However, even when WAN optimizers have the right traffic to reach their full throughput they can be gated by other factors, such as the number of TCP connections, in the case of most WAN optimizers who offer application-layer optimizations, and IP packet flows, in the case of Silver Peak who offers network-layer optimizations. A WAN optimizer that supports 2,000 connections or flows will stop optimizing traffic when it reaches the 2,001st connection or flow- even where more LAN/WAN throughput is possible.
Silver Peak makes a huge deal of this fact pointing out that it offers 250,000 flows over a single box vs. the "mere" 100,000 TCP connections provided by Riverbed's top end box, the 7050. Requiring plenty of connections or flows may not be an issue for data replication, where there are a limited number of connection or flows between the source and the target, but this can be an issue when a single box in a data center services thousands of users accessing the same servers or hosts.
IT managers should look beyond the hyperbole and realistically assess their own traffic profiles to see how many connections are really needed. Riverbed, for examples, estimate that each VDI user requires three TCP connections so even on a single box an organization would "only" be able to theoretically optimize 20,000 VDI connections - plenty for most organizations.
Traffic performance games and claims have always been something that IT vendors have played and will play. Never has that rule been truer than with WAN optimization. With the ability to save real dollars by improving WAN connections, WAN optimization vendors are encouraged to tout ever greater levels of performance. But those numbers may have little bearing on your reality. As the commercial goes, your mileage though will vary significantly with your experience.
"There are cases where network-layer optimization will perform as well as or better than application-layer optimization. Then there are instances, like in the case of Microsoft CIFS or Citrix ICA, where application-specific optimizations can make a big difference," says Joe Skorupa, research vice president at Gartner, "It all depends on the traffic mix and network conditions."