RDP Client Features

Today's RDP clients (both official and non-official) offer many capabilities. We'll take a look at the various features, although keep in mind that not all of these features are supported on every platform. (We'll talk about the specifics of each platform later in this chapter.)

Also, as you're reading, remember that most of these features can be configured in multiple locations. For example, audio mapping can be enabled or disabled as a property of the Terminal Server's listener port and as a property of the RDP client software. In order to use audio, it must be enabled in both locations. The Appendix of this book has a feature chart that lists every single Terminal Server feature and all the locations at which it can be configured.

Now, let's look at the myriad of features available from RDP client devices.

Local Resource Capabilities

Certain hardware elements of RDP client devices can be configured so that they may be accessed through RDP sessions running on remote Terminal Servers. This process is called "mapping" because it is similar to mapping a network drive or printer port on a server, except that RDP client device mapping occurs in the opposite direction. Mapping local resources involves several steps:

1. When the RDP session is established with the Terminal Server, the client software on the client device sends the server a list of local components that are available to be mapped.

2. If the appropriate mappings have been enabled on the server, the mapping process continues and a dynamic mapping is made to the client device.

3. Part of the RDP protocol, called a "virtual channel" is used for the mapping. One channel is used for each of the different types of device mapping. This channel allows the mapping data to flow back and forth between the RDP client and the Terminal Server.

These mappings are dynamic. They only exist for the current user and the current session. As soon as the user logs off, the mappings are deleted.

There are several types of devices that can be mapped to client devices in RDP sessions.

Client Disk Drives

Terminal Servers have the ability to connect to and map client drives from the local client device to the sessions running on the Terminal Server. When this is done, users have the ability to access data stored on their local hard drives or floppy drives from within their Terminal Server sessions. By default, client drives are connected as network resources. They show up in the user's explorer session as "C on Clientname." If you look at the open network connections in the session, you'll see a connection to \\TSClient\C. This connection allows users to access their local drives via a name they'll recognize.

In some situations, you may want to configure your Terminal Server so that it does not automatically connect to the client drives. If you do this, you can still configure it so that users can browse to their client drives through network neighborhood. To do this, make a change to the properties of the connection, which means that you must use the Terminal Server Configuration utility to configure it. Use this utility to edit the properties of the connection, and ensure that the "Connect client drives at logon" box is not checked (Terminal Services Configuration | Edit Connection | Client Settings). In order for this to work, the RDP client device must also be configured to allow client drive mapping.

Whenever any client devices are mapped from within RDP sessions, your users will see a "Microsoft Terminal Services" item in their Network Neighborhood (Network Neighborhood | Entire Network | Microsoft Terminal Services). Underneath the Microsoft Terminal Services item will be a computer called "TSclient." Browsing this computer will reveal the local drives shown as \\TSClient\C. These drive share names are made up of the drive letter as seen on the local client device, so they will see the shares as \\TSClient\C or \\TSClient\D.

If you would like to disable all access to RDP client devices' local drives, check the "Disable Client Drive Mapping" box in the connection's properties (Terminal Services Configuration | Edit Connection | Client Settings) or configure this setting via a GPO (as described in Chapter 6).

By default, most RDC clients do not auto-connect client drives for security purposes. It must be enabled on the client device.

Printer Mapping

Similar to the drive mappings, printers can be mapped with the RDP client software. Many different parameters will affect your printing solution in your Terminal Server environment. For that reason, you can find everything that you need to know about printing in Chapter 8.

Port Mapping

You can map LPT and COM ports from the local RDP client devices so that they are available to users via their server sessions. This is also configured as a property of the connection (Terminal Services Configuration | Edit Connection | Client Settings | Ensure that "Disable Client LPT Port Mapping" or "Disable Client COM Port Mapping" is not checked) or as part of a user profile. When you enable port mapping, the ports are not mapped in Terminal Server sessions automatically. Instead you can manually map them with the "net use" command much like a drive is mapped. (net use LPT1: \\TSclient\LPT1). The name of the client does not need to be known since the client device is always known within its own session as "TSCLIENT."

Audio Mapping

If your users' client devices have speakers, they can hear audio from their sessions on the Terminal Server. This arrangement is known as "client audio redirection" and works in a way similar to the other client mapping features.

If you decide to enable client audio mapping, you should know that only certain kinds of sounds are redirected to the RDP client devices. Only audio from applications in which the programmers "properly" used the Microsoft sound APIs fall into this category. Certain types of sounds that are played from server sessions do not make it to the client.

You'll need to test any applications that require sound. Microsoft designed the audio mapping capabilities of the RDP client so that the general "beeps" and "bings" that users receive throughout the day can be sent to the client. It's not meant to enable users to watch multimedia presentations from the server (although that can be done in many of cases).

On your Terminal Servers, enable client audio mapping as a property of a connection (Terminal Services Configuration | Edit Connection | Client Settings | Disable Client Audio Mapping box unchecked) or as part of a GPO (see chapter 6).

Clipboard Integration

When users run a combination of local and remote applications, they'll often need to cut and paste data from their local applications to their remote applications. Since both sets of applications are running on two different computers, this clipboard integration is not inherently possible. Fortunately, the RDP client software allows local and remote applications to share clipboard data.

When this feature is enabled, any data that is written to the clipboard of either the client or the server is instantly replicated to the clipboard of the other.

As with other configurations, clipboard integration is enabled or disabled as a property of a connection (Terminal Server Configuration | Edit Connection | Client Settings | Disable Client Clipboard Mapping check box) or via a GPO.

Window's Key Combinations

Within Windows environments there are several key combinations used to focus Windows or bring up the security menu. An example of these is ALT+TAB, or CTRL+ALT+DEL.

By default, these key strokes are captured locally on the client device and are not sent to the Terminal Server session. In some environments, users might need these keystroke combinations within their RDP sessions. Imagine that an application running on a Terminal Server requires the user to press CTRL+ALT+DEL. How would the user do that from her Terminal Server session? If she presses CTRL+ALT+DEL on her local client device, the local CTRL+ALT+DEL screen will pop up, not the one on the server.

In order to send CTRL+ALT+DEL to the server, the user must configure her RDP client to send these combinations to the server for execution. This is truly a client side setting that cannot be configured on the server. The only place to configure this is on the "Local Resources" tab of the RDC client. You can configure it to use the key combinations on the local client only (default), the remote server only, or send to the remote server while you are connected to it in a full screen mode.

Color Depth

One advancement of Windows Server 2003 is the introduction of support for up to 24-bit color in RDP sessions. The new client supports 8-, 16-, and 24-bit color. In general, the higher color depths add overhead to the bandwidth used by the client. The amount of overhead varies greatly depending on the types of applications being run, but testing shows it's about a 2-3kbps increase each time you increase color depth.

Client Performance Enhancing Options

In addition to the various features they support, several of the RDP clients also have capabilities to increase the performance of the RDP session. This is done in several ways. (Full performance tuning details are discussed in Chapter 13.)

Bitmap Caching

Some RDC clients have the ability to cache bitmap images from the Terminal Servers increasing the performance of a session since popular screen objects can be retrieved from the local cache instead of from the Terminal Server. Bitmap caching is generally beneficial, especially with applications that have a few main screens that most users flip through. It also works well in WAN environments.

In Windows 32-bit RDC client, bitmap caching is enabled via the "Experience" tab. Once enabled, the client begins to cache bitmaps into a BMC file located on the client device in the c:\Documents and Settings\<username>\Local Settings\Application Data\Microsoft\Terminal Server Client\Cache folder.

As you can see by this path, the bitmap cache is stored under the "local Settings" folder, meaning that it's not replicated as part of a roaming profile. Writing this chapter via a Terminal Server session with Microsoft Word 2003 created two cache files that were 8 and 19MB in size.

Themes

You can use the RDP client to disable Windows Server 2003 "Themes." Disabling themes simplifies the graphic layout of the Terminal Server session, thereby decreasing the amount of graphic data that must be sent to the client.

Menu and Window animation

You can also adjust how the Terminal Server shell draws its menus and windows. By default, Windows 2003 "rolls" the menus down. While pretty to look at, it also means that more graphic data would be sent to the client device in Terminal Server environments. Most RDP clients allow you to disable menu and window animations for their sessions, potentially saving bandwidth.

Show Contents of Windows while Dragging

As the name implies, you can choose to not show window contents while dragging (causing window dragging to look as it did in the old days—a simple wire-frame outline is drawn instead). Just like the other animation-related client performance options, disabling this option can increase performance since less graphic data is sent to the client.

Desktop Background

The final option that you can disable to increase performance is the Windows desktop background image. Again, this option can be disabled on a client-by-client basis. When disabled, a blank Windows desktop background is displayed instead of any images or active desktop content that users have stored in their profiles.

Which features are supported on which platforms?

The previous section outlined the generic options available with RDP clients. It's important to note that not all of these options are available on all client platforms. The chart in Figure 10.1 shows several popular RDP client platforms and the specific options supported on them. (An up-to-date version of this table is always available at www.brianmadden.com.)

	Win32	WinCE	Mac OS X	RDesktop	HOB Java	TS DOS	Palm OS
Drive mapping	•	•	•		•
Printer mapping	•	•	•	•	•
Port mapping	•	•		•
Audio	•	•	•	•	•
Clipboard Integration	•	•	•	•	•
Windows Key Combinations	•	•	•	•	•	•	•
Bitmap Caching	•	•	•	•
Compression	•	•	•
Encryption	•	•	•	•	•
Smart card redirection	•	•

Figure 10.1: RDP clients and the features they support.

As you examine this chart, keep in mind that it only shows the options that could be used on different client platforms. As an administrator, you have the ability to restrict certain options from users, and many of these restrictions can be configured in several places. The Appendix of this book contains a chart detailing every configuration option (those shown below and then some), and the location at which each option can be configured.

Now that you've seen the options available to various client platforms, let's take a detailed look at the most popular client for the most popular platform.