In a recent newsletter we introduced the concept of Application Delivery 2.0, a major component of which is virtualization. In our last newsletter we discussed the interest that we see in desktop virtualization and what we see as the drivers of that interest. We also pointed out that there are two primary forms of desktop virtualization, client-side and server-side, and discussed the challenges associated with client-side virtualization. We will use this newsletter to discuss the challenges associated with server-side virtualization.
What’s hot in the high-tech hype machine?
With server-side application virtualization, the client device plays the familiar role of a terminal server accessing an application hosted on a central presentation server. The application and data remain hosted in a central server farm that the user typically accesses over a WAN. The typical protocols that are used to support server-side virtualization (for example, ICA and RDP) are far more efficient than protocols such as CIFS, which are well known to be chatty. However, there can still be performance issues associated with ICA and RDP. For example, even relatively small amounts of WAN delay can make moving a mouse appear “jerky”.
The growing interest in desktop virtualization that we discussed in the last newsletter increases the importance of IT organizations deploying WAN optimization controllers (WOC). In order to support desktop virtualization, these WOCs must be capable of tasks such as tuning ICA for interactive traffic; such as mouse/keyboard and screen refresh. It is also becoming more important for the WOC to be able to prioritize, monitor and report on traffic within ICA and RDP streams. In this way it is possible to distinguish interactive traffic from bulk file transfer and apply the appropriate optimization techniques. In addition to ICA and RDP, new display protocols such as PCoIP are beginning to be deployed. It is unclear at this point in time if these protocols will benefit from being optimized by a WOC.
Whether it is done by the WOC itself, or in conjunction with the WOC, supporting application virtualization will require that IT organizations are able to orchestrate the right mix of optimization technologies for each situation. For example, protocols such as ICA and RDP already incorporate a number of compression techniques including bitmap image compression, screen refresh compression, and general data compression. As a result, any compression performed by a WAN optimization appliance must adaptively orchestrate with the hosted virtualization infrastructure to prevent compressing the traffic twice – a condition that can actually increase the size of the compressed payload.
In our next newsletter we will discuss the impact of virtualized appliances. More insight into the changes we expect to see in 2010 can be found in Jim’s recent report on cloud computing.
