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
