Abstract: An expert system for diagnosing a data communication network is discussed. The expert system includes a knowledge base comprising a plurality of rules pertaining to reactive and proactive diagnosis of the network. The expert system also includes a plurality of modules for processing network-related questions, such as a rule module which uses forward rules to hypothesize whether network problems exist, and which uses backward rules to verify whether the hypothesized network problems exist. The expert system further includes a facilitator for selecting modules to process the questions. The facilitator operates by sending a poll request associated with one of the questions to the modules, analyzing estimates from the modules to identify a module which can most efficiently and effectively process the question, and instructing the identified module to process the question.

Abstract: An expert system for diagnosing data communication networks. The expert system operates according to a landmark data abstraction paradigm, wherein landmarks are interpretations of network data. The landmarks are indicators of network problems. The expert system diagnoses the data communication networks by detecting landmarks and then interpreting the detected landmarks to determine whether network problems exist.

Abstract: System and method for distinguishing duplicate source address replies caused by interconnecting devices connected to a local area network and duplicate source address replies caused by non-interconnecting devices connected to the local area network.The present invention may be implemented through an analyzer. The method includes the following steps: In step 1, the present invention sends a first Address Resolution Request packet for a first Internet Protocol target address. In step 2, all Internet Protocol source address responses replying to the first Address Resolution Request packet are catalogued in a first reply set. In step 3, a second Address Resolution Request packet for a second Internet protocol target address is sent on to the network. In step 4, all Internet Protocol source address responses replying to said second Address Resolution Request packet are catalogued in a second reply set. In step 5, the first reply set is intersected with the second reply set resulting in an intersection set.