MICROSOFT

Remote Desktop Protocol

Performance Improvements in Windows Server 2008 R2 and Windows 7

Microsoft Corporation

January 2010

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Microsoft, Aero, ClearType, Internet Explorer, PowerPoint, Silverlight, Windows, Windows Media,

Windows Server, and Windows Vista are trademarks of the Microsoft group of companies. All other

trademarks are property of their respective owners.

Contents Copyright ....................................................................................................................................................... 2

Contents ........................................................................................................................................................ 3

Overview ....................................................................................................................................................... 4

User Scenarios ............................................................................................................................................... 5

Test Setup ..................................................................................................................................................... 6

Remote Desktop Connection Settings ...................................................................................................... 6

Presentation Virtualization ........................................................................................................................... 8

Color Depth ............................................................................................................................................... 8

ClearType Virtualization (a.k.a. Font Smoothing) ................................................................................... 10

Desktop Composition .............................................................................................................................. 11

Embedded Multi-Media Performance .................................................................................................... 12

Multi-Media Redirection ......................................................................................................................... 14

Effects of Latency on Broadband Remoting Performance ...................................................................... 15

Conclusion ................................................................................................................................................... 16

Appendices .................................................................................................................................................. 17

Appendix A. Hardware Configuration ..................................................................................................... 17

Appendix B. Understanding Network Traffic Profiles ............................................................................. 18

Overview With the release of the Windows Server®°2008 R2 and Windows®°7 operating systems, Remote Desktop

Protocol (RDP) is more feature rich, enabling new presentation and remote-oriented functionality such

as accelerated bitmap rendering, multi-media redirection streaming, and network topology awareness.

In short, RDP is better able to support today’s ever increasingly complex and rich multi-media

environment.

As these features become integrated in the enterprise environment, it is important to analyze and

understand their impact on your current network infrastructure and the end-user experience. This paper

details different RDP features and the potential improvements to usability and quality of the end user

remoting experience as well as system deployment metrics. It also includes performance considerations

for individual features that can help guide your decisions when modifying your deployment

configuration to improve performance or tune it to the specific needs of your end users.

To test the impact of different features and compare RDP 7.0 to the previous RDP 6.1 version, we

performed a variety of tests by using automated and simulation tools to demonstrate the user scenarios

outlined in this white paper. These tests are broken down into two broad groups: a set that simulated a

user working with actual Microsoft® Office applications at realistic speeds, and a set of multi-media

scenarios that simulated a rich media environment commonly expected by today’s and tomorrow’s

users. In addition, some of the scenarios have been run at increased network latencies to demonstrate

the viability of using RDP in distributed environments, such as in Branch offices or telecommuting

scenarios where broadband capabilities exist.

Comparisons of previous versions of RDP are covered in previous white papers. However, their results

cannot be directly compared to the results presented in this white paper because the test server/client

hardware as well as networking, the scenarios, and Office applications have all been updated to reflect

current industry expectations. For example, the display sizes used have been updated to reflect higher

desktop resolutions.

User Scenarios Five different user scenarios were used to measure the performance of the Remote Desktop Connection

(RDC) client.

Executive/Complex PowerPoint Scenario. This scenario emulates a user presenting 43 high-

fidelity slides by using Microsoft Office PowerPoint® 2007. The slides contain images,

transitions, and backgrounds with color gradient. The user spends a minimum of 20 seconds

viewing each slide.

Simple PowerPoint Scenario. This scenario emulates a user presenting content by using

PowerPoint 2007. The slides in this scenario are more text-intensive than those in the executive

PowerPoint scenario and have plainer backgrounds and simpler images in the form of black

diagrams.

Typing and Scrolling Scenario. This scenario emulates a user that is using Microsoft Office Word

2007. First the user opens a document and resizes its window and then highlights and changes

the font (to Arial 10 point). Then the user opens a 17-page document (the RDP 5.1 compared to

RDP 6.0 comparison white paper) and then resizes this document two times before starting to

scroll through this document at around 2 pages per minute (at a minimum of 800 milliseconds

per line of text). After completing the scrolling, a new document is opened and 1068 lines of text

consisting of 7059 words is typed into it at a maximum rate of four characters per second, which

equates to an average user typing at 35 words per minute.

Internet Explorer Scenario. This scenario emulates a user browsing the Web by using Windows

Internet Explorer® 8. The user browses and scrolls through multiple Web pages that contain a

mix of text, natural images, and some schematic diagrams. The rate of scrolling is one line every

200 milliseconds, and this Web page takes around ten minutes to scroll through. The Web pages

are stored on the local disk drive of the Remote Desktop Session Host (RD Session Host) server

to avoid errors due to varying load times.

Multi-Media Sample 1. This scenario contains a short variable bit-rate Adobe Flash-encoded

video embedded in a Web page that is stored on the local hard drive of the RD Session Host

server. The video is played within Internet Explorer 8 by an embedded player plug-in. This

scenario emulates users viewing rich content Web pages containing multi-media. The resolution

of the Adobe Flash video is 1152 by 688 pixels.

Multi-Media Sample 2. This scenario contains a short fixed bit-rate Silverlight®-encoded video

embedded in a Web page that is stored on the local hard drive of the RD Session Host server.

The video is played within Internet Explorer 8 by an embedded player plug-in. This scenario

emulates users viewing rich content Web pages containing multi-media. The resolution of the

Silverlight video is 1024 by 576 pixels, its total data rate is 5000 kilobits per second (Kbps), and it

renders at 29 frames per second (fps) with 64 Kbps mono auto.

Multi-Media Sample 3. This scenario contains a thirty-second Windows Media® (WMV)-

encoded video at 29 frames per second at a resolution of 1280 by 720 pixels with a 192 Kbps

audio track. This scenario is used to test multi-media redirection.

Test Setup The tests were conducted in a private lab to avoid external network interference. The results in this

white paper are the average of three to five test runs depending on the standard deviation between the

individual runs. Details of the server and client systems used can be found in the Appendices together

with additional details of how certain measurements were taken, and how they should be interpreted.

Remote Desktop Connection Settings Tests were run by using the following range of Remote Desktop Connection client settings. As the

RDP 6.1 client and RDP 7.0 client vary in their interfaces slightly, both are fully detailed. All test results

indicate the setting combinations used for testing when a one-to-one direct mapping did not exist.

Color depth: High Color (16-bit) and Highest Quality (32-bit)

Connection speed setting on the Experience tab:

a. Windows Vista® with Service Pack 1 client

Default: Modem - 56 kilobits per second (Kbps)

LAN: 10 megabits per second (Mbps) or higher

b. Windows 7 client:

Default: Low-speed broadband - 256 Kbps to 2 Mbps

LAN: 10 Mbps or higher

WAN: 10 Mbps or higher with high latency

Default bulk compression and persistent bitmap caching settings

Font smoothing (ClearType®): On or Off

Desktop composition (Aero®Glass): On or Off

Chart 1 shows all the different client configuration options used in this report and their default settings.

RDP

version

Client

connection

setting

Desktop

background

Font

smoothing

Desktop

composition

Show

contents

while

dragging

Menu and

window

animation

Visual

styles/themes

Persistent

bitmap

caching

6.1 Default

Modem

56 Kbps

6.1 LAN

7.0 Default

Low-speed

broadband

7.0 LAN

7.0 WAN

Chart 1: Client configuration options used in this report and their default settings

Presentation Virtualization

Color Depth In previous versions of RDP, 16-bit color depth always reduced the networking resource requirements of

deployment compared to the 32-bit color depth introduced with Windows Vista in RDP 6.1. In Windows

Server 2008 R2, RDP 7.0 utilizes an improved bitmap compressor so that, for the first time, the higher

fidelity of 32-bit color is obtainable at lower bit rates than 16-bit color for many common scenarios.

Note: The 8-bit color depth is no longer supported in Windows Server 2008 R2 for Remote

Desktop Services. True Color (24-bit) support was retired in Terminal Services in Windows

Server 2008. The only valid options for Windows Server 2008 R2 are High Color (16-bit)

and Highest Quality (32-bit).

Table 1 and Chart 2 compare the total bandwidth (in bytes) consumed by a user scenario that uses

different color-depth settings. The tests were conducted by using the default connection settings (56-

Kbps modem connection setting in RDP 6.1 and the low-speed broadband setting in Windows 7) with

the default bulk compression settings.

Scenario RDP 6.1– 16 bpp

RDP 6.1 – 32 bpp

RDP 7.0 – 16 bpp

RDP 7.0 – 32 bpp

Complex PowerPoint 87507102 87698437 73456182 65661943

Simple PowerPoint 42680431 42600992 36172121 32873438

Word Scroll and Type 2245601 9579862 2846335 6782496

Internet Explorer 8 Scrolling 4017795 15436909 4356808 10991610 Table 1: Color depth comparison for different knowledge worker scenarios

Scenario RDP 6.1 to RDP 7.0 –

16 bpp RDP 6.1 to RDP 7.0 –

32 bpp

Complex PowerPoint -16% -25%

Simple PowerPoint -15% -23%

Word Scroll and Type 27% -29%

Internet Explorer 8 Scrolling 8% -29% Table 2: Network traffic of RDP 7.0 compared to RDP 6.1 by scenario and color bit depth. Less is better.

Chart 2: Color depth comparison for different scenarios

Chart 3: Network traffic of RDP 7.0 compared to RDP 6.1 by scenario and color bit depth. Less is better.

Tables 1 & 2 and Charts 2 & 3 show that RDP 7.0 is more efficient at remoting bitmap-rich content by

reducing between 15% to 29% the total network traffic generated for 32-bit color depth displays. 16-bit

color depth is less effective with reduction in bandwidth for PowerPoint, Web browsing, and Word

scrolling and typing.

ClearType Virtualization (a.k.a. Font Smoothing) ClearType® display technology is a Microsoft font smoothing technique that improves the readability of

text on LCD screens. With the proliferation of LCD screens and the release of Windows°Vista,

Windows 7, and Office 2007, ClearType has become very important. Most of the fonts available in

Windows°Vista and Office 2007 are tuned for ClearType and look unattractive when it is turned off. Due

to these reasons, Remote Desktop Services decided to give the user the option to turn on ClearType.

You can get ClearType in the Remote Desktop Connection (RDC) 7.0 client by going to the Experience

tab and selecting Font smoothing. However, the high fidelity of ClearType comes at a cost.

Normally (with Font smoothing disabled) fonts are transmitted as glyphs. Remote Desktop Protocol

transmits glyphs efficiently and caches them to reduce bandwidth consumption. With ClearType

enabled, fonts are transmitted as bitmaps and not as glyphs; transmitting these bitmaps to the client

results in increased bandwidth consumption. From our initial internal testing, we found that enabling

ClearType for text scrolling and typing scenarios resulted in an increase in bandwidth consumption that

was 79% to 83% greater than when the scenario was run with ClearType disabled (in contrast to RDP 6.1

where enabling ClearType cost between 1x and 2x of extra bandwidth). In RDP 7.0, ClearType can be

enabled in many instances without significant impact in bandwidth compared to RDP 6.1.

Table 3 and Chart 4 show the total bandwidth consumption (in Bytes) for user scenarios running at 16-

and 32-bit color depths with the LAN connection setting + ClearType or Font smoothing explicitly turned

off or on.

RDP version Font smoothing enabled

Font smoothing disabled

Bandwidth increase using font smoothing

RDP 6.1 - 16bpp 5039496 2441593 106%

RDP 6.1 - 32bpp 30295938 9579862 216%

RDP 7.0 - 16bpp 5465492 3059905 79%

RDP 7.0 - 32bpp 12371554 6771320 83%

Table 3: Total bandwidth consumption for ClearType text versus Normal text

Chart 4: Bandwidth consumption for Font smoothing On and Off

Font smoothing is disabled by default on the RDC client, and can be enabled on the Experience tab

either explicitly by selecting the Font smoothing check box or by setting a faster connection type setting

such as LAN or WAN. The RemoteApp Wizard enables font smoothing by default. In Windows

Server°2008 R2, to provide a mechanism to control this setting for all RDP 7.0 remote clients, you can

apply a Group Policy setting to disable font smoothing.

Desktop Composition The Desktop composition feature fundamentally changes the way applications display pixels on the

screen. When Desktop composition is enabled, individual windows no longer draw directly to the screen

or primary display device as they did in earlier versions of Windows. Instead, their drawing is redirected

to off-screen surfaces in video memory, which are then rendered into a desktop image and presented

on the display.

Desktop composition is performed by the Desktop Window Manager (DWM), a new component

introduced in Windows Vista. Through desktop composition, DWM enables visual effects on the desktop

as well as in various features, such as glass window frames, 3-D window transition animations, Windows

Flip, and Windows Flip 3D.

Remote Desktop Protocol was extended to support desktop composition remoting (or, composed mode

RDP). This is achieved by transmitting composition commands from DWM on the server to the RDC

client. The client interprets these commands and renders the desktop. The composition commands can

lead to increased bandwidth consumption, but provide the distinguishable look and feel of the

Windows 7 desktop experience. Multiple features of the Windows 7 desktop took advantage of the

desktop composition technology.

In RDP 7.0, desktop composition has a higher impact on the Word typing and scrolling scenario than on

the PowerPoint scenarios. Desktop composition remoting is only available when connecting from a

Windows Vista computer to another Windows Vista computer or Windows 7 computer, and between a

Windows 7 computer and a server running Windows Server 2008 R2.

Scenario Desktop composition ON Desktop Composition OFF

Complex PowerPoint 66770232 66043451

Simple PowerPoint 35498220 32873438

Word Scroll and Type 12542409 6788096

Table 4: Total server to client network bandwidth used varies by desktop composition

Chart 5: Total server to client network bandwidth used varies by desktop composition

Embedded Multi-Media Performance High fidelity video playback is a new and potentially very taxing scenario for desktop remoting. In a later

section of this report we show a new technology for streaming video to the remote client for local

rendering. In cases where this is not possible, such as for training materials or banner advertisements

embedded in Web-pages, two technologies that are commonly used are Adobe Flash and Microsoft

Silverlight. In this section, we examine RDP performance when remoting such content.

Note: All runs had Remote Desktop Audio Redirection enabled.

For information about the rendering rate calculations used, see Appendix B.

RDP 7 display color depth Flash-IE8 Silverlight-IE8

16 bpp 791425873 895101286

32 bpp 986870751 1148268703

Table 5: Total bytes sent from server to client at default settings

RDP 7 display color depth Flash-IE8 Silverlight-IE8

16 bpp 41.6 46.4

32 bpp 50.2 60.1

Table 6: Bandwidth usage in megabits per second (Mbps) from server to client at default settings

Chart 6: Bandwidth usage from server to client in megabits per second (Mbps) for embedded multi-

media presenting using client default settings

To achieve a better visual update rate, RDP 7.0 is sending more data between the server and client even

though we have already previously noted that it is more efficient at compressing and transmitting

bitmap data than RDP 6.1. The following tables and charts measure the amount of graphical data

rendered at the remote client; this is in effect how much of the remote user’s screen has been updated.

A higher value here indicates a higher visual update rate and thus a much richer and smoother multi-

media user experience.

RDP 7 display color depth Flash-IE8 Silverlight-IE8

16 bpp 9.3 13

32 bpp 11.7 17.3

Table 7: Effective frames per second client rendering rates

Chart 7: Effective frames per second client rendering rates

Multi-Media Redirection Multimedia redirection functionality was introduced with RDP 7.0 and allows using the rendering

capability of the client to play video files. When a client and a server support the same set of codec, the

video file without decompressing is sent to the client for rendering and playing.

In contrast, RDP 6.1 clients always rendered the video files on the server and sent them as a set of

bitmaps to the client to present. The video quality was poor, and is represented in the data set with very

low frame rate (less than 5 frames per second with 400 KB on the wire). The issue with playing back fast-

moving multimedia content in RDP 6.1 was related to the fact that each frame had to be treated as a

distinct bitmap image, and was compressed inefficiently. The original compression format of the image

is a much more efficient compression for the nature of multi-frame video content, and beginning with

RDP 7.0, we are keeping the video in this efficient format as it reaches the bottleneck of the system –

the network. We also don’t waste any additional CPU cycles on the server by decompressing and then

recompressing and encoding the multimedia data to send to the clients.

Display bit depth Avg bandwidth/sec wildlife media FrameRate

16 bpp 1212169 29 fps

32 bpp 1224795 29 fps

Table 8: Average bandwidth and frame rate for media redirection in RDP 7.0

Effects of Latency on Broadband Remoting Performance Both the Branch Office and Telecommuter usage scenarios are affected by limited bandwidth and

increased latencies between the remote users’ client computers and the data center/central computer

facilities they are actually utilizing. For non multi-media applications, such as common knowledge

worker scenarios, the main limitation affecting users is that of medium to higher latency networks,

which might or might not have sufficient bandwidth. As both broadband speed and their availability

increases, higher latency networks will become a more common situation faced by remote desktop

users. Although bandwidth limits are increasing, in many cases round trip latencies are already reaching

their combined network infrastructure switching and speed-of-light limits. For testing these scenarios,

we have assumed sufficient bandwidth exists for the test scenarios and then set the round trip latency

to 100 milliseconds (i.e. 50 msec each way) by using a specialized Wide Area Network (WAN) simulator.

100 msec is typical of coast-to-coast networking delays. We have tested both knowledge worker and

media-rich scenarios.

In many Windows GDI-based knowledge worker applications, the remote server-based application

completes roughly the same amount of drawing onto the remote users’ screen no matter how fast the

network or client system can render the data stream generated. This is contrary to many video encoding

systems that ‘drop’ frames of screen data when the downstream systems (such as network or decoders)

cannot keep up with the expected frame/data rate. If the remoting protocol is unable to efficiently

handle a particular set of network characteristics such as higher latencies, its effective bandwidth usage

will drop; however, as it still renders the same graphical data, the users’ experience will degrade as

graphical data is delivered more slowly than it is actually produced at the remote server. To

demonstrate these effects, we measured the total time an application took to run on the server as well

as how much network data it produced.

Total application time in seconds RDP version, color depth and client connection type setting

Complex PowerPoint – Local no delay

Complex PowerPoint – 100 msec RTT

Extra delay compared to no extra latency

RDP 6.1 – 16 bpp - default 902.6 993.6 10%

RDP 6.1 – 32 bpp - default 899.8 993.5 10%

RDP 6.1 – 16 bpp - LAN 900.7 992.2 10%

RDP 6.1 – 32 bpp - LAN 900.7 994.5 10%

RDP 7.0 – 16 bpp - default 901.4 989.9 10%

RDP 7.0 – 32 bpp - default 901.3 952.4 6%

RDP 7.0 – 16 bpp - WAN 901.9 933.9 4%

RDP 7.0 – 32 bpp - WAN 902.2 925.8 3%

Table 9: Application execution time when using a higher latency network

Chart 8: Extra delay experienced by remote users when running the complex PowerPoint scenario with

WAN simulators

Table 9 shows that RDP 7.0 32 bpp encoding, which reduced bandwidth needs, also helps with higher

latency networks. More importantly, RDP 7.0 has been made more network-aware, and when the user

indicates to RDP that it needs to better handle higher latency links by setting the client connection type

to the WAN setting, RDP 7.0 is able to reduce the negative effects of higher latency on the end-user

experience.

As the bandwidth requirements of the remote scenario increase, so do the benefits of this new RDP 7.0

feature.

Conclusion The test results, and more importantly, the actual end user experience, demonstrate that the

performance of Remote Desktop Protocol 7.0 in Windows Server 2008 R2 and Windows 7 is

substantially better than earlier RDP versions. Highlights include an improved user experience with color

depth and font smoothing, lower network bandwidth usage while being able to tolerate higher latency

network conditions, and redirection of Windows Media, allowing the possibility of full frame rate

remoting of high quality media on LANs on a par with playing multi-media locally.

Appendices

Appendix A. Hardware Configuration

Server: Dual Core AMD 2.4-GHz opteron processor in 1U server with 4 GB of RAM and dual SATA

Disks

Client computer and Network Capture computer: HP5150SFF Single Core AMD64 2.2-GHz

desktop computers with single 80-GB SATA Disks and ATI Graphics

Network switches: Netgear GS108 & FS108-gigabit Ethernet switches

WAN simulator: Intel 3.4-GHz P4HT Desktop with three Intel Pro gigabit PCI network cards

The logical networking layout shown in Diagram 1.

.

Diagram 1: Logical networking layout

Windows

Server 2008

GigaBit Ethernet

Managed Switch

Network

Capture

Machine

Windows

Server 2008

R2

Windows

Vista with

SP1

Windows 7

WAN

Simulator

GigaBit Ethernet

Switch

Dual-Boot Server

Identical Client Machines

Server traffic is

mirrored at

Ethernet frame level

Appendix B. Understanding Network Traffic Profiles

The network monitoring infrastructure records at a small granularity based on a timestamp for each

Ethernet packet received. Over the time a test is executed, we can measure the total amount of

bandwidth consumed by the server to client traffic. In many cases the total bandwidth consumed is

enough to indicate how well a protocol is working compared to a previous version. In some cases

network engineers need to know the average bandwidth consumed per user session over the time the

session is performing useful work. We calculated this based on average mean bandwidth consumed (i.e.

the total bandwidth consumed divided by the total time for the network measurement). The last

important measurement is that of how uniform the network traffic bandwidth distribution is. For this

we used the peak bandwidth consumed over a fixed small time period, in this case a one-second

interval. This peak number can be used to act as additional guidance in provisioning of a network.

Diagram 2: Details of network measurements

Instantaneous Bandwidth Used

Time

Peak BW

Measured over a Small Interval of Time

Average BW Measured Over Total Time

Small Time Interval

Total Measurement Run Time

Total BW used for test

= ∑ of all instantaneous

BW measurements