Make Virtualization Work Better Across the WAN

18.11.2008

Latency can be overcome by mitigating the "chattiness" of TCP, the transport protocol used to by virtual applications for communication across the WAN. More specifically, WAN optimization devices can be configured 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.

Loss can be mitigated by rebuilding dropped packets on the far end of a WAN link, and re-sequencing packets that are delivered out of order in real-time. This eliminates the need to re-transmit packets every time they are dropped or delivered out-of-order. By avoiding re-transmissions, virtual applications and desktops appear much more responsive across the WAN.

Bandwidth can be reduced using WAN deduplication. By monitoring all data sent across the WAN, repetitive information can be detected and delivered locally rather than resent across the network. This significantly improves bandwidth utilization in some (but not all) virtualized environments.

3. Set Application Priorities

The average enterprise has more than 80 applications that are accessed across the WAN. That means that critical applications, including terminal services and VDI, are vying for the same resources as less important traffic, such as Internet browsing. Because virtual applications and desktops are sensitive to latency, it often makes sense to prioritize this traffic over other applications using Quality of Service (QoS) techniques. In addition, QoS can guarantee bandwidth for VDI and virtual applications.