Table 4.1. The Cost of Cryptographic Algorithms
Performance Impact with SSL
To study the impact of the SSL algorithms on server performance, we measured
the throughput and latency using trace files in a single Web server environment. The Web
server for this experiment is Apache v2.0 with mod ssl, which provides strong cryptogra
phy for the Apache Web server via the SSL (SSL v2/v3) and TLS (TLS v1) protocols .
The trace files used for the experiment are the Clarknet and NASA trace files. The trace
files have about 3,000,000 client requests for the Web resource. The average file size of
Clarknet is about 15KBytes, while the average file size of NASA is about 28KBytes. We
used 10 workstations as client nodes. One client process runs on each workstation. A
client process sends a new request as soon as it receives the reply for the previous request.
The server node is equipped with 1GHz UltraSPARC llli dual processors running Solaris
2.9 with 4GBytes memory system.
Figure 4.2 depicts the excessive overhead due to SSL offering. Since the average
file size of the NASA trace file is larger than the Clarknet, it shows worse latency and
throughput than the Clarknet trace without SSL. With SSL, the latencies of the Clarknet