High-speed networks such as ATM, Myrinet, and Gigabit Ethernet are available today, and many researchers make efforts to enhance the performance of end-to-end communication on these high-speed networks. One of the efforts is to develop new light-weight communication primitives for high-speed network. However the latency of the new primitives has not been characterized thoroughly, partly because existing measurement methodologies do not take into account the features of high-speed networks. Therefore, there are only incomplete comparisons of the new primitives and traditional protocols, and they cannot really prove the usefulness of new primitives. In order to address this issue, this paper suggests a new measurement methodology and uses the methodology to perform a detailed latency analysis of UDP and a light-weight primitive, called BPI, on Myrinet. Our results clearly show the difference of per-byte overhead between BPI and UDP. A surprising result is that BPI is found to be slower than UDP for 4KB or larger data size.