In this paper, we review the technical details of new features in OpenIGTLink version 2. OpenIGTLink is a free open-source network communication protocol designed for data exchange among devices and software. Since the first release of version 1.0 protocol along with a reference C/C++ library in 2008, the number of developers and users, who use OpenIGTLink in their research projects, have been growing among convincing some commercial companies to implement research interface based on OpenIGTLink their commercial products. However, the message types initially defined for research prototypes does not cover some of functionality in commercial products, thus the protocol needed to be requires refinement in the protocol. The goal of the extension in version 2 is to support such new demands emerged after the release of the initial version, while keeping the protocol as simple as possible. The version 2 protocol has been implemented as an extension of version 1; it is backward compatible in the sense that messages generated by OpenIGTLink version 2 compliant software can be received by version 1 compliant software.