At first glance, encrypted Secure Sockets Layer traffic wouldn’t seem like an obvious candidate for application acceleration, given its lack of compressibility and the invisibility of contents to optimization engines.

But Blue Coat and Riverbed appliances do support SSL optimization and Cisco and Silver Peak say it’s on their to-do list. Even with SSL’s secret nature, it’s still possible to speed up traffic.

The Blue Coat and Riverbed devices act as intermediate SSL devices. After we generated, signed and installed certificates on each vendor’s appliance, they intercepted and de-encrypted SSL sessions, applied optimizations, then re-encrypted traffic and sent it on its way.

We tested these capabilities with Spirent’s Avalanche and Reflector in a configuration nearly identical to our Web tests. Unfortunately, results were underwhelming (see “SSL Acceleration,” on-line chart at www.nwDocfinder.com//xxxx. Link again to 0813WANNumbersall.xls).

The Blue Coat and Riverbed appliances offered only marginal improvement over the no-device baselines, and performance with Blue Coat’s device actually decreased when we tested with more users. It’s possible this was because of erratic Address Resolution Protocol table behavior we observed in the Blue Coat devices.

For its part, Riverbed suspects its results might be the result of its appliances simply passing through traffic rather than trying to optimize it, something we did not verify in testing.

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