There are many paths where users can communicate with wired and/or wireless links. Multiple links are used at the same time and in the same place. In these situations, users can select a better path by measuring the path characteristics. This is also issue in Mobile IP triangle routing [13][14]. Upload and download traffic is significantly different at short period. For path selection, a one-way measurement is needed, thus this paper proposes a one-way differential delay which can be used easily to select a better path. We have developed a prototype and simulation system.