We introduce a new class of Model Based Metrics designed to assess if a complete Internet path can be expected to meet a predefined Target Transport Performance by applying a suite of IP diagnostic tests to successive subpaths. The subpath-at-a-time tests can be robustly applied to key infrastructure, such as interconnects or even individual devices, to accurately detect if any part of the infrastructure will prevent paths traversing it from meeting the Target Transport Performance. For Bulk Transport Capacity, the IP diagnostics are built on test streams that mimic TCP over the complete path and statistical criteria for evaluating the packet transfer statistics of those streams. The temporal structure of the test stream (bursts, etc) mimic TCP or other transport protocol carrying bulk data over a long path but are constructed to be independent of the details of the subpath under test, end systems or applications. Likewise the success criteria evaluates the packet transfer statistics of the subpath against criteria determined by protocol performance models applied to the Target Transport Performance of the complete path. The success criteria also does not depend on the details of the subpath, end systems or application. Model Based Metrics exhibit several important new properties not present in other Bulk Transport Capacity Metrics, including the ability to reason about concatenated or overlapping subpaths. The results are vantage independent which is critical for supporting independent validation of tests by comparing results from multiple measurement points. This document does not define the IP diagnostic tests, but provides a framework for designing suites of IP diagnostic tests that are tailored to confirming that infrastructure can meet the predetermined Target Transport Performance.