Performance Validation for Remote Applications

Supporting the remote workplace
“Sorry, the computers are slow today!” Who has not stood in line at an airline ticket counter or bank teller and heard this apology? For the customer, it’s frustrating. For the business, it can mean lost revenue or even lost customers. For the IT organization responsible for providing the service, it means another difficult discussion with business managers.

Supporting workers in branches and other remote locations is a growing challenge for IT. Survey data from Nemertes Research indicates 27 percent of workers work away from their workgroups, and 62 percent of companies plan to further increase branch office locations in 2007. For IT, the challenge is to provide personal and corporate applications to remote workers while maintaining data security and holding down costs. This has led an increasing number of IT organizations to implement remote application delivery systems based on Citrix Presentation Server or Microsoft® Terminal Services. And Microsoft’s recent release of Remote Desktop Protocol (RDP) 6.0 and planned enhancements to terminal services in Windows Server 2008 promise to drive application delivery into even smaller enterprises.

While application delivery solves many problems, it adds layers of complexity to IT support of a company’s most critical business processes like sales, order processing and customer support. No one would deploy an application without testing for quality and performance. Now—thanks to HP Performance Center software—IT can perform comprehensive performance testing of applications and the complete application delivery system prior to deployment. This paper explains why performance testing of application delivery systems is so critical, how it is done and why nearly four out of five companies using an automated load testing solution use HP Performance Center software.

Application delivery—a solution with its own problems
Traditional desktop computing deploys personal applications like spreadsheet and word processing programs onto each worker’s PC. In addition, client software and browsers provide access to corporate applications running in the data center. This is shown in Figure 1. While fulfilling the concept of “personal computing” that arose with the PC itself, desktop computing challenges IT to keep desktop applications up-to-date, and it distributes sensitive corporate data to locations that usually lack the security of the data center.

The alternative approach is server-based computing enabled by application delivery systems. Server-based computing moves corporate applications, data and personal applications like spreadsheets and word processing to data center servers. There, data is more secure, and applications can be maintained and updated more easily and at less cost than when they are distributed to individual PCs.

Access to server-based applications is provided by application delivery systems like Citrix Presentation Server and Microsoft Terminal Services. These systems remote the user interface of server-based applications to PCs connected locally or over a wide-area network (WAN). A PC user appears to be running an application on Microsoft Windows right on the desktop, but actually a local “thin client” presentation layer is interacting with the application on the server. See Figure 2.

But Figure 2 doesn’t tell the whole story. While solving one set of problems, application delivery presents new ones—it introduces additional hardware and software layers that must be traversed by each keystroke and mouse click (Figure 3).

Most obvious is the presentation services layer itself. It may co-exist on an application server, be off-loaded to a separate piece of hardware or even run on a server farm dedicated to that purpose. But there is more. There must be authentication and security. Application delivery software must include new functionality for connection management and other administration functions. It can include accelerators that compress data for transmission over the WAN. Access to presentation servers is often managed by load balancers. And that’s just within the data center. To get that far, users must often traverse an encrypted virtual private network (VPN) overlaid on the WAN. Like everything in IT, application delivery has its price.

In working with hundreds of customers, our experience indicates remote access solutions are one of the most common causes of unacceptable performance in deployed applications. How do you know—before deployment—response times and transaction throughput will meet user expectations and service level agreements under real-world workloads and transaction volumes? You test it.