A method and apparatus for testing network performance are provided. In data provided by an application on a first host for transport or communication to an application associated with a second host according to a first data transport protocol is intercepted at the first host and wrapped or encapsulated in a test data packet formatted according to a second data transport protocol. The test data packet formatted according to the second data transport protocol includes, in addition to data comprising all or a portion of the original data packet, instrumentation information. The test data packet is then delivered to the second host, which unpacks the original data packet and the instrumentation information. A response packet containing instrumentation information may be sent from the second host to the first host to provide roundtrip performance metrics.