As noted in the introduction to application delivery, new challenges have started to drive the movement to Application Delivery 2.0. These application delivery challenges and the requisite wide area network (WAN) optimization controller (WOC) functionality are described below.
Simplification of the branch office
As noted, part of early application delivery, or Application Delivery 1.0, was characterized by the nascent trend to remove IT resources like servers from branch offices. As part of newer application delivery techniques, Application Delivery 2.0, that trend is accelerating as IT organizations are continuing to remove servers from branch offices. In addition, half of IT organizations have begun to implement virtualized applications and desktops and another 25% expect to do so in 2010 (noted in my Cloud computing risk mitigation guide).
Application virtualization centralizes the management of desktop applications, including applications that are streamed on-demand to client devices (client-side virtualized applications) and applications hosted at the central site (server-side virtualized applications). In both of these models, the application is virtualized in that it appears to be installed on the client device when that is not actually the case.
Client-side application virtualization comprises two primary functions: application isolation and application streaming. Application isolation is based on the encapsulation of the application by an abstraction layer inserted between the application and the operating system of the client system. Application streaming is the process whereby the virtualized application is delivered to an end system's isolation environment from a centralized application repository in an on-demand fashion.
Application streaming creates some significant performance problems that require the deployment of a WOC. For example, the code for streamed applications is typically transferred via a distributed file system protocol, such as CIFS, which is known to be a chatty protocol. Hence, in order to effectively support application streaming, IT organizations need to be able to optimize the performance of protocols such as CIFS, MAPI, HTTP and TCP. IT organizations also need to implement techniques that reduce the bandwidth requirements of application streaming. For example, by using a WOC, it is possible to cache the virtual application code at the client's site. Caching greatly reduces the volume of traffic for client-side virtualized applications, and it allows applications to run locally in the event of network outages.
With server-side application virtualization, the client device plays the familiar role of a terminal server accessing an application or desktop hosted on a central presentation server. The application and data remain hosted in a central server farm that the user typically accesses over a wide area network (WAN). The typical protocols that are used to support server-side virtualization for desktops and applications (i.e., ICA and RDP) are far more efficient than protocols such as CIFS. However, even relatively small amounts of WAN delay can make moving a mouse appear jerky; and, unfortunately, users expect the same experience independent of the underlying technology. Given the growing interest in desktop and application virtualization, it is becoming increasingly important for IT organizations to deploy a WOC that is capable of tuning these protocols for interactive traffic such as mouse/keyboard and screen refresh. It is also becoming more important 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 time whether 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 can apply the right mix of optimization technologies for each situation. For example, pre-staging and storing large virtual desktop images on the WOC at the branch office must be done in an orchestrated fashion with the corresponding resources in the data center. Another example of the importance of orchestration is the growing requirement to automatically apply the right mix of optimization technologies. 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 avoid compressing the traffic twice -- a condition that can actually increase the size of the compressed payload.
Few IT organizations will actually implement a truly server-less office. Some will leave servers in the branch office; others will support their branch office IT requirements based on one of the following:
- A router that supports virtual machines
- A branch office box (BOB)
- An appliance-based WOC that supports virtual machines
If the IT organization chooses to implement a virtualized WOC in the branch office, that virtualized WOC must integrate into whatever platform (server, router, BOB) remains in the branch office. Whether or not the WOC is virtualized, in order to meet the needs of most IT organizations, the WOC must be tightly integrated with the appropriate Microsoft solutions and must be capable of being managed centrally as it is becoming increasingly rare to have IT staff in branch offices. IT organizations also need the ability to create and enforce policies around the question of which users have access to which applications and data -- whether these policies are provided by the WOC or in conjunction with the WOC. The creation and enforcement of these policies was somewhat important as part of Application Delivery 1.0. These functions are a critical component of Application Delivery 2.0 in order to ensure that both client-side and server-side virtualized applications are accessed only by people who are authorized to do so.
Continue reading this guide to learn how WAN optimization controllers are used in Application Delivery 2.0:
- Introduction to application delivery
- Improving virtualized applications
- Cloud computing adoption's effects on application traffic
- Optimizing mobile application delivery
- Optimizing virtualized servers
Dr. Jim Metzler, principal at Ashton Metzler and Associates, is a widely recognized authority on network technology and its business applications. In more than 28 years of experience, Jim has helped numerous vendors refine product and service strategies and has helped enterprises evolve network infrastructures. He has directed and conducted market research at a major industry analyst firm and run a consulting firm. Jim holds a Ph.D. in numerical analysis from Boston University. He is co-author of the book Layer 3 Switching: A Guide for IT Professionals (Prentice Hall).
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