Dell™ Reference Architecture for Microsoft®
Lync® on Citrix® XenDesktop® 5.6
Table of Contents
1 Introduction .................................................................................................................................. 3
1.1 Purpose of this document ................................................................................................................................. 3
1.2 Scope ........................................................................................................................................................................... 3
2 Solution Architecture Overview............................................................................................. 4
2.1 Introduction ............................................................................................................................................................ 4
2.2 Architectural Overview ...................................................................................................................................... 4
2.2.1 Overview of Solution Components ...................................................................................................... 5
2.2.2 Design Challenges ....................................................................................................................................... 5
3 Hardware Components ............................................................................................................. 7
3.1 Dell PowerEdge R720 Servers......................................................................................................................... 7
3.1.1 Local Storage ................................................................................................................................................. 7
3.2 Dell Wyse Endpoints ............................................................................................................................................ 8
3.2.1 Dell Wyse R Class Cloud Clients ............................................................................................................ 8
3.2.2 Dell Wyse Z Class Clients ......................................................................................................................... 8
3.2.3 Dell Wyse D Class Thin Clients .............................................................................................................. 9
3.3 Force10 S55 Network Switch .......................................................................................................................... 9
3.4 Network Topology ............................................................................................................................................. 10
4 Software Components .............................................................................................................. 11
4.1 Overview ................................................................................................................................................................ 11
4.2 Microsoft Windows Server® 2008 R2 SP1 and 2012 with Hyper-V® and Microsoft®
SCVMM ............................................................................................................................................................................ 11
4.3 Microsoft® Lync® Server 2010 ..................................................................................................................... 11
4.4 Citrix XenDesktop .............................................................................................................................................. 13
4.5 Citrix ICA Protocol and HDX .......................................................................................................................... 14
4.6 Citrix HDX RealTime Optimization Pack 1.2 for Microsoft® Lync® ............................................ 15
4.6.1 How the Optimization Pack Works .................................................................................................. 15
4.6.2 Data Flow with the Optimization Pack ........................................................................................... 16
4.6.3 Without the Optimization Pack ......................................................................................................... 17
5 Test Description, Methodology, and Results ................................................................... 18
5.1 Overview ................................................................................................................................................................ 18
5.2 Test Configuration ............................................................................................................................................. 18
5.2.1 Configuration Details.............................................................................................................................. 18
5.3 Test procedures .................................................................................................................................................. 19
5.4 Test Results and Data Analysis .................................................................................................................... 20
5.4.1 Data Analysis: Audio Conferencing Workload ............................................................................ 20
5.4.2 Data Analysis: Video Conferencing Workload ............................................................................ 23
6 Conclusion.................................................................................................................................... 26
References ....................................................................................................................................... 27
About the Authors......................................................................................................................... 28
1
1.1
Introduction
Purpose of this document
This document describes a reference architecture and performance testing for Microsoft® Lync® 2010
client applications running within a Citrix® XenDesktop® 5.6 virtual desktop environment using Dell
servers and thin clients. Dell™ PowerEdge™ servers hosted the Citrix XenDesktop virtual desktops, as
well as the application and infrastructure services. Dell Wyse® thin client devices were the user
endpoint devices.
The purpose of the testing was two-fold: (1) to assess Microsoft® Lync®2010 client application
performance using Citrix virtual desktops on the thin clients, and (2) to examine the impact of the
Citrix® HDX™ RealTime Optimization Pack for Microsoft ® Lync®, Version 1.2. This paper highlights
performance metrics and user densities measured with and without the Citrix HDX RealTime
Optimization Pack.
1.2
Scope
Relative to delivering Microsoft® Lync® 2010 applications within a Citrix XenDesktop environment,
the objectives of this document are to:
● Define the technical architecture for the solution.
● Define the hardware requirements that supported the design.
● Define any design constraints.
● Discuss relevant risks, issues, assumptions and concessions.
● Provide a breakdown of key design elements such that the reader receives an incremental or
modular explanation of the design.
● Provide solution sizing, scaling, and component selection guidelines.
2
2.1
Solution Architecture Overview
Introduction
Collaboration is increasingly important to today’s workforce and operational practices. Organizations
find that improved communication and strong collaboration among employees, business partners, and
customers improves operational efficiency, increases productivity, and reduces costs, helping to
contribute to business success. To facilitate effective collaboration, many companies are implementing
Microsoft® Lync® to provide Unified Communications services: instant messaging (IM), application
sharing, audio/video/web conferencing, and VoIP telephony. Microsoft® Lync® can help companies
reduce travel and mobile phone expenses, lowering operational budgets while increasing
communication and creativity among employees and key stakeholders.
Dell and Citrix have developed a Unified Communications (UC) architecture to help organizations
achieve cost savings and efficiencies when enabling collaborative services. This virtualized UC
architecture supports Microsoft® Lync® 2010 client applications that execute within a Citrix
XenDesktop VDI environment. Citrix XenDesktop provides on-demand enterprise delivery of
Microsoft Windows® applications, including Microsoft® Lync®, allowing desktops to be virtualized,
centralized, and managed within the corporate datacenter for better security, administrative
simplicity, and reduced costs.
This paper describes a virtualized UC architecture for deploying Microsoft® Lync®2010 client
applications within Citrix XenDesktop. It presents performance and scalability tests jointly conducted
by Citrix and Dell engineers, and analyzes the results of that testing to help customers confidently size
virtualized deployments for Microsoft® Lync® client delivery.
2.2
Architectural Overview
In testing of this architecture, three Dell PowerEdge server platforms hosted infrastructure services,
Microsoft® Lync® services, and Citrix XenDesktop services (Figure 1). A variety of Dell Wyse thin
client devices acted as user endpoints for the provided application services.
DC1
DDC1
VMs Hosted
SQL1
VMM1
Dell Poweredge
720 Infrastructure
Hyper-V server 1
10 x Win7 VMs without
Optimization pack
VMs Hosted
. ICA / HDX .
10 x Win7 VMs with
Optimization pack 1.2
Wyse Thin
Clients
Dell Poweredge 720
Compute Hyper-V
server for VDI VM s
LYNCFE
LYNCBE
VMs Hosted
LYNCFS
LYNCMA
Dell Poweredge
720 Infrastructure
Hyper-V server 2
Figure 1. Dell/Citrix architecture for Microsoft® Lync®.
The architecture was tested to demonstrate the efficient delivery of Microsoft® Lync® client
applications, and to determine the impact of the add-on Citrix HDX RealTime Optimization Pack. Test
results presented in this paper can help to guide customers in sizing actual deployments.
2.2.1
Overview of Solution Components
The key components in the reference architecture include:
● Dell PowerEdge™ R720 Servers. These dual-socket platforms run the Intel® Xeon® E52600 family of processors, with up to 24 DIMMs for a maximum of 768GB RAM, and support for
up to 16 2.5” SAS disks, providing uncompromising performance and scalability in a compact 2U
form factor. The Intel® Xeon® E5-2600 processor family features 32-nanometer process
technology with up to 8 cores per processor, delivering fast processing for compute-intensive
multimedia applications.
● Dell Wyse Thin and Cloud Clients. Dell Wyse thin client devices are well suited to virtual
desktop environments because they bring the benefits of simplified security and centralized
management. A variety of thin and cloud client devices are available, including those that
support high definition multimedia graphics, voice, and video for collaborative services.
● Citrix XenDesktop. Citrix XenDesktop is a desktop virtualization solution that transforms
Windows desktops and applications into an on-demand VDI service. With XenDesktop, you can
securely deliver Windows, web, and Software-as-a-Service (SaaS) applications, or full virtual
desktops to PCs, Macs, tablets, smartphones, laptops, and thin clients—all with a high-definition
user experience. In this architecture, Citrix XenDesktop provided pooled desktops for a variety
of Dell Wyse thin client devices.
● Citrix HDX RealTime Optimization Pack for Microsoft® Lync®, Version 1.2. This package
supports clear, crisp high-definition video and audio conferencing in conjunction with
Microsoft® Lync®. Testing of this architecture compared the performance of Microsoft® Lync®
workloads with and without the Optimization Pack to understand impact on user densities.
● Microsoft Windows Server® 2008 R2 Service Pack 1 and Microsoft Windows Server® 2012
Enterprise Editions with Hyper-V® and SCVMM. Virtual machines (VMs) were hosted on
Microsoft Windows Server® 2008 R2 Service Pack 1 and Microsoft Windows Server® 2012 with
Hyper-V®. Microsoft System Center 2012 Virtual Machine Manager (SCVMM) was used to
manage the environment.
● Microsoft® Lync® Server 2010 Enterprise Edition. Microsoft® Lync® supports instant
messaging, shared applications, audio and video conferencing, and interactive voice. To take
advantage of these collaborative capabilities, users access a Lync client that connects to a frontend Lync server to establish communications with other users.
2.2.2
Design Challenges
Microsoft® Lync® imposes a computationally intensive workload on servers, especially because of its
requirement to drive real-time audio and video output across low-bandwidth networks. To meet
requirements for voice and video conferencing, the VDI architecture must be capable of fast compute
processing, low latencies, high throughput, and fast video rendering.
To understand the capabilities of the design and the user densities that it can support, testing focused
on the highly demanding workloads of audio and video conferencing. Since instant messaging (IM)
imposes a nominal impact on performance and user densities, it was not part of the tested workload.
2.2.2.1
Citrix ICA Protocol and Citrix HDX RealTime Optimization Pack 1.2
To deliver high-quality multimedia capabilities for collaborative tools like Microsoft® Lync®, Citrix
XenDesktop uses an efficient Citrix-developed core protocol, ICA (Independent Computing
Architecture), which includes HDX technology to create a rich end-user experience. Citrix XenDesktop
relies on the ICA protocol and HDX to pass data between XenDesktop servers and client endpoint
devices. The protocol natively applies compression and optimizations to address many challenges
associated with network latencies, taking advantage of endpoint functionality and rendering locally or
remotely depending on endpoint capabilities. Installing the Citrix HDX RealTime Optimization Pack
for Microsoft® Lync®, Version 1.2 adds further optimizations that take advantage of the local
capabilities of Dell Wyse thin clients, accelerating performance of collaborative voice/video services.
2.2.2.2
Dell Infrastructure Technologies for VDI and Unified Communications
While the Citrix XenDesktop optimizations are important, the scaling of Microsoft® Lync® clients also
depends on powerful servers and capabilities that are inherent in the user endpoint devices. In this
architecture, Dell PowerEdge servers and Dell Wyse thin clients provide the fast CPU, I/O, and
rendering speeds to support efficient VDI and Unified Communications services.
Implementing a successful virtualized UC initiative requires a comprehensive and proven
architecture. Dell products and infrastructure services are designed to help deploy a cost-effective,
reliable, and responsive solution while:
● Lowering complexity and getting the VDI environment deployed quickly, with less risk.
● Centralizing management and efficiently distributing virtual and collaborative service
workloads across the datacenter.
● Improving application continuity and meeting service-level agreements (SLAs)
Powered by Intel® Xeon® processors, the latest generation of high-speed Dell PowerEdge™ R720
servers maximizes performance, providing fast processing speeds, large memory capacities, and
flexible I/O. Dell Force10 high-performance Ethernet switch/routers provide industry-leading density
and resiliency to simplify network delivery at low cost. All of these industry-standard technologies
come together in compact building blocks that help to simplify desktop virtualization and unified
communications service deployments.
3
3.1
Hardware Components
Dell PowerEdge R720 Servers
For purposes of architecture testing, the design incorporates best-in-class Dell Generation 12 server
platforms —Dell PowerEdge R720 servers. These dual-socket platforms run the fastest Intel Xeon E52600 family of processors, host up to 768GB RAM, and support up to 16 2.5” SAS disks or 12 3.5” SAS
disks, providing uncompromising performance and scalability in a compact 2U form factor.
In this test configuration, there were three Dell PowerEdge R720 servers used: one to host virtual
machines (VMs) for the infrastructure, one to host VMs for Microsoft® Lync® server components, and
one to host virtual desktops. All three servers had similar configurations as outlined below.
Configuration of Dell PowerEdge R720 Servers
2 x Intel Xeon E5-2640 Processor (2.5 GHz, 6 cores/12 threads
per CPU)
64GB Memory (4 x 16GB DIMMs @ 1600Mhz)
Microsoft Windows Server 2008R2 Enterprise with Hyper-V
6 x 146GB SAS 6Gbps 15k Disks
PERC H710 Mini Integrated 1GB RAID Controller
Broadcom 5720 1Gb QP NDC (LAN)
Broadcom 5720 1Gb DP NIC (LAN)
iDRAC7 Enterprise w/ vFlash, 8GB SD
2 x 750W PSUs
For more information on the Dell PowerEdge R720 servers (and other server offerings from Dell),
please visit: LINK
3.1.1
Local Storage
The servers relied on local storage to store operating system images and virtual machines for the
infrastructure servers, Microsoft® Lync® servers, and the Citrix XenDesktop virtual desktops. On each
server, the configuration of local storage was as follows:
● Two 146GB SAS 6Gbps 15k disks were configured as RAID 1 volumes to host Windows Server
2008 with Hyper-V.
● The remaining four 146GB SAS 6Gbps 15k disks were configured as RAID 10 volumes to store
the VMs.
3.2
Dell Wyse Endpoints
Citrix XenDesktop can deliver virtual desktops to a variety of endpoint device types. Dell Wyse offers a
wide selection of secure, reliable, and cost-effective thin and cloud clients that integrate easily into any
virtualized infrastructure while meeting budget and performance requirements. The test environment
used several different models of Dell Wyse cloud client devices, specifically Wyse R class (Wyse R10L
and R00LX), Wyse Z class (Wyse Z50D and Z90D7), and the Wyse D class (Wyse D90D7) clients. For
more information on all Dell Wyse client devices, please visit: LINK
3.2.1
Dell Wyse R Class Cloud Clients
Wyse® R class™ cloud clients contain powerful processors, dual monitor support, fast graphics, and a
multiple USB ports for peripheral support. To support the demands of multimedia applications, these
clients incorporate the advanced ATI 690E chipset from AMD. They typically use between 12 and 15
watts of power, compared to a PC that typically uses 70 to 150 watts. These clients use the Dell Wyse
ThinOS, a thin client operating system. For more information on Dell Wyse R Class client devices,
please visit: LINK.
3.2.2
Dell Wyse Z Class Clients
The Wyse® Z class™ clients have an efficient processor and a silent, fanless design that conserves
power usage and emissions. AMD G-Series Accelerated Processing Units create an ideal VDI platform
for Unified Communications services. These client devices deliver excellent performance for HD
multimedia graphics, voice, and video applications, and support hardware-accelerated DirectX® 11
graphics with OpenGL 4.0 and OpenCL support. For more information on Dell Wyse Z Class client
devices, please visit: LINK.
The Wyse Z90D7 is a high-performance and Windows Embedded Standard 7 thin client for virtual
desktop environments. Featuring a dual-core AMD processor, its revolutionary design eliminates
performance constraints, allowing it to achieve incredible speed and power for demanding
multimedia applications and HD video.
The Wyse Z50D is designed for power users, and is for demanding multimedia applications. It
combines an embedded Wyse-enhanced SUSE Linux Enterprise with a dual-core AMD 1.6 GHz
processor and a revolutionary graphics engine to accelerate 2D/3D graphics and HD video.
3.2.3
Dell Wyse D Class Thin Clients
Running Windows Embedded Standard 2009, the Dell Wyse D90D7 client is a high-performance thin
client for virtual desktop environments. Featuring a unified engine that eliminates performance
constraints, this client achieves outstanding speed and power for demanding VDI and embedded
Windows applications, rich graphics, and HD video. Driving the high speed and performance is a
powerful energy-saving AMD G Series dual core 1.4GHz processor, creating a solid platform to support
a range of applications. For more information on Dell Wyse D Class client devices, please visit: LINK.
3.3
Force10 S55 Network Switch
In this architecture, all servers share a single Force10 S55 switch for network connections. As user
density increases, adding another Force10 S55 switch is recommended to add redundancy.
Model
Force10
S55
Features
44 x BaseT
(10/100/10
00) + 4 x SFP
Options
Redundant PSUs
4 x 1Gb SFP ports the support copper or fiber
12Gb or 24Gb stacking (up to 8 switches)
2 x modular slots for 10Gb uplinks or stacking modules
Uses
Top of Rack (ToR)
switch for LAN
Public and
Management
Networks
The diagram below shows features on the front and back of the Force 10 S55 switch.
An optimal design uses the 10Gb uplink modules, creating 10Gb uplinks to a core or distribution
switch. If 10Gb to a core or distribution switch is unavailable, the front 4 x 1Gb SFP ports can be used.
The front 4 SFP ports can support copper cabling and can be upgraded to optical fiber to support
longer distances. For more information on the Dell Force10 S55 switch, please visit: LINK
3.4
Network Topology
As shown below, the network topology defines a management network as well as the network that
supports VDI traffic between the servers and the thin clients.
4
4.1
Software Components
Overview
The software technologies in this architecture deliver a rich multimedia experience for collaborative
applications in a VDI environment. The software components include:
● Microsoft Windows Server® 2008 R2 SP1 with Hyper-V role
● Microsoft Windows Server® 2012 with Hyper-V role
● Microsoft® System Center 2012 Virtual Machine Manager (SCVMM)
● Microsoft® Lync® Server 2010
● Citrix XenDesktop 5.6 FP1 (feature pack)
● Citrix HDX RealTime Optimization Pack 1.2 for Microsoft® Lync®
This section introduces the general functionality of each component and discusses configuration
settings within Citrix XenDesktop relative to the reference architecture for Microsoft® Lync®.
Microsoft Windows Server® 2008 R2 SP1 and 2012 with
Hyper-V® and Microsoft® SCVMM
4.2
On two physical servers, Microsoft Windows Server® 2012 Datacenter Edition was configured with
Hyper-V® to host VMs for infrastructure and Microsoft® Lync® software services. All virtual servers on
these physical machines were installed with Microsoft Windows Server® 2008 R2 SP1.
The third physical server was installed with Microsoft® Windows® 2008 R2 SP1 to host virtual
desktops. Citrix XenDesktop can be hosted bare metal or on a choice of hypervisors (Citrix XenServer,
VMware ESXi, or Microsoft Hyper-V®). For this architecture, Citrix XenDesktop was deployed on
Microsoft Server® 2008 R2 SP1 with Hyper-V®. Best practices were applied by leveraging the
Hyper-V® Best Practice Analyzer as noted in MS KB77238. Citrix XenDesktop was configured to host
Microsoft Windows® 7 SP1 for all virtual desktops.
Microsoft System Center 2012 Virtual Machine Manager (SCVMM) was used to manage the
environment.
4.3
Microsoft® Lync® Server 2010
Microsoft® Lync® Server 2010 gives users a single interface for a variety of communications tools:
voice, IM, and audio, video, and Web conferencing. It tracks presence information, such as user
pictures, skills, and locations, giving users the context they need for communications. The same
presence and contact information can be used across both Microsoft® Lync® 2010 and Microsoft
Office® applications. Users can collaborate more effectively using desktop and application sharing,
Microsoft PowerPoint® uploads, and rich whiteboarding.
Microsoft offers several licensing options to scale as required for each site’s Unified Communications
needs. A Microsoft® Lync® Server 2010 license is required for each operating system environment
running a server instance and there are two edition types:
● Microsoft® Lync® Server 2010 Standard Edition: Standard Edition supports IM, presence,
conferencing, and an option for voice. It requires a single system to host the server components
and database for storing user and conferencing information.
● Microsoft® Lync® Server 2010 Enterprise Edition: Enterprise Edition supports more
sophisticated conferencing capabilities, and enables separation of server functionality and data
storage to achieve higher densities and load balancing for better availability. Enterprise Edition
was used in the testing of this reference architecture.
A Client Access License (CAL) is also required for each user or device accessing the Microsoft® Lync®
Server. (For more information on licensing Microsoft® Lync® 2010, see http://lync.microsoft.com/enin/HowToBuy/Pages/pricing-licensing.aspx.)
Microsoft® Lync® requires the following logical servers:
● A domain controller, installed with Active Directory Domain Services (AD DS), Active Directory
Certificate Services (AD CS), and DNS Server roles.
● A Microsoft® Lync® Front End Server installed with Microsoft® Lync® Server 2010 Enterprise
Edition. Front end services include Session Initiation Protocol (SIP) Registrar, SIP proxy,
conferencing and other services such as A/V conferencing, Web conferencing, instant messaging,
application sharing, response group, bandwidth policy, call park, conferencing announcement,
and audio test.
● A Microsoft SQL Server® Back End Server, installed with Microsoft SQL Server® 2008 SP1. The
Back End Server provides database services for the Front End pool.
● The Microsoft® Lync® FileShare Server, for storing files for the Microsoft® Lync® Server.
● A Monitoring/Archiving Server, installed with Microsoft® Lync® Server 2010 Enterprise Edition
and Microsoft SQL Server® 2008 SP1.
Figure 2 shows virtual servers for Microsoft® Lync® services (as well as SCVMM, SQL, and other
infrastructure services) hosted on two physical machines. Addresses are also shown for one of the two
networks.
Figure 2. Two physical machines host Microsoft® Lync® and other infrastructure and
management services.
4.4
Citrix XenDesktop
Citrix XenDesktop is a desktop virtualization solution that delivers individual applications or complete
hosted desktops to users across the entire enterprise. It combines the benefits of centralized
management and security with a personalized user experience. Key features include:
● Personal vDisk. Citrix XenDesktop 5.6 gives IT the ability to deliver personal VDI desktops
through innovative “Personal vDisk” technology that enhances personalization and reduces
storage costs. This feature centrally stores a single copy of Microsoft Windows® and combines it
with a personal vDisk for each user’s apps, data, and settings, simplifying enterprise-wide
deployment of virtual desktops.
● High definition user experience (HDX) technology. XenDesktop 5.6 contains significant
enhancements to HDX technology, delivering virtual desktops over WANs to mobile workers and
branch office employees up to three times faster than previous releases. Key enhancements
include faster printing and scanning, faster app launch, and flexible Quality of Service (QoS)
controls to optimize the user experience. XenDesktop 5.6 also features significant multimedia,
voice and video enhancements, including new Flash redirection technology that enhances video
and audio performance over WANs.
● Broad device support. Using Citrix XenDesktop 5.6, customers can deliver self-service
applications and desktops to more than one billion devices, including PCs, Macs, tablets,
smartphones, and thin clients — and all major device operating platforms, including Apple iOS,
Google Android, and Google ChromeOS. XenDesktop 5.6 enables a rich, native experience on
each device, including support for gestures and multi-touch features, customizing the experience
based on the type of device and leveraging device features to optimize performance.
● Support for Microsoft RemoteFX. XenDesktop with HDX and RemoteFX (a key capability of
Microsoft Hyper-V®) delivers a great user experience for rich content, regardless of whether
execution occurs on the server or client device.
A pooled VDI desktop model was used in this architecture to deploy desktop images to the Dell Wyse
thin clients. Pooled VDI desktops use a single OS image to create multiple thinly provisioned or
streamed desktops. In this test scenario, pooled desktops were thinly provisioned from a single OS
image and streaming was not used. Using hypervisor APIs, Machine Creation Services (MCS) in
XenDesktop were used to deliver desktop images and to create, start, stop, and delete virtual
machines.
Citrix XenDesktop 5.6 Feature Pack 1 supports the optional use of Personal vDisks. A pooled VDI
desktop can use a Personal vDisk to maintain application, profile and data differences that are not part
of the base image. This creates a persistent “personal” desktop, reducing the need for independent and
dedicated desktops in the enterprise. For the purpose of testing this Microsoft® Lync® architecture,
Personal vDisks were not configured.
Supporting Remote PC FlexCast delivery, Citrix XenDesktop 5.6 Feature Pack 1 includes
enhancements to Citrix Receiver and HDX technologies to take advantage of local endpoint rendering
where possible. To support the Citrix HDX RealTime Optimization Pack 1.2, Citrix XenDesktop 5.6
Feature Pack 1 is required.
4.5
Citrix ICA Protocol and HDX
For less-intensive application workloads, the native Citrix ICA and HDX optimizations make desktop
virtualization scalable and practical, even over low bandwidth and high latency WAN connections.
HDX technology includes these features that help to optimize performance and provide a rich highdefinition user experience:
● MultiStream ICA Protocol splits virtual desktop traffic into 5 streams — real time, interactive,
background, bulk and RTP Voice — to enable network administrators to prioritize traffic by type
and maintain QoS. RTP Voice delivers optimal audio performance, even over high latency
networks. Adaptive compression and de-duplication algorithms optimize for network efficiency.
● Seamless isochronous plug-and-play provides support for webcams and USB audio devices.
● Client-side webcam video compression, where possible, reduces bandwidth requirements.
● Voice over IP SDK supports leading telepresence applications. The optimization offloads voice
traffic from virtual desktops and processes the voice stream locally using advanced voice
routing.
● Peer-to-peer connections enable enterprise-scale video conferencing.
For more info on HDX, see http://www.citrix.com/products/xendesktop/features/high-defexperience.html
Citrix HDX RealTime Optimization Pack 1.2 for
Microsoft® Lync®
4.6
Citrix HDX RealTime Optimization Pack 1.2 supports features that enable a highly scalable solution for
delivering real-time audio-video conferencing and USB or VoIP enterprise telephony using Microsoft®
Lync® in Citrix XenDesktop, XenApp, and VDI-in-a-Box environments. Users can participate in audiovideo or audio-only calls to and from other HDX RealTime users and other standards-based video
desktop and conference room systems.
The installation files for the Optimization Pack are available for download via the XenDesktop 5.6
Feature Pack 1, which is available from http://www.citrix.com/downloads.
The Optimization Pack contains both client and server components:
● The client component, called Citrix HDX RealTime Media Engine, is integrated with the Citrix
Receiver on the endpoint device and performs all signalling and media processing directly on
the user device itself, offloading the server for maximum scalability, minimizing network
bandwidth consumption, and ensuring optimal audio-video quality.
● The server-side (i.e., virtual desktop) component, Citrix HDX RealTime Connector, is a connector
to the Microsoft® Lync® client that drives the RealTime Media Engine on the endpoint. The
Connector runs in the virtual server environment alongside Microsoft® Lync® client and
communicates signalling information over a Citrix ICA virtual channel to the RealTime Media
Engine running on the user device.
4.6.1
How the Optimization Pack Works
To understand how the architecture works when the Optimization Pack is used, picture a typical
softphone architecture, as illustrated below. At the top, a UI layer allows users to make and answer
calls. There is some business logic in the middle, and a media engine at the bottom that handles the
audio-video encoding/decoding and Session Initiation Protocol (SIP) signalling.
User Interface
Business Logic
Media Engine
By pulling the media engine out from this architecture and moving it over to the user device, the
workload of media processing also moves to the user device. In such an optimized architecture, the
communications between the media engine and the layer of software above it, which would normally
happen on the same machine, now take place over a virtual channel. This inter-process
communication, however, consists only of orchestration commands (e.g., “Make a call”). The actual
media traffic flows directly from the media engine on the user device to the other party on the call (or
to a conferencing bridge in the case of a multi-party call). As a result, there is no media processing
happening on the server, only on the user device.
Server Side (Virtual Desktop)
User Interface
Business Logic
User Device
Media Engine
Virtual
When the Citrix HDX RealTime Optimization Pack 1.2 is configured, it changes where processing
occurs and how data is routed between solution components. The next sections illustrate how the
Optimization Pack reroutes media data from user device to user device, moving processing of media
data off of the server that hosts the virtual desktops.
4.6.2
Data Flow with the Optimization Pack
Provided as part of the Optimization Pack, the RealTime Media Engine is installed on each thin client.
When a user opens the Microsoft® Lync® client in a virtual desktop, the RealTime Media Engine on the
user device is initialized and registers with the Microsoft® Lync® server. Session Initiation Protocol
(SIP) is used to place and initialize the call session, and only signalling information is sent over the ICA
protocol to the XenDesktop server (Steps 1-4 in Figure 3). After the call session is established, all
media traffic flows directly peer-to-peer (from one user endpoint directly to the other, as shown in
Step 5 in Figure 3). In the case of a multi-party call, media traffic is routed directly to the Microsoft®
Lync® Audio-Video Conferencing Server.
Figure 3. Data Flow with Citrix HDX RealTime Optimization Pack 1.2.
The RealTime Media Engine running on the endpoint device transmits compressed video directly from
the endpoint and avoids sending uncompressed video over the network. This reduces network load as
well as decreases processing on the virtual desktop server. In this way the Optimization Pack makes
the solution work well even in WAN environments and allows LAN-based deployments to scale. In
addition, the RealTime Media Engine performs decompression on the endpoint and not in the Citrix
server, which helps to significantly increase VDI scalability.
Of course, for optimal performance, the thin clients should feature codecs that accelerate compression
and decompression operations on the endpoints. Citrix has validated the Optimization Pack for
Microsoft® Lync® on a number of Dell Wyse thin client devices. To see the list of validated devices, see
http://support.citrix.com/proddocs/topic/hdx-realtime-optimization-pack-12/hdx-realtimeoptimization-pack-12-system-requirements.html.
As Figure 3 illustrates, the media traffic does not go through the Citrix XenDesktop server at all. The
RealTime Media Engine routes audio/video directly between clients over UDP and bypasses TCP-
based VDI protocols entirely, thereby allowing voice and video traffic to flow with minimal latency
and no delay spikes.
4.6.3
Without the Optimization Pack
Figure 4 illustrates the media data flow when the Optimization Pack is not used. When the user opens
Microsoft® Lync® in the virtual desktop, the user registers with the Microsoft® Lync® server. Similar to
when the Optimization Pack is used, Session Initiation Protocol (SIP) is used to place and initialize the
call session. Signalling information is again sent over the ICA protocol to the virtual desktops on the
Citrix XenDesktop server. Once the call is established, however, media traffic continues to flow
through the virtual desktop, with every inbound and outbound packet passing through the VDI
Hyper-V host.
Figure 4. Data Flow with no Optimization Pack.
Because all audio/video traffic is flowing over ICA (from endpoint1 to Virtual Desktop1 to Virtual
Desktop2 to endpoint2, as shown in Step 4 in Figure 4), additional latency is introduced. In addition,
all compression and decompression operations occur on the virtual desktops and not in the endpoints,
resulting in a significant CPU impact on the VDI Hyper-V® host. The collected test metrics in the next
section demonstrate the performance tradeoffs that occur without the use of the Optimization Pack.
5
5.1
Test Description, Methodology, and Results
Overview
To simulate the desktop experience of a VDI environment with a Microsoft® Lync® 2010 workload,
Citrix and Dell engineers configured a small test environment. The goal was to assess VDI user
experience and analyze performance of Microsoft® Lync® audio and video conferencing applications
running within virtual desktops with and without the Optimization Pack.
Two test scenarios were created:
● Test case #1 simulated shared audio, establishing three separate audio conferences
● Test case #2 simulated shared video, supporting two separate video conferences
With each test scenario, engineers conducted multiple test runs: first using Citrix XenDesktop without
the Optimization Pack, and then again using Citrix XenDesktop with the Optimization Pack. The intent
was to understand the impact of the Optimization Pack on VDI user densities with Microsoft® Lync®
2010 workloads.
5.2
Test Configuration
As shown back in Figure 1 (page 5), three Dell PowerEdge R720 servers were configured with the
following virtual machines on Microsoft Server 2008 with Hyper-V:
● Citrix XenDesktop VDI Server:
―
10 x Windows 7 VMs (no Optimization Pack)
―
10 x Windows 7 VMs with Optimization Pack 1.2
● Infrastructure Server:
―
Domain Controller (DC1)
―
XenDesktop Controller (DDC1)
―
System Center Virtual Machine Manager (VMM1)
―
SQL Database used for SCVMM and XenDesktop (SQL1)
● Microsoft® Lync® Server:
―
Microsoft® Lync® Front-End Server (LYNCFE)
―
Microsoft® Lync® Back-End Server (LYNCBE)
―
Microsoft® Lync® File Server (LYNCFS)
―
Microsoft® Lync® Monitoring and Archiving Server (LYNCMA)
5.2.1
Configuration Details
Engineers performed the following procedures to configure the Dell PowerEdge R720 servers and
create the test environment:
● Installing the Microsoft Windows Server® OS (Microsoft Windows Server® 2008 R2 SP1 was
installed on the compute host while Microsoft Windows Server® 2012 was installed on the two
infrastructure servers)
● Configuring the Hyper-V® hypervisor on the three compute and infrastructure servers
● Creating the required infrastructure VMs
● Setting up the infrastructure Domain Controller
● Setting up the infrastructure Microsoft SQL® servers
● Setting up the Microsoft SCVMM 2012 server
● Setting up the Citrix XenDesktop 5.6 FP1 server
● Setting up the Microsoft® Lync® infrastructure
● Creating the target VDI VMs with Microsoft Windows® 7 x86 installed on them
● Setting up the Citrix HDX RealTime Optimization Pack for Microsoft® Lync® on both the server
and on the Dell Wyse thin client devices
Citrix has previously validated the Optimization Pack for Microsoft® Lync® on a number of thin client
devices. To see the list, visit http://support.citrix.com/proddocs/topic/hdx-realtime-optimizationpack-12/hdx-realtime-optimization-pack-12-system-requirements.html.
5.2.1.1
Infrastructure and Desktop VM Configuration
The table below summarizes configuration parameters for the various infrastructure Microsoft®
Lync® VMs.
VM Name
Processor
RAM
DC1
2 vCPUs
2 GB
VMM1
4 vCPUs
4 GB
DDC1
4 vCPUs
4 GB
SQL1
4 vCPUs
8 GB
LyncFE
4 vCPUs
4 GB
LyncMA
4 vCPUs
4 GB
LyncFS
4 vCPUs
4 GB
LyncBE
4 vCPUs
8 GB
The table below summarizes configuration parameters used to configure target virtual desktops for
the XenDesktop pools. One pool contains 10 VMs that are installed with the Optimization Pack; the
other pool contains 10 VMs without the Optimization Pack.
5.3
Configuration Parameter
XenDesktop Setting
CPU resource
1 vCPU
Memory
Dynamic Memory: 1024MB-2048MB
Write Cache
2GB (Fixed)
Desktops Configured
10 with Optimization Pack; 10 without Optimization Pack
Test procedures
The testing was largely a manual process. For each test run of either a voice or video conferencing
workload, test engineers performed this sequence of steps:
1) Logging into each thin client and connected to its desktop VM.
2) Starting a script to collect performance metrics (using perfmon) at the hypervisor level. (Due to
time limitations, data was not collected at the thin client endpoints.)
3) Manually initiating the Microsoft® Lync® voice or video connection.
4) Simulating the conferencing workload. (An MP3 player or tablet played an audio or video stream
to simulate a voice or video source.)
5) Stopping the Lync session and stopping the performance monitoring.
6) Logging off the desktop VM.
7) Analyzing the collected data and graphing the performance results.
5.4
Test Results and Data Analysis
The tests compared performance of voice and video conferencing workloads on thin clients running
virtual desktops. Performance data was collected for the desktops configured with and without the
Citrix HDX RealTime Optimization Pack for Microsoft® Lync®. Results and analysis are presented in
the following pages.
5.4.1
Data Analysis: Audio Conferencing Workload
The test simulated three audio conferences occurring concurrently between three pairs of users, each
using one of the six virtual desktops running on a thin client device. Network bandwidth, logical
processor utilization, memory utilization, and disk I/O datapoints were collected for each of the
virtual desktops as well as the Hyper-V host.
5.4.1.1
Audio – Without Optimization Pack
The following graphs show network bandwidth, logical processor utilization, and memory utilization
recorded under an audio conferencing workload using six virtual desktops without the Citrix HDX
RealTime Optimization Pack for Microsoft® Lync®. Disk I/O metrics are not included because disk I/O
was not impacted. In the data below, the audio conference sessions started at minute 3:00 and
stopped at minute 8:00. Please note that in the test scenario, a total of eight virtual desktops were in a
running state on the host although only six participated in audio conferencing.
Network Bandwidth
The graph below shows the cumulative network bandwidth utilization for the six virtual desktops
measured at the Hyper-V host network adapter. The six VMs consumed approximately 150,000 bytes,
using an average total network bandwidth of approximately 1171 kbps (195 kbps per VM).
Logical Processor Utilization
The graph below shows the aggregate logical processor utilization consumed by the six virtual
desktops. It shows the %Guest Runtime on the Hyper-V® server. The %Guest Runtime is the average
percentage of time the guest code is running across all logical processors.
Prior to the start of the audio conferences, utilization was approximately 1% and increased to 8% at
peak, indicating that the six virtual desktops consumed approximately 7% (or about 1.17% per VM) of
the available logical processing power during the audio calls. Thus, a single server can support a
theoretical maximum of approximately 84 VMs running voice calls.
Memory Utilization
Dynamic memory was configured for the Hyper-V® VMs. Each VM started at 1 GB of RAM and
dynamically grew to a maximum of 2 GB. The graph below shows that memory utilization did not
impact the performance results. With eight virtual desktops running, memory consumption of the
desktops consisted of approximately 8GB, resulting in a total memory consumption of about 10 GB
including the parent partition.
Total Memory (GBytes)
Memory Utilization
5.4.1.2
64
56
48
40
32
24
16
8
0
Audio – With Optimization Pack
The following graphs show network bandwidth, logical processor utilization, and memory utilization
recorded under an audio conferencing workload using six virtual desktops with the Citrix HDX
RealTime Optimization Pack for Microsoft® Lync®. Metrics for disk I/O are not included because disk
I/O was not impacted. In the data below, the audio conferencing sessions started at minute 5:00 and
stopped at minute 10:00. Please note that in this scenario, a total of 16 virtual desktops were in a
running state on the host (twice the number as in the previous scenario).
Network Bandwidth
The graph below shows the cumulative network bandwidth utilization for the six virtual desktops
measured at the Hyper-V® host network adapter. In the graph below, there are a few network spikes
due to changes on the screen requiring redraws. The overall network utilization is close to zero.
Logical Processor Utilization
The graph below shows the aggregate logical processor utilization consumed by the six virtual
desktops. It shows the %Guest Runtime on the Hyper-V® server. The %Guest Runtime is the average
percentage of time the guest code is running across all logical processors.
Prior to the start of the audio conferences, utilization was about 2%. This is twice that of the previous
scenario (which saw about 1% utilization) because there were double the number of machines
running. With the Optimization Pack, utilization during the conferences fluctuated but the average
remained around 2-3%. This is largely below the 8% utilization level that was consistently observed
in the previous test run without the Optimization Pack.
Memory Utilization
The graph below shows that memory utilization did not impact the performance results. The 16
running virtual desktops consumed about 16 GB, resulting in a total memory consumption of about 20
GB including the parent partition.
Total Memory (GBytes)
Memory Utilization
5.4.2
64
56
48
40
32
24
16
8
0
Data Analysis: Video Conferencing Workload
The test simulated two video conferences occurring concurrently between two pairs of users, each
using one of four virtual desktops running on a thin client device. Data was collected for each of the
virtual desktops at the Hyper-V® level. All of the virtual desktop sessions were connected at a
resolution of 1680x1050.
5.4.2.1
Video – Without Optimization Pack
The following graphs show network bandwidth, logical processor utilization, and memory utilization
recorded under the video conferencing workload using four virtual desktops without the Citrix HDX
RealTime Optimization Pack for Microsoft® Lync®. In the data below, the video conferencing sessions
started at minute 7:00 and stopped at minute 12:00. Please note that in this scenario a total of eight
virtual desktops were in a running state on the host.
Network Bandwidth
The graph below shows the cumulative network bandwidth utilization for the four virtual desktops
measured at the Hyper-V® host network adapter. The 4 VMs consumed approximately 550,000 bytes,
using an average total network bandwidth of about 4300 kbps (1074 kbps per VM).
Logical Processor Utilization
The graph below shows the aggregate logical processor utilization for the four virtual desktops. It
shows overall processor utilization of the Hyper-V® server of 12% (3% utilization per VM). Thus, a
single server can support a theoretical maximum of approximately 33 VMs running video conferences.
Memory Utilization
The graph below shows that memory utilization did not impact the performance results. The eight
running virtual desktops consumed approximately 8 GB, resulting in a total memory consumption of
about 10-12 GB including the parent partition.
Total Memory (GBytes)
Memory Utilization
5.4.2.2
64
56
48
40
32
24
16
8
0
Video – With Optimization Pack
The following graphs show network bandwidth, logical processor utilization, and memory utilization
recorded under the video conferencing workload using four virtual desktops with the Citrix HDX
RealTime Optimization Pack for Microsoft® Lync®. In the data below, the video sessions started at
minute 5:45 and stopped at minute 11:00. Please note that in this scenario, a total of 16 Virtual
desktops were in a running state on the host (twice the number as in the previous scenario).
Network Bandwidth
The graph below shows the cumulative network bandwidth utilization for the four virtual desktops
measured at the Hyper-V® host network adapter. In the graph below we can see few network spikes
due to changes on the screen requiring redraws. The overall network utilization is close to zero.
Logical Processor Utilization
The graph below shows the aggregate logical processor utilization for the four virtual desktops. It
shows the overall processor utilization of the Hyper-V® server.
Memory Utilization
The graph below shows that memory utilization did not impact the performance results. The 16
running virtual desktops consumed approximately 16 GB, resulting in a total memory consumption of
about 20 GB including the parent partition.
Total Memory (GBytes)
Memory Utilization
64
56
48
40
32
24
16
8
0
6
Conclusion
As shown in the collected performance metrics, using the Citrix HDX RealTime Optimization Pack for
Microsoft® Lync® decreased the processing load on the virtual desktops and the amount of network
bandwidth consumed. The Optimization Pack allows the solution to take advantage of the capabilities
of the Dell Wyse thin clients and scale collaborative services more effectively.
References
For more information, see the following resources:
● Dell PowerEdge servers, http://www.dell.com/us/enterprise/p/poweredge-r720/pd
● Dell Wyse thin clients, http://www.dell.com/us/business/p/wyse-xenith-class/pd
● Citrix XenDesktop, http://www.citrix.com/products/xendesktop/overview.html?ntref=prod_cat
● Citrix HDX RealTime Optimization Pack for Microsoft® Lync®,
http://support.citrix.com/proddocs/topic/technologies/hdx-realtime-optimization-packwrapper.htm
● Microsoft® Lync®, http://lync.microsoft.com
Documentation:
● Wyse® Enhanced Microsoft® Windows® Embedded Standard 7 WFR2 Administrators Guide
● A Sizing Study of Microsoft® Lync® Server 2010 and its Back End SQL Database on Dell™
PowerEdge™ Servers
About the Authors
Loay Shbeilat is a Solutions Architect for Worldwide Alliances with Citrix. Loay has over 13 years of
experience and expertise on the broader Microsoft and Citrix solutions software stack, as well as in
enterprise virtualization, storage, networking, and enterprise data center design.
Senthil Baladhandayutham is the Solutions Development Manager in the Desktop Virtualization
Solutions Group at Dell, managing the development and delivery of enterprise-class desktop
virtualization solutions based on Dell data center components and core virtualization platforms.
Gus Chavira is a Principle Solution Architect in the Desktop Virtualization Solutions Group at Dell in
charge of building Reference Architecture. Solution direction, testing, planning are all responsibilities
of the S.A. In addition to this responsibility, Gus has over 20 years working in Virtualization and
related fields.
Neetu Arora is a Lead Solution Engineer in the Desktop Virtualization Solutions Group at Dell building,
testing, validating, and optimizing enterprise VDI stacks. In addition to this responsibility, Neetu has
10 years of experience working in Virtualization and related fields.
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