Back in 1982, the common perception of virtualization was depicted on the silver screen in the movie “Tron” in which a computer hacker becomes trapped within a mainframe computer system. Now, one sequel and nearly 30 years later, the reality of virtualization is far removed from that realm of science fantasy.

Virtual Desktop Infrastructure, or VDI, is fast becoming a reality in enterprises as a rather popular means to realize sizeable management and cost savings by hosting applications, data and even the desktop operating system within a virtualized environment on a centralized server.

Long-time tech writer, Rob Mitchell recently offered a fairly good primer on the topic of VDI in an issue of Computerworld. In his backgrounder, Mitchell provides a very general overview of how VDI is used, noting:

“To access these remote virtual desktops from home of office, users run special software on a thin client or personal computing device. The client software interacts with the virtual desktop by providing screen updates and sending mouse clicks and keystrokes to the virtual desktop. But everything – the Windows desktop, Windows applications and data – reside in the data center.”

After presenting how persistent and non-persistent VDI operates, Mitchell goes on to describe, in a high-level manner, about personalization or customization of VDI before discussing Application Virtualization, of which he says,

“Application virtualization separates the Windows application from the Windows desktop environment on which the application normally runs. For example, the virtual application does not write to the registry of the Windows desktop on which is resides. This allows administrators to avoid potential conflicts with Windows or other applications, and they can maintain fewer golden images in a nonpersistent VDI environment by moving some applications outside of the base images.”

The reality of virtualization, however, and something Mitchell neglects to discuss in his primer are the problems that can arise when VDI delivers applications and desktops across the WAN.

Real Limits of VDI

The benefits of virtualization can easily be lost if application performance hampers end user productivity, as often happens when virtual applications and desktops are delivered across a WAN. Issues of latency, packet loss and bandwidth cause virtual applications and VDI to be unresponsive and/or unreliable across the WAN.

The poor performance of VDI across the WAN, however, is not due to the VDI architecture; it is due to the network itself. Virtualized applications are very interactive, requiring screen updates and mouse movements to be sent over the WAN using thin-client protocols (for example, Citrix ICA and Microsoft RDP). While these work fine in a Local Area Network (LAN), there are unique challenges when communicating across a WAN that can have an adverse effect on the performance of these protocols, resulting in slow screen refresh rates and occasional session disconnects.

One proven technique to overcome these issues, however, is to deploy WAN optimization (WANop) devices on both ends of a WAN to improve the performance of enterprise applications traversing that WAN.

Real Solutions for VDI

Silver Peak’s WAN acceleration solution helps enterprises reap the rewards of virtualization by overcoming network challenges that impact the performance of VDI applications across the WAN. Silver Peak achieves this using the following optimization techniques:

· Network Acceleration: Silver Peak appliances use various network acceleration techniques to send more data within specific windows and minimize the number of back and forth acknowledgements required prior to sending data. This improves the responsiveness of keystrokes in a virtual environment.

· Network Integrity: Silver Peak fixes WAN quality issues with its Forward Error Correction (FEC) and Packet Order Correction (POC) technologies. FEC is used to rebuild dropped packets on the far end of a WAN link; POC is used to re-sequence packets that are delivered out of order. Both techniques are performed in real-time, eliminating the need to re-transmit data when packet delivery issues occur.

Because the average enterprise has over 80 applications traversing the WAN, Silver Peak’s extensive Quality of Service (QoS) capabilities also play an important role in virtual environments. With Silver Peak, virtual applications and desktops can be prioritized over less important traffic, like Internet browsing. In addition, QoS can guarantee VDI and virtual applications get enough bandwidth across the WAN.

Silver Peak’s Network Memory™ technology inspects all inbound and outbound WAN traffic in real-time, storing a single local instance of data on each appliance. Prior to sending information across the WAN, NX Series appliances compare real-time traffic streams to patterns stored using Network Memory. If a match exists, a short reference pointer is sent to the remote Silver Peak appliance, instructing it to deliver the traffic pattern from its local instance. Repetitive data is never sent across the WAN, saving bandwidth and enabling LAN-like application performance.

While other WAN deduplication solutions are forced to bypass this traffic because they add too much latency, Silver Peak dedupes WAN traffic without adding a significant amount of latency (typically under 1 ms). This is an important differentiation because it enables Silver Peak to work on virtual applications and desktops.