We should be able to optimize RDP traffic if compression is disabled on the RDP session itself (i.e. let Riverbed do the compression rather than the client/remote machines). Encryption level should be "low" on the RDP client as well. RDP sessions are pass-through by default (3389 is in the Interactive port label group). Be sure to either remove 3389 from the port label group or (better practice) create an optimization policy to optimize TCP 3389.
Here is a snippet of info from one of the links below:
By default, the Steelhead will pass-through the Microsoft Remote Desktop Protocol (RDP) part of the Interactive port group, and some customers report performance improvements after optimizing it. There is no RDP-aware latency optimization available in the current RiOS releases, so the gains achieved are purely through reduced data transmission through Scalable Data Referencing (SDR).
Optimization of RDP connections requires the sessions be unencrypted and uncompressed.
Compression for RDP sessions can be disabled by configuring the client.
Here are a few Riverbed knowledge base articles that may be helpful:
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