A load balancing scheme for cluster-based secure network servers

Although the Secure Sockets Layer (SSL) is the most popular protocol to provide a secure channel between a client and a cluster-based network server, its high overhead degrades the server performance considerably, and thus, affects the server scalability. Therefore, improving the performance of SSL-enabled network servers is critical for designing scalable and high performance data centers. In this paper, we examine the impact of SSL offering and SSL-session aware distribution in cluster-based network servers. We propose a backend forwarding scheme, called ssl_with_bf, that employs a low-overhead user-level communication mechanism like VIA to achieve good load balance among server nodes. We compare three distribution models for network servers: Round Robin (RR), ssl_with_session and ssl_with_bf through simulation. The experimental results with 16-node and 32-node cluster configurations show that while session reuse of ssl_with_session is critical to improve the performance of application servers, the proposed backend forwarding scheme can further enhance the performance due to better load balancing. The ssl_with_bf scheme can minimize average latency by about 40% and improve throughput across a variety of workloads.