Setting up infrastructure

Network architecture

User case: Shall set up a computer network that scales so that one can either operate the system locally or connect to a centralized operational solution

Solution

Exception handling

Verification

Update the configuration database

Server profiles

Use case: How to install machines for an entire computer network for a school or many schools in a municipality.

< FIXME: In with the drawing showing diskless clients>

<ul> <li><p>[ATTACH]</p> <p>The different profiles on different servers.</p></li></ul>

Combi-server as a combined resolution

Two profiles with main server and thin client server in combination are called a combi-server

This is a fairly small step, which makes it easy to use an appropriate switch on the backbone network, and use a crossover cable to connect the firewall with a combi-server

Note: Be aware that setting a printer on the address 192.168.0.0/24, which is the thin client network, does not work if the hostname is printer00. Be sure to edit KDE printing manager to search for printers at 192.168.0.0/24-net. Not standard 10.0.2.0/23-net.

Description of the profiles in Skolelinux/Debian-Edu

Profiles shown during the installation originate from the file src/debian-edu-install/debian/debian-edu-install.templates in the debian-edu-install package.

Graphical desktop

One will increasingly see references to a graphical desktop. In short that means a modern desktop with point and click, windows, icons, and file folders. Graphical user interfaces were first made by Xerox Parc in 1973, 10 years before they came to personal computers that could be bought on the market. This was a very short presentation of graphical user interfaces.

A brief summary of the different profiles in Skolelinux/Debian-edu and how they can be combined

<ol style="list-style-type: decimal;"> <li><p>Main server</p> <p>Warning: All Skolelinux/Debian-edu-networks must have only one main server, and only one machine with that profile. Most commonly that profile can be combined with thin client servers, or just a workstation.</p> <p>Every Skolelinux network needs one, and only one machine running the 'Main Server'. This machine provides network services such as for example network login with the help of directory server (LDAP) etc. Without this machine the network does not work. Since this machine will save all data files, it needs a lot of disk space. You do not get graphical user interface by installing this profile. If you want a graphical user interface you must also install workstation-profile or thin client server.</p></li> <li><p>Workstation</p></li></ol>

Machines running the 'workstation' profile is what we know as normal PCs. Users log on to workstations, and get storage space on The main server. Documents, personal settings and many network services are on The main server. User programs run on the workstation.

For access to CD/DVD-player/burner, digital cameras, scanners, this is the profile to install.

  1. Thin client server

Machines running the thin client server support the thin clients. This profile also includes the workstation profile. To prevent saturating the network, two NICs are required. The profiles: main server, workstation and thin client server can be installed on the same machine.

This profile also contains the work station-profile

  1. Diskless workstations

Machines running as thin client servers provide support for diskless clients if this is enabled. In Skolelinux 2.0 this must be enabled afterwards. This profile also includes the workstation-profile. Profiles main server, workstation and thin client server can be installed on the same machine.

This combination of profiles, also called combined profile, providing the ability to setup a complete Skolelinux / Debian-edu network workstations and thinclients with only one server. This is an acceptable solution in a small Skolelinux/Debian-edu network, with maybe 10-15 thin clients and a few workstations. For larger installations, one must usually choose servers which are larger.

  1. Main server + workstation

This combination of profiles mainly gives you a main server with a GUI. If you do not like the idea of administering your main server from the command line, this is a good combination.

The standalone profile is not part of Skolelinux/Debian-edu network. The purpose of this profile is to support the home PC or portables.

  1. Stand alone

The standalone profile can not be installed together with the main server, workstation or thin client server.

The standalone profile is best to use without linking it to a Skolelinux / Debian-edu network.

All programs in Skolelinux/Debian edu are included in the standalone profile

Solution

Exception handling

Verification

Update the configuration database

Hardware servers

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Client computers

User case: Choice of client machines. Should you choose silent machines or machines for multimedia. Should one have laptops to all or desktops.

Several types of technologies can provide application on the PC. Most common is thick clients operating locally on each computer. But there are other types of technology for applications on the desktop. Many have heard of graphic terminals. Examples include Citrix, !FreeNX and Windows Terminal Server. There are also other options like lowfat clients and real thin clients. This article describes the options and provides an overview of where the various terminal technologies do best. The reason for the article is the experience of enterprise solutions with centralized operation of the computer in many different buildings with low, medium or high network capacity.

Client technologies are described in the following order. Graphic terminals Citrix and !FreeNX, thin clients with X Windows, thick clients with Linux and Windows, client in between with Linux, and laptops. The following are examples of what server systems are commonly used in various business-oriented installations. A key factor for calculating costs is the number of concurrent users and the number of servers. Centralized management of computer equipment at several schools may in practice be compared with how the operations of ICT systems is done in larger companies. Often schools have more computers than the rest of the council's activities. Failure to think things through in what one chooses for client solutions in schools can quickly lead to a doubling of the number of employees in IT services in the municipality.

Citrix is the most known product for graphical clients. The company making this is product was established in 1989. The first graphical clients were made for the operating system OS/2. First Windows product was launched with NT 3.51 in 1995. There are several competing products to Citrix. One of the most successful is the NX technology. Briefly, you may run applications from a server with Citrix or NX. The screen is exported over the network from a server to a graphical terminal on a thick client.

Graphical clients have the strength that it would be seemless what ever kind of operating system that might be running on the client. One could use the applications on the server anyways. One can run standard office programs and client emails over an ISDN line with 64 kbps. That said, there are limitations in graphic software, whether it is used with multimedia or interactive graphics. The solution can quickly become of no practical use if a municipality distributes 30 or 50 graphic terminals at 5-6 schools with broadband with 2-8 Mbps. With this capacity one can not run interactive graphical applications. The Internet would be filled up with traffic, and the Citrix client would disconnect from the server machine.

With graphical clients the operations department must run two parallel paths for the maintenance of software. Maintenance occurs on all client computers and on local and central servers. For getting for example Citrix to work reasonably well, there must be deployed two additional server machines in each building, in addition to central application servers. In addition, it usually needs some thick clients also for use with multimedia. For example 1/3 of the machines in Oslo schools are thick clients to provide support for multimedia.

Thin clients was introduced in 1984 at MIT. This was around the same time Apple released the Macintosh GUI. The following year Microsoft shipped the first edition of MS-Windows. Actually thin clients are named X Window Systems and can be used on all possible platforms like Linux, Mac or Windows. X Windows turned things upside down. In practice applications run on a server, and the GUI is sent over the network to the client computer. The client computer runs a server program to display graphical windows. An X server may run your application windows from different programs running on many different servers. Thick clients also run the X Window system, using a virtual local network on the PC. All Unix systems with graphical user interfaces run X servers.

The main advantage of thin clients is the reuse of older equipment without increasing the complexity of operations. Many people use PCs with 233 MHz and 32 MB memory as thin clients. There is no need for local hard drive. Users can handle heavier graphics, sound and simple video. Several schools have opened up for the use of CD / DVD-Rom and USB memory stick at the thin clients. Operating personnel do not have to keep track of a separate operating system on each of the PCs. Everything is handled from the server. Each thin client uses around 2 Mbps network capacity during normal use. The performance of thin clients is significantly better than graphic terminals. Thin clients need in average fewer servers than graphic clients with for example Citrix, as shown by a study of The Department of Education in Oslo.

Thick clients or standard PCs is what is mostly used today. The term Personal Computers were used for the first time November the third 1962. The first PC with network and graphical user interface was created at Xerox PARK in 1973. Today it is the PC concept IBM launched in 1981 that is known and widespread. The entire operating system and all the software applications are installed on each client computer on a local data store. The most famous operating computers are Microsoft Windows and Linux. But there are also a number of other systems that many people use, including a version of BSD.

The advantage of Thick clients is that all programs are run locally, which can provide great flexibility and performance for users. Since most user programs run locally few central servers are needed. Solutions with thick clients can be relatively inexpensive to operate if one standardizes. On Windows, it is a great advantage to have mostly similar machines, which is difficult over time. It is quite common, for example, that the school has both 4 and 5 PC types. This affects operational costs. Linux is more flexible because the system can be more easily managed with many different PC types. Linux also requires less memory, and allows for longer use of older computers without loss of performance as the British Educational Communications and Technology Agency (BECTA) reports.

Diskless clients is another exciting technology. Today supported on Linux with Lessdisks or new LTSP. Novell had a virtual monopoly on diskless clients 15 years ago. Simply explained, the entire operating system and applications are installed on a server. The operating system is uploaded from the server to the client over the network. File, print, and Web services are handled by an operating system designed for networks. By the introduction of Windows 95, Novell met a technological barrier. Microsoft changed controlling Windows with registry instead of text files. Now it's only Linux and other Unix variants offering diskless clients.

The advantage with diskless clients is that you get the performance of thick clients with the operational advantage of thin clients. It means that the organisation can connect many client machines to a server, without installing locally an operating system on each client. Everything is handled from the server. The system supports audio, video, CD/DVD-Rom and USB memory stick. Today it is unusual to find used machines with less than 800 MHz processors and 256 MB of memories, which is well suited for the half thick clients. It is recommended to use local hard drive cache.

Portable machines are essentially thick clients. Laptops may in principle be used as thin clients, half thick clients or graphical terminals. But it is not very practical for several reasons. Portables should be used as thick client. In order to connect the laptop to a stationary computer network, one must choose what kind of services to be used.

There are significant challenges with portables in wireless networks with many users. Wireless networks have limited capacity. Portables are also subject to rough treatment, and require more frequent replacement than what is normal for stationary equipment. One should not run graphical terminals on laptops in wireless networks. This quickly becomes unstable when you have many users. Thick clients with Linux or Windows run fine. They can relatively easily be authenticated against the network. The user can access file directories, printing and other network services in a safe and secure manner. Several providers offer laptops in schools which connect to the computer network running Debian Edu.

Table of client types

Main solution

Support for multimedia

Characteristics

Fat clients (Windows, Linux or Mac)

Good support for sound, graphics and video with powerful enough processor and memory on the client machine.

All user applications installed on the client machine. The user programs run on the client machine. The client machine may be stationary or portable. Running multiple services in networks such as email, file storage, case-filing system etc.Advantage: Requires few server machines. Good support for multimediaDisadvantage: Need to install and maintain all the software on each client machine

Diskless workstation (Linux. Earlier this was the solution from Novell with Windows 3.X)

Good support for sound, graphics and video given a powerful enough processor and memory on the client machine.

All user applications are installed on the server machine. User programs run on the client machine. Client computer is usually stationary. Running multiple services on the network such as email, file storage, case-filing system etc.Advantages: Same functionality as thick clients. Need few servers. The client computers do not have software installed.

Thin client (X Window System)

Decent audio, graphics and video support given a powerful enough processor memory on the server machine. Needs high capacity client network.

All user programs and services are installed on the server machine. The user programs running on servers. The client computer is usually stationary. Running multiple services in networks such as email, file storage, case-filing system etc.Advantage: Gives new life to reused computers. Client does not have installed software.Disadvantage: Requires more servers than thick and diskless clients.

Graphical terminals (FreeNX, Citrix, RDP)

Decent graphics support given powerful enough processor memory on the server machine, and high capacity network. Weak or little support for interactive graphics at medium capacity network.

All user programs and services are installed on the server machine. A full operating system with a graphical interface is usually installed on the client machine. The user programs run on the server. The client computer is usually stationary. Several network services such as email, file storage, case-filing system etc. are provided.Advantage: Gives new life to reused computers.Disadvantage: Must install and maintain the operating system on each client machine. Requires more servers than real thin clients. Requires significantly more servers than thick or diskless clients. Gives poor performance or no support for multimedia. The terminal disconnects with network overloads. This may happen several times an hour.

Laptops

Good support for sound, graphics and video with powerful enough processor and memory on the client machine.

Advantage: Can take the PC anywhere suitableDisadvantage: Must install and maintain the operating system on each client machine. Must set up and maintain services that make it easy to connect and disconnect machines on the network. There is considerable breakage with portable equipment, and lifetimes average 3 years; that's 2-5 years less than desktops. Administration of portable devices is expensive.

Solution

Exception handling

Verification

Update the configuration database

Switches

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Wireless access points

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Firewall(s)

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Routers

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Setting up a simple firewall

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database

Setup:

User case: What's should be configured

Solution

Exception handling

Verification

Update the configuration database