Network monitoring is performed using a three-tiered distributed computing system architecture, including a data source tier, a portal tier and a client tier. The data source tier monitors the physical data on the network medium using multiple data collection sources connected to the network. The probes analyze network data and generate fundamental metrics that describe attributes of the network data. The portal tier encapsulates the fundamental metrics along with executable processor objects into data containers having a predefined format. The processor objects contain logic that operates on fundamental metrics contained in the data containers in a manner so as to generate new derived metrics or aggregates of metric data. The data containers may be requested by the client tier, which executes the processor objects and provides a user interface for displaying various types of network information derived from the contents of data containers.