Re: Debian-Edu, Skolelinux and NX protocol (access from the internet) ?
mandag 17. mai 2004, 17:01, skrev francois schnell:
> Unfortunately I see one major problem for the wide spread of this
> linux based solutions : X protocol is heavy, it works well in the
> network of the school but if you want the students to have access to
> their applications from an internet connection there was no way to
> compete against RDP from Microsoft (or ICA from Citrix).
Pupils in lower grades often work with graphic rich applications. Then
the bandwidth usage in ICA is as high as bandwidth usage in the
X-protocol. When the government are carrying through national
centralised tests[1] in English over Internet, the media rich
Flash-applications will eat bandwidth on thin clients.
[1] http://info.nationaltests.no/
A lot of ICT-departments in Norway has sold the ICA-technology as and
Skolelinux/LTSP-killer. They use to much bandwidth is their
predictions. We just need 2 Mbps to server 30 thin clients with ICA
they say. Skolelinux needs 60 Mbps on the same amount of thin
clients. My concern is the problems this "over sale" creates when the
ICT-department has to move the Windows thin client servers from a
central point to every school, or they have to buy 100 Mbps bandwidth
to their schools. The price for that will exceed the cost with LTSP,
both in bandwidth, the amount of servers serving ICA thin clients, and
the administration cost with ICA that exceeds the
Skolelinux-black-box-solution.
The bandwidth requirement[2] with ICA thin clients are low with
mouse-gesture and clean text. An ordinary office-worker regularly uses
text-input within a word processor or an client connected to an
mission critical database. But the ICA nor the RDP protocol don't add
any compression to graphics that is already compressed. The
ICA-protocol can cache the graphics locally, but it don't has this
ability with moving vector-graphics, sound clips and when a user edit
images.
[2]
http://support.citrix.com/servlet/KbServlet/download/616-102-8139/ICA_Client_Bandwidth_Analysis.pdf
The Tolly Group published a report about Thin-Client Networking[3]:
Bandwidth Consumption Using Citrix ICA in January 1, 2000. The
synopsis gives a hint why a RDP or ICA-dependent solution don't
delivers the promised WAN access that many ICT-departments believe.
[3]
http://techlibrary.wallstreetandtech.com/detail/RES/949701776_555.html
In order for network managers to plan accurately for bandwidth
demands in a thin-client network utilizing Citrix Systems, Inc.'s
ICA protocol, they must know the bandwidth requirements for common
functions/states. If bandwidth demands are underestimated or
unknown, severe congestion could result on the network. Such
congestion could impact the ability of network managers to deliver
on contracted service-level agreements or provide adequate network
support for time-critical remote applications. Tolly Research
benchmarked the bandwidth consumption of common office applications,
functions and machine states that are likely to be encountered in an
enterprise network. Because much of the bandwidth consumed for
thin-client networking supports updating and refreshing the client?s
graphical display, researchers segregated their investigations
between applications that place significant demands on the graphical
refresh and those that do not.
* NX don't solve the media-rich bandwidth requirement
When applying nomachine-technology (NX), the "media-richness" also
hits the bandwidth barrier. So we probably need the next level of thin
client technology on Skolelinux with both NX that compresses X, and
the ability to handle media-rich content with programs running on the
thin client CPU. I'm talking about a kind of half-thin clients where
media-rich applications as XINE, Flash-Plugin or Java runs on the thin
clients CPU. The rest of the applications runs on the server.
http://www.ltsp.org/ltsp-4.html#localapps
At least 2 companies ask for this solution in Norway. I told them that
the technology is there, but has to be combined together, and made
"out of the box" ready with the free software developers in KDE,
GNOME, Debian and X/freedesktop.org organisations. I also told them
that the work probably has to be done with qualified open source
developers. They has to be persons with track-record and ability to
deliver. We also needs extensive test environments.
- Knut Yrvin
Project Manager Skolelinux Norway
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