Citrix XenApp has helped virtualized applications show their mettle in the enterprise, bringing the promise of thin-client technology and portable applications to an increasing number of users. However -- as with most technologies -- deployments can encounter problems.
With virtualized applications, the leading problem seems to be related to bandwidth. For Citrix XenApp to deliver an acceptable end-user experience, reliable and fast network communications are a must. Unfortunately, guaranteeing effective data rates over public networks (such as the Internet) can be nearly impossible, and private, high-speed connections can be extremely expensive. Both cost and bandwidth can derail XenApp deployments.
However, there are remedies for limited-bandwidth and high-latency connections. Several products focus on accelerating performance of XenApp sessions and optimizing wide-area network (WAN) connections, and each has its particular nuances and capabilities. The first step in addressing bandwidth or latency issues is to understand the available options and how they would integrate into the enterprise.
Although many vendors -- large and small -- offer a multitude of solutions that fall under the WAN optimization umbrella, there are four industry leaders: Citrix, Cisco, Blue Coat and Riverbed.
Here is a closer look at what these companies offer for WAN optimization and application acceleration.
Citrix has some specialized products that are engineered to improve XenApp performance. The Citrix Branch Repeater is a hardware appliance that incorporates technology to optimize the transmission of virtualized applications to branch offices. Branch Repeater basically works like an application-delivery cache, which uses compression to maximize the amount of data presented and retrieved from the thin client. In that fashion, Branch Repeater improves the performance of any virtualized application being delivered to an endpoint. Citrix has additional names for the elements of the technology -- HDX IntelliCache and HDX Broadcast. The goal of HDX IntelliCache and HDX Broadcast is to maintain what Citrix calls the "high-definition experience" for users. In other words, virtualized applications should perform as well as local applications. The Citrix Branch Repeater is available in many configurations and sizes, based upon the number of users and the bandwidth needed. The product can range in price from several thousand dollars to tens of thousands of dollars.
Riverbed Technology offers several appliances tuned for WAN optimization. The company's Steelhead family of appliances combines several optimization technologies to increase performance. They are powered by the Riverbed Optimization System (RiOS), which combines compression, caching, IP optimization and several other capabilities to accelerate applications. Although RiOS is not designed as a Citrix-only solution, it can greatly improve the performance of virtualized applications delivered via XenApp. Steelhead appliances are fully scalable and come in a range of sizes to meet the needs of different-sized remote offices.
Cisco has developed a system for WAN optimization and application acceleration that incorporates several of the company's proprietary products. Collectively, the technology is called wide-area application services (WAAS) and is designed to optimize the performance of any TCP-based app operating in a WAN environment while preserving and strengthening branch security. WAAS combines WAN optimization, acceleration of TCP-based applications and Cisco's Wide Area File Services (WAFS) in a single appliance or blade. WAAS is also available in multiple shapes and sizes to scale to an organization's needs.
Blue Coat Systems
Blue Coat offers a few products under the umbrella of WAN optimization. Ideally, such a product improves virtualized application performance by combining several technologies that reduce latency, compress data, cache traffic and manage bandwidth. BlueCoat offers its ProxySG appliance in an Acceleration Edition, which the company claims creates a fast application-delivery infrastructure. When deployed at the core and edges of an enterprise's infrastructure ProxySG can improve user productivity and reduce bandwidth expense, according to BlueCoat.
Blue Coat combines compression, byte-caching and object-caching technologies to reduce the bandwidth needed for applications and minimize the impact of latency. Blue Coat accelerates apps by optimizing traffic, conserving bandwidth, and metering or blocking recreational apps. External applications in particular can benefit from HTTP optimization and caching, along with advanced Secure Sockets Layer/Transport Layer Security acceleration. Those capabilities help the product to deliver LAN-like application performance to remote users and branch offices and improve performance for streaming audio, video and other rich-media applications. Like the other WAN acceleration appliances, ProxySG is available in multiple configurations to meet the needs of businesses of different sizes.
Each of the products listed above has features to make XenApp virtualized applications perform better. In addition, they can help other applications and services to achieve maximum performance over a LAN.
ABOUT THE AUTHOR:
Frank Ohlhorst is an IT journalist who has also served as a network administrator and applications programmer before forming his own computer consulting firm.
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