Last week at a conference, I was approached by a prospective customer who was also considering an alternative offering from a Riverbed competitor. While this competitive WAN optimization product lacked a number of layer-7 optimization capabilities available in the Riverbed solution (among other things), my questioner was wondering if its significantly-cheaper price made up for its lack of features and capabilities.
More specifically, the prospective customer had questions about the true value of Riverbed's layer-7 optimizations for Exchange. Since his employees were all using Outlook Cache Mode, he reasoned that he didn't need lightning-fast transfer performance for email--his end-users wouldn't notice if emails took a little longer to show up in their Outlook client. He felt that his primary requirement was for the compression and data reduction, since his branch offices all had smaller WAN links and were experiencing network congestion problems. As far as he was concerned, he just needed a product that could deliver more virtual bandwidth, and he was under the impression that most WAN optimization vendors--including the Riverbed competitor that he was considering--would likely meet his requirement.
My response was to point out that Riverbed's layer-7 optimizations go far beyond just addressing latency and protocol chattiness issues--they also address application-specific data encoding processes that are performed by many applications. In the case of Microsoft Exchange, all email attachments are encoded in a MAPI-specific proprietary data format. At the byte-level, these MAPI attachments appear differently than if that same file had been transferred through another protocol such as FTP, CIFS or HTTP (i.e., Sharepoint). Because Riverbed's layer-7 optimization feature recognizes the application-specific data encoding process, it is able to un-do the encoding prior to applying its data reduction algorithms. When using Riverbed, files and other common data that had previously been sent over the network using other applications and protocols will be optimized through "warm" transfers, which greatly boosts overall data reduction results. We refer to this benefit as "cross-protocol" optimization.
The data reduction benefits I am talking about are clearly illustrated in this screenshot submitted by a Riverbed user (click here) for the Performance Hall of Fame. This customer notes that among other things, they replicate their Exchange DB using iSCSI through their Equalogic iSCSI SAN. But note that there is also MAPI optimization taking place between these two sites, which means that the same files are actually traversing the WAN link multiple times--through Exchange/MAPI, as well as through iSCSI for the DR replication.
A competitive product lacking Riverbed's layer-7 optimization capabilities for MAPI would be confused by the encoding process that Exchange performs on all email attachments. Such a product would think there is no data commonality between the MAPI and iSCSI sessions, as well as between the MAPI and CIFS sessions. In addition, the competitive product would also be affected by minor changes to file attachments, such as when an employee edits a few lines of a Word document that he/she just received, and then emails that slightly-modified file back to the originator. The problem here is that even minor changes to a small portion of a file will be rippled through entire length of the file attachment by the Exchange attachment encoding process. The competitive product will think they are two different and unrelated files with no common data, when in fact they are actually the same file with a few minor changes.
Finally, it's important to note that Exchange is far from being the only application that performs application-specific data encoding. Other applications that perform similar actions include Lotus Notes, Oracle E-Business Suite (both JRE and JInitiator), and Citrix ICA. In addition, some applications such as SSL and encrypted MAPI send cryptographically encrypted data. These application traffic types are well represented in most enterprise networks, including that of the Riverbed user providing the screenshot. Riverbed's layer-7 optimizations for these listed applications deliver not only lightning-fast performance by addressing layer-7 protocol chattiness issues, but also superior overall data reduction by recognizing the layer-7 data encoding and/or encryption performed on the data itself by the application.