the reachability information.

4. In a communication network having a plurality of network resources as nodes or transmission groups between, a method for managing the topology of the network using agents in at least some of the nodes to monitor the topology of the network, said method comprising the steps of:

collecting network topology information from each agent by identifying each network resource and the connectivity of each resource in the network as viewed from the agent'"'"'s node;

analyzing the connectivity of each network resource in the network from the topology information provided by each agent and providing reachability status, the reachability status indicating whether the resource is reachable from the agent'"'"'s node through the connectivity of the network;

based on the resource reachability status resolving conflicts in reachability about the same network resource as viewed from different agents;

said resolving step comprises the steps of;

creating an entry in a resolution database for each new resource identified by said collecting step;

adding an entry in a reach list for each new resource; and

updating the reach list based on the reachability status, the reach list indicating the reachability of each network resource as viewed by each agent node; and

said updating step identifying a best reach entry on the reach list for each network resource reachable from the agent nodes, the best reach entry being the entry on the reach list with the most reliable information.

3. The apparatus of claim 4 wherein a collecting means sends a delete message indicating the collecting means will no longer report on said resource and wherein said updating means further comprises:

means in response to the delete message for removing from said reach list a reach entry for the resource as viewed from the deleting collecting means;

means for testing and indicating whether the reach entry being removed is a best reach entry; and

means for identifying a next best reach entry on the reach list for that resource from multiple entries for the resource from said plurality of collecting means.

5. The method of claim 4 wherein a network resource is active but no longer reachable by an agent node'"'"'s transmission groups, said method further comprising the steps of:

appending to a tagged stored resource record in said agent node a delete message if said resource is no longer reachable by said agent node;

analyzing and resolving, at said topology manager, said delete message appended to a tagged stored resource record by deleting from said reach list a reach entry indicating the reachability of said active network resource by said transmission groups;

testing and indicating whether the reach entry being removed from said reach list is a best reach entry; and

identifying a new best reach entry on the reach list for the network resource from multiple entries for the same network resource through other agent nodes.

6. The method of claim 5 wherein said updating step further comprises the steps of:

testing whether or not said reach list entry being removed by said removing step is the only reach list entry for that network resource;

if the entry being removed from said reach list is the only entry for that network resource, marking that network resource with unknown status and setting the best reach entry to null.

7. The method of claim 5 and in addition the steps of:

testing whether or not the network resource, whose entry is being removed from said reach list, is in use by any other agent node;

if the network resource, whose entry is being removed from the reach list, is not in use by any other agent node, deleting the entry for that network resource from said reach list.