The core difference between Windows NT 4.0 Terminal Server Edition and MetaFrame is the protocol the clients and the server use to communicate. Both are proprietary implementations, but of different origins.
Citrix' Systems, Inc.'s Intelligent Console Agent (ICA) protocol has its origins in OS/2. WinView, the company's first product, let remote users access 16-bit Windows applications running on an OS/2 server.
Microsoft Corp.'s Remote Desktop Protocol (RDP) is based on the International Telecommunication Union's telecommunications standards division's T.120 series of protocols. Originally designed for videoconferencing, this family of protocols has been layered on top of a diverse set of network protocols and media.
In particular, RDP is an extension of the T.128 standard for Multipoint Application Sharing. Microsoft's version has been modified to work in point-to-point mode (between the client and the server) rather than in a multipoint configuration (among several peer machines) as defined in T.128.
RDP lags behind ICA when it comes to the features it supports. The table below describes the differences between the two protocols.
|
Microsoft RDP |
Citrix ICA |
|
|
Standard basis |
Proprietary extension of T.128 |
Proprietary. Developed by Citrix |
|
Network or transport protocol support |
TCP/IP |
LAN: TCP/IP, IPX, NetBEUI. WAN: PPP, Async modem, ISDN, Frame Relay, ATM |
|
Data compression |
No |
Yes |
|
Packet-level encryption |
No |
Yes, Secure-ICA version |
|
Works with RAS* |
Yes |
Yes |
|
Shadowing** remote sessions |
No |
Yes |
|
Can disconnect sessions |
Yes |
Yes |
|
Desktop/ application access |
Desktop View only |
Desktop View; Independent "Seamless" Application Windows |
|
Desktop window sizes |
640x480, 800x600, 1024x768, 1280x1024, 1600x1200 |
640x480, 800x600, 1024x768, 1280x1024, or custom |
|
Client color modes |
16, 256 colors |
16, 256 colors |
|
Network audio |
No |
Yes. Compression available |
|
Client local device access |
Yes (printers only) |
Yes (modems, printers, serial ports) |
|
Client local device sharing |
No |
Yes |
|
Client local hard-drive access |
Yes, local drives letters remapped |
Yes, local drive letters remapped |
|
DOS client support |
No |
Yes |
|
16-bit Windows client support |
Yes |
Yes |
|
32-bit Windows client support |
Yes |
Yes |
|
UNIX client support |
No |
Yes, with UNIX ICA client (Solaris, AIX, HP-UX) |
|
Other clients |
None |
Java, MacOS, OS/2, ActiveX |
* Remote Access Services on NT
** Shadowing is remote session viewing and control by an administrator.
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