Linux Thin Client : Considering the Network

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Primary Network

Your first thought might be that your current network will work fine with thin clients and that is entirely possible. But your network might be something that has grown through the years and is not that well designed. Your implementation of thin clients then might be a good time to review the design and make upgrades as needed.

Personal Computers versus Thin Clients

Based on conversations with some hardware vendors, it’s clear that most of the testing is done with the expectation that personal computers willbe deployed.

The biggest difference is in how the two platforms use the network. When running a personal computer, often software applications are stored on network servers. When you activate an icon, the network pushes the executable down to your PC. Once downloaded into memory, the application runs and then very little interaction takes place until you save a file. Or in other cases, the executables are on the local PC, and network activity is not used until files are saved. If an executable takes a few seconds longer to download, you won’t      really notice it when using a personal computer. Some networking devices seem better designed for efficiency of download instead of being designed for the smaller and more plentiful packets of network computing. When you activate a software application on a thin client, the presentation of the user interface is pushed to you from the server, and then all keystrokes and mouse activity are transmitted back and forth to the server in real time. The network needs to be very fast, have low latency, and be configured to pass packets immediately to the servers.

Network Design

For implementing your network, the network backbone should be Gigabit if possible. Obviously if your solution is for only a small number of users, this might not be required. Ideally fibre optic lines are then run to each of the wiring closets, and each switch should have it’s own line. It is advisable to avoid daisy-chaining the switches together in order to avoid any kind of contention between them. The servers are all plugged into the backbone at Gigabit as well. If a server is required away from a centralized computer room, then it is better to run a separate line instead of plugging it into a switch that will be shared with thin clients. It’s important to keep the data paths solidly designed so that all of your real-time interaction will not be delayed.

X windows, RDP, or Citrix are used to display the user presentation. This means that the software is running on the server, but the image of that software is transmitted over the network. It’s important that a strong network exists or repaints of windows will be slower and feel sluggish. This issue will cause people problems, with perceptions that a personal computer can run software faster than a network. A correctly designed network will provide excellent response time and the user community should not even see a difference.

Font servers are used to distribute fonts to users. A font server is just a process or application that runs on the server. When a user requests a font, it’s sent over the network to the thin client and made available to them immediately. The strength of this design is that all your employees will have the same fonts and while sharing documents, they will render exactly the same way no matter from where you log into the network. Anyone that has shipped documents between personal computers with different fonts, will greatly appreciate this design. When the network is configured correctly, font download and interaction is immediate and undetected by the user community.

NFS mounts are used to connect disk drives between Linux servers. This allows applications to share data between the various servers on your network. Response time needs to be excellent to provide very fast file saves and retrievals, at the same time avoiding applications that lock or timeout while trying to interact with files.

A review of the possible network problems is provided in the following table:

Networking Issue

Symptom(s)

X windows

RDP

Citrix

Slow repaints of user interfaces

Lockups

Disconnections

Font Servers

Slow repaints

Wrong fonts in applications

Thin Client

Slow keyboard response

Disconnections

Slow repaints

NFS Mounts

Lockups

Slow response in saving files

 


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