Re: How bandwidth requirement could be reduced when using thin clients?
tirsdag 05 oktober 2004, 04:05, skrev Vagrant Cascadian:
> that's why i was wondering if you were exploring lessdisks as a
> "half-thick client", because the memory and CPU requirements seemed
> high for a typical lessdisks "thin-client".
I think I'll give a more strategic background for why we ask, and what
the expectation are from the municipal department of education in Oslo.
We already have thin clients with LTSP in Skolelinux. A lot of
schools uses the preloaded architecture with huge success in Norway,
Europa and Africa[1] - even in Hawaii[2]. The architecture[3] in
Skolelinux is made for low bandwidth. It allows use of Internet on a
telephone modem (28.8 kbps), and the maintenance could be done by a
ssh-tunnel. You can use the network with no Internet at all. The
architecture is fully expandable. Different IP-services can be placed
on it's own machine, or in a central centre of operation with small
changes in the DNS. This is already in production in The Norwegian
research network[4] that is in a migration process to Debian,
inspired by the Skolelinux effort.
[1] http://www.fair.no/english/about_fair.htm
[2] http://www.desktoplinux.com/news/NS6201542989.html
[3] http://developer.skolelinux.no/arkitektur/arkitektur.html.en
[4] http://www.uninett.no/index.en.html
The municipal department of education in Oslo expect us to place the
application servers centrally for 175 schools. The idea is that all
the servers should be placed in one building, and they should rely on
heavily use of thin clients on a serverfram. At our first meeting they
told us that they had solved this with Windows and Citrix. In real
life it's like this:
1. The Windows thin clients have heavy restrictions, where media rich
applications is not an option, which is application that is based on
Flash, Java and streaming.
2. They have placed 1-2 servers at the schools give access to
reasonable login with Active Directory, replication of files to
"multimedia-ready" workstation, and some Internet services.
3. The bandwidth limitation to the schools are between 2-8 Mbps. The
schools have 90-150 workplaces where 80-90% are thin clients, and
the schools have 10-20% workstations to tackle media rich
applications (Video editing, Flash, Java etc.). It works, but it's
not especially impressive.
Anyway.
1. In our believe we need a server at the school in some form
or another anyway. We are technicians, and know that the network
gives some limitation. We really want to give the pupils media
rich application if all the servers are placed in a centralised
serverfarm - because the national exam's in English is
mandatory, made with a Flash application:
http://www.intermedia.uib.no/projects/bite-it
Today many schools has tested the national exam with Skolelinux,
and it work as expected with todays architecture.
2. The pupils and teachers don't know the difference between thin
clients and a workstation anyway. Then we need to give them Flash
and Java (goods forbid). Through testing we know that some of the
Flash-applications eats bandwidth in the LTSP-setup. The standard
use i 2 Mpbs for every client. With some applications it is 10
Mbps. We really wants to reduce that in our standard setup. This
has to follow our black box idea where everything is done
automaticly, as our architecture and installations shows.
3. Even if we have already solved the problem with media rich
applications with our black box approach, and it's in use in whole
of Norway, The municipal department of education in Oslo wants a
server farm - period. An even if they don't really have that today,
our mission is to support that idea. And some of the people we talk
to, almost all, did not listen to our argument that it's no problem
to maintain and operate a large "black box" solution for all the
schools, making Flash-based English exams working much better than
today etc.It's also an argument about cooling and housing (a
room) for a local server at the schools.
4. The people on the other side of the table lacks some insight about
networking in large where you make a IP arcitecture that takes care
for the bottleneck. When we make this report it will be well
documentet what the possibilities are. By the way -- it's the
politicians that want this done. They have cut the budget from 60
million to 20 a year, with a clear message. Give Linux a try - you
don't get more money.
5. So now we explore FreeNX to copy the Citrix-solution 100%. We also
need to place some applications on the thin client, just to speed
up Flash, and reduce the bandwidth requirement when using FreeNX,
because running FreeNX with Flash gives bandwidth requirement with
500kbps in peak, even if the standard bandwidth is between
20-40kbps (as we have demonstrated with a standard
NoMachineNX-server/client). To sum it up, we want to move the
Flash-applications, Java, and streaming applications (mplayer) from
running on the thin client server, to run on the thin client.
We want to surpass the Citrix-solution by taking the best parts from
free software when reusing PC as thin clients. Some older PC are
Pentium 133 MHz with 32 MB RAM, others are 450 MHz with 128 MB RAM.
Our investigation is to put the "moving parts" on the client, and
choke the bandwidth requirement between the server and the client. We
want to show the ICT staff that it can be done even smarter than the
Citrix-way, with give media-rich application a real life and user
experience on the thin clients. They can choose. Do it the Citrix way,
and you get less for your money. Do it the smart way, and you really
get speed out of the newer reused machines.
- Knut Yrvin
--
Project manager (cel: +47 908 95 765) Skolelinux Norway and OpenOffice
translation to Norwegian. Office 1: SLX Debian Labs Forskningsparken,
Gaustadalle 21, 0349 OSLO, NORWAY. Office 2: IT-Staff Akershus County
Council, Schweigaards gate 4, 0185 OSLO, NORWAY
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