Cisco® Wide Area Application Services (WAAS) reduces the cost and complexity of managing desktops by optimizing virtual desktop delivery over the WAN while avoiding costly bandwidth upgrades. This tested and validated solution improves employee productivity by accelerating the access to virtual desktops and applications along with optimizing branch-office printing. Cisco WAAS increases the scalability and number of Citrix users supported concurrently over the WAN through powerful optimization techniques that reduce bandwidth consumption across users and help ensure consistent, stable performance.
Business Challenges
Customers use desktop virtualization solutions such as Citrix XenDesktop to replace traditional PCs with virtual machines that are managed from the data center to reduce operating costs, increase control of desktop management, and extend business continuity and disaster recovery to enterprise desktops.
However, when desktop virtualization solutions are deployed over the WAN, latency and bandwidth constraints limit the effectiveness of virtual desktop solutions. Customers face the following challenges in deploying virtual desktop solutions for the enterprise:
• Poor performance and lack of predictability over the WAN, affecting employee productivity
• High bandwidth consumption, especially as user counts increase, increasing solution costs
• Limited scalability, reducing the number of users that can be supported concurrently
• Poor performance of centralized printing and increased cost of printing at the branch office
• Poor quality for rich-media websites, especially as the number of users increases at the branch office
Citrix XenDestop Overview
The Citrix XenDesktop virtual desktop infrastructure (VDI) is a desktop virtualization solution that allows users to access their virtual desktops across the network. Figure 1 shows the components of the Citrix XenDesktop solution.
Figure 1. Citrix Desktop Solution
The hosting infrastructure provides a platform for hosting virtual desktops. The hosting infrastructure can be Citrix XenServer, Microsoft Hyper-V, or VMware ESX Server. The Citrix Desktop Delivery Controller (DDC) authenticates users. After authentication, the Citrix DDC identifies the user and dynamically assigns a virtual desktop to that user. The appropriate desktop operating system is streamed into the hosting environment using the built-in provisioning services. The client can be a thin client or a PC running Microsoft Windows operating system. A client will access the DDC using the Citrix Program Neighborhood Agent (PNAgent) or a web browser such as Internet Explorer or Firefox. Clients use the Citrix Independent Computing Architecture (ICA) Protocol to connect to their virtual desktops.
Citrix XenApp Overview
Citrix XenApp is an application virtualization solution that allows users to access applications from their thin PC across the network. Citrix XenApp hosts applications on a Citrix XenApp server located in the data center; this server allows users to access these applications or deliver them in a streamed manner to their local machines, where processing can occur.
Cisco Solution for Virtual Desktops and Applications
To overcome VDI challenges such as WAN latency, packet loss, bandwidth scarcity, scalability, and consistent performance for end users, Cisco provides integrated network control and optimization capabilities.
Figure 2 shows the Cisco Optimization for XenDesktop Solution components.
Figure 2. Cisco Optimization for XenDesktop Solution Components
Cisco WAAS is a comprehensive WAN optimization solution that accelerates applications over the WAN, delivers video to the branch office, and provides local hosting of branch-office IT services. Cisco WAAS allows IT departments to centralize applications and storage in the data center while maintaining LAN-like application performance and to provide locally hosted IT services while reducing the overall branch-office device footprint.
Cisco WAAS enables organizations to achieve four primary IT objectives:
• Application acceleration: Improve productivity of remote employees.
• IT consolidation and WAN optimization: Reduce branch-office IT costs.
• Branch-office IT agility: Provide local branch-office IT services such as printing without additional servers.
• Simplified data protection: Facilitate compliance and business continuity.
Unlike many vendors' WAN optimization products, the Cisco WAAS solution combines proven, widely deployed technology with a proven architecture for network integration and delivers a proven return on investment (ROI). The tested and validated solution from Cisco optimizes virtual desktop delivery.
Cisco WAAS accelerates Citrix ICA to improve performance and reduce bandwidth demands, thereby enabling more confident rollout of VDI across the enterprise.
• Cisco WAAS, deployed on both sides of the WAN, optimizes Citrix ICA traffic between the end user and the data center using a sophisticated combination of TCP optimizations that reduces the negative effects of the WAN, including persistent session-based compression and data-redundancy elimination. Cisco WAAS is used to optimize the Citrix ICA Protocol running over native TCP using Citrix PNAgent, or over HTTP or HTTPS.
• The data center hosts a Cisco WAAS Central Manager, used to manage the Cisco WAAS solution from a central point, reducing operational burdens and costs.
• The branch-office Cisco WAAS appliance provides print services locally to branch-office users by running Microsoft Windows print services.
• Centralized print performance can be dramatically improved and WAN data reduced by using print-specific optimization.
Cisco WAN Edge Router Quality of Service
Efficient delivery of latency- and bandwidth-sensitive applications over the network requires the use of quality-of-service (QoS) techniques. These techniques involve identification of specific application flows and prioritization of their respective traffic. Most routers and switches have built-in QoS support, thus enabling organizations to apply a network-based QoS policy. According to Cisco best practices, the QoS implemented on Cisco IOS® Software routers should take into account the following:
• Classification of VDI traffic must conform to the classification schema used for all enterprise traffic and take advantage of deep packet inspection (DPI) capabilities for accurate payload-based detection of applications. Cisco IOS Network-Based Application Recognition (NBAR) and the modular QoS command-line interface (CLI), or MQC, can accurately identify and apply policy to applications, including VDI, as part of the enterprise QoS architecture.
• Network devices along the path can fully sense and react to traffic congestion. Congestion-avoidance mechanisms such as Weighted Random Early Detection (WRED) take advantage of TCP's congestion-control mechanism. Therefore, QoS policies are best applied in WAN-attached devices such as Cisco IOS Software routers throughout the network, rather than in LAN-attached devices, which cannot see congestion points.
• QoS is applied as an end-to-end function on Cisco IOS Software devices due to their visibility into WAN conditions, ability to perform DPI hierarchical queuing, and other functions that align network resources with application and business requirements. Attempting to apply QoS policies within standalone WAN optimization devices may yield inefficient and unexpected results, as standalone devices have no visibility into true network congestion points. Further, using QoS in standalone WAN optimization devices creates multiple QoS policy management points which introduces complexity in troubleshooting and difficulty in guaranteeing performance due to policy underlap and overlap.
Using Citrix XenDesktop and XenServer to Virtualize and Centralize Desktops
Virtual desktops can be hosted on the Citrix XenServer infrastructure in the data center. Alternatively, virtual desktops can be hosted on VMware Infrastructure 3. The Citrix DDC allows remote-office users to connect to their virtual desktops in the data center.
Solution Benefits
Performance Acceleration
The Cisco WAAS solution accelerates the performance of all applications accessed through Citrix XenDesktop, such as Microsoft PowerPoint, Excel, and Word, as well as Internet and intranet and enterprise websites.
• Cisco WAAS accelerates virtual desktop launch performance by up to 30 percent (Figure 3).
• Cisco WAAS improves Citrix XenDesktop user response time by up to 60 percent when loading Internet and intranet webpages (Figure 4).
• Cisco WAAS improves Citrix XenApp user response time by up to 60 percent when loading Internet and intranet webpages (Figure 5).
Figure 3. Launching Virtual Desktop Using Citrix XenDesktop and XenApp
Figure 4. Web Browsing: Citrix XenDesktop Users
Figure 5. Web Browsing: Citrix XenApp Users
Bandwidth Optimization
Cisco WAAS has been proven to reduce the bandwidth consumption of VDI. As shown in Figure 6, a single enterprise virtual desktop user can consume more than 110 Kbps of bandwidth, increasing WAN costs and degrading the end-user experience. With Cisco WAAS, this bandwidth burden is reduced by almost 50 percent per user, providing better scalability for VDI over the WAN, leading to more confident rollout and broader adoption of the technology.
Figure 6. Citrix XenDesktop WAN Bandwidth Consumption: T1 and 80 ms Latency
Figure 7 shows up to 98 percent WAN bandwidth reduction when the end user uploads and downloads Microsoft Office application files using a full desktop published on a Citrix XenApp server.
Figure 7. WAN Bandwidth Consumption for Citrix XenApp Published Full Desktop
Optimized Printing
Customers face considerable challenges when printing in Citrix XenDesktop environments since the printer at the branch office and the virtual desktops at the data center are separated by the WAN. Using Cisco WAAS, customers have flexible choices for selecting the right print topology for their environments.
Figure 8 shows that Cisco WAAS can accelerate centralized printing through printing-specific optimizations, data reduction, compression, and TCP optimizations to provide tremendous performance improvements in these environments. Cisco WAAS can also support virtual blades, allowing a Microsoft Windows Server to provide print services when deployed on branch-office Cisco WAAS appliances (Cisco Wide Area Virtualization Engines [WAVE]). Cisco WAAS virtual blades can eliminate the need for and cost of additional servers in the branch office.
Figure 8. Centralized Printing Performance
Scalability
A T1 or 1.5-Mbps WAN link can support a maximum of 12 to 14 users using native Citrix XenDesktop with no other traffic on the link, making virtual desktop deployment prohibitively expensive for many customers. Through a combination of optimization techniques, Cisco WAAS increases the number of Citrix XenDesktop users that can be supported on a given infrastructure by two times or more (Figure 9). Cisco WAAS provides uniform, scalable performance for all users. With native Citrix ICA, the user experience rapidly degrades with the addition of users.
Figure 9. Effect of Additional Users on WAN Bandwidth Consumption
Business Benefits
The Cisco WAAS solution optimizes Citrix XenDesktop and XenApp, allowing customers to achieve benefits such as:
• Up to 60 percent better performance for virtual desktops over the WAN
• Up to two times the scalability for Citrix clients without any expensive WAN upgrades
• Up to 60 percent reduction in WAN bandwidth requirements
• Printing optimization over the WAN of up to 98 percent, with the option of a local print server hosted on a Cisco WAVE appliance at the branch office
• Cisco IOS QoS protects the network resources required to support all enterprise applications such as VDI and Voice over IP (VoIP).
Conclusion
Cisco's solution tests represent realistic customer deployments and accurate documentation of such deployments. Cisco recommends that customers take advantage of this fully tested and validated solution to deploy optimized, scalable virtual desktop solutions to reduce infrastructure costs and improve end-user productivity.
