If It Isn't Broken...
This release of RiOS refines an already stable and well rounded offering, adding and tweaking instead of ripping and replacing. One of the items that falls into the "tweaked" category is secure Web traffic (HTTPS). It is now easier to configure Steelheads to optimize SSL traffic than it was with RiOS 4.
Previously, admins had to manually establish a trust between appliances by copying certificates between Steelheads. Now, when a Steelhead tries to optimize HTTPS between an acceleration pair, the remote Steelhead will automatically send its certificate to the other Steelhead, which in turn gray-lists the appliance. An admin then either accepts or rejects the gray-listed appliance. If the appliance is rejected (blacklisted), it will not be able to optimize SSL traffic but will instead simply pass it on over the WAN un-optimized. By creating this automated certificate facility, SSL configuration is much easier and less prone to error while allowing IT to maintain control over how and when HTTPS traffic is optimized.
Standard HTTP traffic also received a performance upgrade in RiOS 5. RiOS 4's HTTP optimization worked well with static Web content but didn't provide much help with dynamic. RiOS 5's HTTP engine now includes two new features specifically tailored to dynamic Web pages; Parse & Pre-fetch and Metadata Response. Parse & Pre-fetch parses the HTML page, downloads the objects, and stores them on the client side Steelhead for faster access. Metadata Response is useful when cache-control headers are involved. For example, if the browser sends out an "if modified since" request, the client-side Steelhead can respond to it locally, thus reducing the round trip across the WAN.
Another unique feature to RiOS 5 is its capability of accelerating native Exchange 2007 traffic. I tested this feature with a Windows Vista client and Office 2007 saving an attachment from the Exchange message store locally. I also copied the attachment to a file share across the WAN and saw the file served out of the local cache, reducing overall transfer time.