Knowing the Bandwidth that your users have to your data centers can help you determine how rich or light your site needs to be. The Bandwidth distribution chart divides your users into well known bandwidth blocks and reports on how many users fall into each block. You can further drill down into a single bandwidth block to analyze your site's load time histogram, browser and geographic distribution for users within that bandwidth block.
Using Bandwidth Measurement?
There are two steps to using bandwidth measurement:
Download the bandwidth measurement images from the mPulse Resources page. You have the following options to arrive at the Resources page:
Home page - The Resources page link is located on the bottom-left side of your screen.
Central - The Resources page link is located on the bottom-left side of your screen.
Specify the folder including the trailing slash at the end of the URL string (required).
Add the bandwidth images location to the mPulse Domain by entering it in the Bandwidth measurement images location field, which is located on the General tab in the Configuration screen of your app.
Optionally, define a Sampling Percentage. mPulse will enforce a sample rate as a percentage of total bandwidth when Enable bandwidth test is checked and is also accompanied by a rate entered into this field.
Note: Users should be aware of the potential impactfulness of the sample rate specified here and proceed cautiously, especially when mobile devices are involved. For example, if 1M mobile devices were involved by the given rate specified, the traffic generated by that would be in the neighborhood of 40TB of data.
Sampled bandwidth testing will permit mPulse users tracking large sites to adjust the percentage of the population that bandwidth testing is run against, thus controlling costs, as well as resource consumption during testing.
Placing Bandwidth Images—Origin Server vs. CDN
The decision where to place bandwidth images—on your Origin server or on your CDN—depends on what you want to measure, and how your CDN provider charges you. There are two things to consider:
The images are not cached on the client, and we use cache-busting query string parameters to force an image reload. This is necessary to make sure we're testing the bandwidth to your server and not the bandwidth to a local cache. If you put the images on your CDN, your CDN will make a call back to your origin server every time a user gets tested. This may not be the best use of your CDN. If you can configure your CDN provider to ignore query string parameters for these images, that might be useful.
What do you want to measure? Do you want to measure bandwidth to your origin server or to your CDN? This is largely a personal preference of the site owner.
Setting Cache-Control Headers for Bandwidth Images
Since mPulse uses cache-busting query string parameters that change on every image request, the browser will ignore any Cache-control, Expires, and Last-Modified headers sent along with the image. To make the test as accurate as possible, it's best to send as few headers as possible when serving these images.
If you're unsure of what to do, do nothing. The defaults for most web servers are suitable.