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The Administration uses thin desktops with access via Citrix or similar to a mixture of Windows and Unix applications.
The use of the BRA is not assumed here as the original reasons for using a thin client model are still likely to hold. However if a move to the BRA is contemplated then many of the same problems in Scenario 1 will arise. Migration in this Scenario under this assumption is therefore very simple as the architecture is not going to change.
Because the client is very thin all that is required is an OSS viewer for each protocol required. The windowing system doesn't need to have a great deal of functionality so a light weight manager like tvwm would be sufficient.
The following protocols can be supported (among others):
HTTP. Any OSS browser would be sufficient. The ability to run Javascript and Java would need to be investigated. In addition, any plugins required would have to be supported directly, through a substitute using the plugger package or through the proprietary CodeWeavers CrossOver Plugin package.
ICA. This is the proprietary Citrix protocol. Citrix provides a zero-priced, but non-OSS, ICA viewer which works under GNU/Linux.
RDP. This is the protocol used by Windows Terminal Server. An OSS viewer for RDP, rdesktop, is available.
VT220, VT100 etc. These DEC protocols are all supported by xterm using the appropriate TERM environment variable setting. Connection to the host is made via telnet.
xterm can emulate many different terminal types by changing the value of the TERM variable. For instance setting TERM=prism9 will emulate the protocol used by PRIME machines. All the emulations assume telnet connectivity or similar and a character-based rather than page-based protocol.
3270. The x3270 program provides the appropriate support. Connection to the host is made via telnet.
X. This is the native display protocol on GNU/Linux and so should provide no problems.
There are proprietary products for some of the more esoteric protocols.
The Linux Terminal Server Project (LTSP) http://www.ltsp.org/ provides a number of kits to build thin client devices based on GNU/Linux. This is an extremely active project and the quality of the software seems to be very good.
The changes required on the servers are similar to the considerations discussed under other Scenarios.