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Re: [ndt-dev] Expose 2 new Flash variables to JS

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  • From: Richard Carlson <>
  • To:
  • Subject: Re: [ndt-dev] Expose 2 new Flash variables to JS
  • Date: Fri, 19 Dec 2014 12:28:51 -0500

Hi Nathan;

I just ran the client on my home Linux workstation. Nice job, I'm pleased that NDT based on-demand testing will continue even if the face of growing Java JRE limitations.

While the client gave me the upload/download and RTT data, there was no way to dig into the test results to figure out if these numbers were good, bad, or mediocre.

As the original developer of the NDT code I will repeat my mantra, the server is collecting data that can be used to interpret the test results. I agree that the majority of NDT users are not interested in knowing more than the basic data, but I still think that M-Lab should strive to educate them on the value of knowing more.

For example, the NDT server calculates how the clients selection of TCP window size impacts the upload and download speeds. These are the upper bounds of what could be achieved over the connection. The server also calculates the speed based on the Mathis formula, this is also a bounding condition.

I think it would be great if the display somehow showed the user where they fit in relation to these limits.

At a minimum, I would also like to see a button on the screen that would send me the test details. Again, I know that few, if any, users want/need/understand this data, but the point is, they could look at it or send it to the IT staff when reporting a problem.


On 12/19/2014 11:45 AM, Nathan Kinkade wrote:
Hi everyone,

This is my first message to this list. I just started working with
the Measurement Lab team at OTI a couple months ago. One thing we're
working on is to put together a javascript wrapper around the Flash
NDT client to make it a bit easier and more flexible for people to
integrate the Flash client into various sites (originally written by
Collin Anderson [1]). The code can be found here:

And a working example can be found here:

As most of you are probably already aware, the Flash plugin in Firefox
and Safari on Linux and MacOS is woefully old and apparently cannot
reliably measure throughput at higher speeds. The current Flash NDT
client already includes code to detect these bad Flash environments,
however there is currently no way to communicate that (effectively) to
javascript. I've made a couple small changes to the flash-client
ActionScript which just set two new variables that are then exposed to
javascript. One variable is simply a true/false flag to the
javascript that the Flash client detected (or not) a bad Flash
runtime. The second variable is simply the prescribed message to
display to the user when a bad runtime is detected. If you load the
above working example in Firefox on Linux, you should see the error.
The patch to the flash-client ActionScript can be found here:

The other tiny change in the patch, which isn't really necessary, but
perhaps useful, is to enable debugging by default, which allows
javascript to access and possibly display, debug messages,
facilitating development.

I apologize in advance if this isn't the proper way/channel/method to
submit patches for proposed features or bugs. If not, then let me
know and I'll be happy to go through the preferred process.




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