Enhancing Route Optimization for NAPT Traversal in CYPHONIC: Design and Implementation

The modern Internet encounters challenges in establishing direct communication due to IP version differences and the presence of NAPT. The authors have proposed CYPHONIC to achieve communication connectivity and mobility transparency in IP communication. CYPHONIC facilitates NAPT traversal by leveraging a cloud service to relay device communications. However, this approach introduces challenges such as load concentration on the cloud service and redundant routes. This paper presents a route optimization technique that involves connecting devices through the cloud service and selectively transitioning to direct communication under specific conditions. The proposal focuses on the fact that NAPT involves several types of port translation techniques, a particular combination of which enables direct communication between devices. The introduction of the proposed technique extends the conventional CYPHONIC signaling and adds a function to try to communicate directly with both devices. The evaluation experiment shows whether the proposal is effective enough for the combination of NAPT types, thus clarifying the effectiveness of route optimization.