The status updates, which are acquired from IP Availability Manager and from periodic monitoring, serve as input to the data model in the Network Protocol Manager for IS-IS repository. Network Protocol Manager for IS-IS applies the status updates to the appropriate attributes of the corresponding IS-IS objects in the data model.

The data model involves a codebook that is created by VMware engineers as a result of their knowledge of IP and IS-IS networks. The codebook identifies IP and IS-IS problems and their symptoms, and presents a causality mapping between each problem and its set of symptoms.

Network Protocol Manager for IS-IS diagnoses root-cause availability problems by finding the problems in the codebook that can best explain the observed symptoms. It also uses the codebook to correlate the impact of a root-cause problem on the IS-IS objects that are either inaccessible or impaired as a result of the root-cause problem. The root-cause problem is either a physical-transport problem that is diagnosed by IP Availability Manager or an IS-IS problem that is diagnosed by Network Protocol Manager for IS-IS.