The system and method send test packets into a network between a plurality of source and destination nodes. Each source node is also a destination node. The test packet contains an additional field (e.g., a field of particular interest to an application or user) that is subject to being modified as the test packet traverses the network (e.g., a DSCP marking). A determination is made if the additional field has changed; if so, the network node that changed the additional field is identified and displayed to a user in a matrix display of the source nodes and destination nodes. This allows a user to identify situations where changes in the additional field may indicate that the test packet is being routed in the network at a priority that is outside of a Service Level Agreement.