1) Introduction
First, a presentation on Windows Terminal Server is required. This is a service that was originated at Windows NT 4.0, and its function is to allow remote access to a given computer, through a protocol called RDP (Remote Desktop Protocol). This protocol is encapsulated in a TCP/IP connection, and transfers data from video, mouse, and keyboard between host (machine accessed remotely) and client (machine where the connection comes from, and the host’s remote operation).
Just like Windows Terminal Server (from now on just Terminal Server), E3 Viewer is also a module developed for a system’s remote operation; in this case, a project installed in an E3 Server. The difference is, besides from Terminal Server’s generic character, in the way data transfer between host and client is implemented.
2) RDP (Remote Desktop Protocol)
This protocol was developed by Microsoft to be available for all versions of Windows from NT family (NT 4.0, Windows 2000 Server, Windows XP Professional, and Windows 2003). It allows interaction between a client computer and a host computer (which will be accessed remotely), through the transference of video, mouse, and keyboard data from the client machine.
Windows Terminal Services works in different ways, depending on the version of Windows installed:
- Access Licenses: it is possible to enable a greater number of licenses for Windows Terminal Services at Windows 2000 Server and Windows 2003. However, these licenses imply in financial cost, which should be checked with Microsoft. Windows XP Professional, on the other hand, has the option of enabling a remote connection.
- Simultaneous Access: host Windows (2000 Server and 2003) can be accessed as much as the number of licenses they have. Nevertheless, XP Professional’s local operation interface is closed when a remote connection is opened, and this version’s typical welcome screen returns.
- Requirements: to access a computer remotely, via Terminal Services, it is necessary that the software Remote Desktop Connection (easily found at Microsoft’s homepage) be installed in the client machine. This software can run on any 32-bit version of Windows (which means that from Windows 95 on, any version can access a remote desktop).
The license control is done by E3Server that verifies the amount of E3Viewer and E3Studio licenses available.
3) E3 Viewer and REC (Remote Elipse Call)
REC is the protocol developed by Elipse Software for the communication between E3 Viewer (which is the responsible for the operation and the interface with the user in a given domain) and E3 Server (which runs this domain).
This protocol was created to replace most connection functions offered by COM/DCOM services, previously used for communication between modules at E3. This change was necessary because of the use of TCP/IP ports allocated dynamically by these COM/DCOM services, among other technical characteristics. This hampered E3 Viewer’s operation via Internet, since maintaining these ports open could cause serious problems of hacking corporative network.
E3 Viewer always uses the same communication port to access E3 Server, and information exchange between them always occur via REC protocol, which is transparent to the final user.
The important features about E3 Viewer are:
- It is always licensed at E3 Server, which controls the available licenses for a given project.
- Its connection depends exclusively on a network path, and on 6515 port open in network’s proxies and firewalls.
- It is the software that implements REC protocol; that is, all calls made by E3 Viewer to E3 Server are sent via REC protocol, so that all protocol’s specifications can be hidden from the final user.
- Each E3 Viewer being executed on the network (be it Internet or Intranet) will use one license available at the host.
- The same E3 Viewer’s license can be used in different machines on the network, as long as these machines do not access E3 Server simultaneously.
- E3 can be executed in machines where either Windows 98 (E3 Viewer W98) or Windows 2000 or XP Professional (E3 Viewer W2k) are installed, with the same functionalities of any operational system.
Advantages and Disadvantages
With the information above, it is now possible to analyze the advantages and disadvantages of each of these options described before.
The point of this section is to compare E3 Viewer’s use of multiple licenses with Windows Terminal Services use of one single license.
E3 Viewer
|
ADVANTAGES |
DISADVANTAGES |
| License centralized at E3 Server. | It is necessary to install the software E3 Viewer in each machine where it will be executed, in an appropriate version for the operational system. |
| Independent from Windows configurations. | |
| High graphic resolution, with resources like zoom, screen size automatic adjustment, etc. Resolution depends only on the machine where E3 is installed and running. | |
| Communication with E3 Server is optimized, so that there is almost no latency in the communication between host and Viewer. | |
| It is possible to block access to Windows work area. | |
| User control is independent from Windows. |
Terminal Services
The advantages and disadvantages of Terminal Services will be analyzed only when it is being used with Windows 2000 Server, XP or 2003.
|
ADVANTAGES |
DISADVANTAGES |
| Licenses configured at the host (Windows), in a centralized way. | It is necessary to configure host Windows to allow multiple access, including user configuration, among others. (Windows 2000 Server or 2003 only.) |
| “Intelligence” runs entirely on host, requiring lighter clients than if Viewer had to run on these machines. | Additional access is charged as independent licenses, generating financial costs, when using Windows 2000 Server or 2003. |
| E3’s project can be used in any type of Windows, using a remote access. | It is necessary to install Remote Desktop Connection module in all client machines. |
| Ideal for projects where graphic quality does not compromise the operation. | Requires a host with more resources, for it will run a heavier operational system, and will also treat the remote connections received. Not to mention E3 Server, which will execute E3’s domain. |
| The ideal tool to purify large-scale projects, for it allows access to all resources in the computer, obeying the restrictions done by E3Viewer, when necessary. | A poorer graphic interface, for video data are transferred via network. Besides, operation can be slower than E3 Viewer’s. |
| Allows access to machines that use operational systems such as Linux and Windows CE, as long as Remote Desktop software is installed in this machine. It expands E3’s reach for these operational systems. |
4) Conclusions
Analyzing carefully each case and choosing the best way to implement multiple access licenses to an E3 Server is a complex task, which requires clear goals. The financial costs of both services are similar, depending on the package offered by Elipse or by Microsoft. The cost of the installation is similar, and depends on the packages offered by Elipse or Microsoft.
E3 Viewer’s advantages, being it the software designed specifically for E3 Server’s remote operation, are high-quality performance and graphic presentation. Terminal Services advantages, on the other hand, are higher reach and lower processing capacity in the client machine, not to mention the possibility to operate E3 in other software platforms not supported by E3 Viewer, such as Windows CE and Linux.
Selecting the better option is a task that can bring great benefits, both technical and economical, to E3 user.
