69

1400

3000

ssl_session

1200

mixed_ssl_session

ssl_bf

2500

1000

mixed_ssl_bf

2000

800

1500

600

Throughput

1000

400

ssl_session

mixed_ssl_session

200

500

Average Request Latency (ms)

ssl_bf

mixed_ssl_bf

0

0

16

14

12

16

14

12

k

Session Period

(a) Latency

(b) Throughput

Fig. 4.10. Latency and Throughput of Homogeneous and Mixed Client Models

The reason why the mixed ssl with bf model shows better latency is that the busy

clients have more requests per session, and thus, the application server can service more

requests with less asymmetric key operations. Since the asymmetric key negotiation

phase is the major performance bottleneck, mixed ssl with bf can yield better perfor 

mance than ssl with bf. mixed ssl with session also has the same advantage, however,

the high skewness due to the busy clients makes imbalance among nodes increasing,

which offsets this advantage.