Transport mechanism can influence test system implementation and test suite design. Good transport mechanism can shield the information of implementation under test (IUT) to test suite designer and simplify test configuration. Based on the idea that test suite design and test transport be independent, the technique that combines communication entity with network interface is proposed to implement transport mechanism. The logical test interfaces are defined by network interfaces. The test packets are received/sent by communication entity, which makes the lower service provider transparent to test suite. Manual configuration isn't necessary before testing. By setting appropriate identifier information in the object of network interface, the concurrent test ability of test system is independent of system configuration. It is successful to apply the transport mechanism to IPv6 protocol conformance testing.