An upcoming RDP Performance Whitepaper will provide a rich set of data to convince even the most skeptical critics that Windows 7, with its enhanced user experience, performance on the wire, and security outshines Windows XP as the virtualized guest OS of choice.

When users connect to a Windows 7 VM, the RDP7 protocol will be used to communicate between client and VM if RDP 7 or Remote Desktop Connection 7 (RDC7) client is used. RDC7 client is offered on variety of OSs, including XPSP3, Vista SP1 and Vista SP2 and the same client is part of the Windows 7 OS (see blog post for more details: Announcing the availability of Remote Desktop Connection 7.0 for Windows XP SP3, Windows Vista SP1, and Windows Vista SP2 ).

When an RDP 7 client connects to a Windows 7 VM, it can take advantage of all the new features implemented in Windows 7.  However, when the same RDP 7 client connects to a Windows XP VM, it will start talking the 9-year-old RDP 5.2 protocol.

User Experience

To test the user experience improvements that the RDP 7 client provides when connecting to a Windows 7 guest VM, we picked the following scenarios:

1. Media(.wmv) playing in a remote session with Windows Media Player
   1. A Windows 7 VM will give you an experience that is close to watching the same video locally from your PC
   2. On Windows XP with RDP5.x , the video may degrade to become a “slide show” with audio sync behind
2. Video playing from any popular site:
   1. You’ll find that with Windows 7 you can enjoy the video content
   2. With Windows XP, the experience is much worse. You may experience the same “slide show” effect as with media .wmv files
3. Aero graphics (“Aero glass”)
   1. RDP7 with Windows 7 is able to remote Aero for your increased productivity and pleasure, so you don’t need to default to the green field of Windows XP Classic theme.
   2. Windows XP will not be able to provide Aero
4. Audio chat experience
   1. Windows 7 will provide you with bi-directional audio, i.e. with the chance to reply, not only listen silently to the conversation. Using the microphone on your local device, you will be able to change a monologue to a dialogue
   2. With Windows XP, there will be no microphone input from your client computer
5. Multimonitor sessions--here the difference is even more pronounced
   1. If you have more than a single monitor when connected to a Windows 7 VM, all of them will be available to your virtual desktop
   2. If you continue to work with Windows XP, only one of the monitors will be used, all others will sit on your table collecting dust
6. Logon speed
   1. Window 7 Client boots faster; you can initiate logon before the whole OS is booted up.
   2. Windows XP boots slower; you have to wait for the entire OS to boot up before logging on.

Performance

Let’s examine the performance of the RDP 7 protocol compared to the RDP 5.2 protocol of the Windows XP era.

1. Windows 7 introduced a new codec that compresses bitmaps very well and can also distinguish between text and images, applying different compression techniques with different levels of “lossiness” to text or images. The goal with text is to keep it readable, so lossy compression has to be avoided. With images, the human eye is more forgiving when we allow some lossiness, in order to save bandwidth. Windows XP is using RDP 5.2 bitmap compression, which requires twice as much bandwidth on the wire as the RDP 7 codec and does not have a good dynamic approach for different types of content.
2. In addition to the bitmap compression improvement, the RDP 7 protocol supports a better byte compression technique that is 3 times more effective for all content from a VM to an RDP 7 client--graphics, print data, audio, clipboard, media, and so on. A Windows XP VM will use an older byte compression algorithm that will not be comparable to the modern compression technique available in RDP 7.
3. IT admins can prioritize interactive traffic (graphics) higher than non-interactive traffic (print/files/clipboard) by assigning a ratio of available bandwidth to these two categories of traffic. By default in both Windows 7 and Windows XP, 70% of the available bandwidth is given to graphics/interactive data, and 30% to all other content. Only Windows 7 VMs allow admins to control this ratio based on their real needs.

Security

Windows 7 with RDP 7 takes remote session security to the next level. When connecting to a Windows XP VM, a connection will be created before security handshakes are finished:

1. Windows XP VM does not support Kerberos for client/server and/or user authentication
2. Windows XP VM does not support Network Layer Authentication (NLA): the remote session can be created even for a rogue user
3. Windows XP VM, does not support Server Authentication, so this VM can be used by any RDP server to steal user credentials
4. Windows XP VM does not support Transport Layer Security (TLS) / Secure Sockets Layer (SSL)

Windows 7 VM with RDP 7 supports all of the functionality you need to keep your system more secure: user-server authentication, Single Sign On, and Network Layer Authentication.

Administration

Windows 7 VMs are easier to deploy and administrate than Windows XP VMs.

1. On Windows 7, there is no need to install an enlightenment package or to reboot VMs after a VDI configuration. On Windows XP, the administrator needs to install the enlightenment package and reboot the VMs before the OS can be accessed by the user
2. Windows 7 supports offline domain join, which makes the process of joining a VDI VM to a domain faster and less error-prone
3. Windows 7 has a newer version of sysprep, which enables the administrators to create Windows 7 VMs faster

The take-home message from this blog is simple: if you are considering deploying a VDI environment and you're after the best user experience, performance, security, and administration support, I recommend you use a device running the new RDC7 client connecting to Windows 7 as the desktop OS running in the virtual machines.

Source: http://blogs.msdn.com/rds/archive/2009/11/02/windows-7-with-rdp7-best-os-for-vdi.aspx