dynamic content is not an efficient option like caching the static content. Although dis
tributed Web server design has been a major research topic to improve the throughput
and response time [13, 58, 49], to the best of our knowledge, there has been no previous
effort to improve performance in cluster based application servers with SSL connections.
In this chapter, first, we investigate the impact of SSL offering in cluster based
network servers, focusing on application servers, which mainly provide dynamic content.
Second, we show the possible performance improvement when the SSL session reuse
scheme is utilized in cluster based servers. The SSL session reuse scheme has only been
tested on a single Web server node in the previous research . Third, we propose a
backend forwarding mechanism by exploiting low overhead user level communication to
fully enhance the SSL enabled network server performance.
To this end, we compare three distribution models in clusters: RR (Round Robin),
ssl with session and ssl with bf (backend forwarding). The RR model, widely used in
Web clusters, distributes requests from clients to servers using the Round Robin scheme.
ssl with session uses a more sophisticated distribution algorithm, in which subsequent
requests of the same client are forwarded to the same server, avoiding expensive SSL setup
costs. The proposed ssl with bf uses the same distribution policy as the ssl with session,
but includes an intelligent load balancing scheme that forwards client requests from a
heavily loaded backend node to a lightly loaded node to improve the utilization across all
nodes. This policy uses the underlying user level communication for fast communication.
Extensive performance analyses with various workload and system configura
tions are summarized as follows: First, schemes with reusable sessions, deployed in
the ssl with session and ssl with bf models, are essential to minimize the SSL overhead.