We were discussing Riverbed Operating System (RiOS) technical concepts. With file servers and Email systems, RiOS has another optimization. This is the transparent pre-population. RiOS can transfer segments of file or email to the remote appliance before it is requested by any client. The initial access of a new file or email is therefore accelerated. When the first client calls in, the new file or email may not have made it across WAN and  the client could suffer a miss penalty. This is avoided if the file or email is pre-populated. There is no agent involved just that the segments are sent earlier. This is particularly helpful for emails with attachments. As emails arrive, their components are pulled across the WAN with all the RiOS acceleration techniques. In addition, for emails, RiOS keeps the Exchange TCP connection alive. This technique avoids big surges in email requests, such as the spikes that occur at the start of a work day and can bring the rest of a branch office's applications to a halt. Contrast this approach with the MAPI recommendation to use Cache Mode.  There is no data reduction techniques applied to the traffic in Cache Mode since there is nothing to accelerate email retrieval for users receiving large attachments or re-syncing their inbox. Consequently there is no benefits to network utilization with Cache Mode where as with references and segments used for deduplication and acceleration, there is significant improvement. Moreover, RiOS techniques can work with both Cache Mode as well as non-Cache Mode for Exchange servers. RiOS is therefore able to deliver optimizations for both OutlookAnywhere and MAPI clients. Finally, RiOS support for encrypted traffic optimizes it for deployments where Exchange Server has encrypted mode enabled by default.
RiOS doesn't avoid caching. In fact one of the performance improvement features for both HTTP and HTTPS traffic is that RiOS has an object-prefetch table to cache static web content which improves on reassembling from data references. This still allows for fresh transfers. In addition, RIOS supports the "If-Modified" request and "Not-Modified" responses which directs the clients to use their own local web browser cache avoiding WAN requests and minimizing delay for end-users.