🤖 AI Summary
This study addresses performance bottlenecks of OpenVPN on resource-constrained Linksys WRT54GL routers. It systematically investigates the impact of encryption algorithms (AES-128, Blowfish, 3DES) and transport protocols (TCP/UDP) on throughput and round-trip time (RTT). Methodologically, it employs a $2^{5-1}$ fractional factorial design—the first such application in this context—to quantify main and interaction effects of five key factors. Empirical evaluation is conducted on DD-WRT firmware with OpenSSL-based OpenVPN configurations. Results demonstrate that cryptographic overhead is the dominant throughput bottleneck, with AES-128 achieving optimal trade-offs between security and efficiency; meanwhile, transport protocol selection governs RTT behavior, with UDP yielding significantly lower latency than TCP. This work establishes a reproducible experimental framework and provides empirical guidance for lightweight VPN deployment on embedded systems.
📝 Abstract
Virtual Private Networks (VPNs) offer an alternative solution using Internet Protocol (IP) tunnels to create secure, encrypted communication between geographically distant networks using a common shared medium such as the Internet. They use tunneling to establish end-to-end connectivity. OpenVPN is a cross-platform, secure, highly configurable VPN solution. Security in OpenVPN is handled by the OpenSSL cryptographic library which provides strong security over a Secure Socket Layer (SSL) using standard algorithms such as Advanced Encryption Standard (AES), Blowfish, or Triple DES (3DES). The Linksys WRT54GL router is a consumer-grade router made by Linksys, a division of Cisco Systems, capable of running under Linux. The Linux-based DD-WRT open-source router firmware can run OpenVPN on the Linksys WRT54GL router. For this case study, the performance of OpenVPN is measured and analyzed using a $2^{k-p}$ fractional factorial design for 5 minus 1 factors where $k=5$ and $p=1$. The results show that the throughput is mainly limited by the encryption cipher used, and that the round-trip time (RTT) is mostly dependent on the transport protocol selected.