This Recommendation describes a model for evaluating multimedia transmission performance over an IP network. It is a statistical model in which likelihood of occurrence values are assigned to all network elements and impairments. Test results using these statistical models are expressed in terms of Network Model Coverage. . These results are unconditional - not dependent on the a priori specification of any network elements or impairments. Testing to a comprehensive statistical model suggests how communications devices may perform over an IP network in terms of Network Model Coverage. This standard focuses on the impact of impairments on Layer 3 performance. IP streams from any type of network device can be evaluated using this model. Emphasis is given to the fact that manufacturers of communications equipment and service providers are interested in a specification that accurately models the IP network characteristics that determine performance. Evaluators desire a definitive set of simple tests that properly measure the performance of communications devices from various manufacturers. Therefore, the objective of this document is to define a technology-independent model that is representative of the IP network, that can be simulated at reasonable complexity and that facilitates practical evaluation times.