Emulating slower network traffic

You can emulate various WAN connection speeds used for HTTP traffic to determine its effect on response times and throughput.

About this task

You can set a user group to emulate the speed at which HTTP data is sent and received. By delaying the network uploads and downloads to emulate a slower network connection, the user group mirrors real-world interaction with production servers.

Procedure

To emulate line speed:

  1. In the Test Navigator, browse to the schedule and double-click it. The schedule opens.
  2. In the schedule, click the user group for which you want to define a line speed.
  3. In the Schedule Element Details area, click the Options tab.
  4. To declare the line speed value:
    1. Click Enable line speed control.
    2. Select the actual line speed, or select Custom values to enter a value.
    3. Select the required line speed, or select Custom values to enter a value, which must be lower than the actual line speed.

Example

If a user group employs multiple agent computers (locations) that have different real line speed values, to obtain the highest possible accuracy, we recommend that you divide the user group into smaller user groups so that each user group contains agents with the same actual line speed value. However, even if the actual line speeds are different, if they are both much larger than the required line speed, then the inaccuracy will be small, and may even be tolerable.

The following example illustrates this difference. The actual line speeds are different (100 Mbps and 10 Mbps) but are both much larger than the desired line speed of 56 Kbps:

The computed line speed delay for a 5000 byte response where the actual line speed is 100 Mbps and the desired line speed is 56 Kbps is 706 ms. The computed line speed delay for a 5000 byte response where the actual line speed is 10 Mbps and the desired line speed is 56 Kbps is 702 ms. In this example, the inaccuracy is only 4 ms.

Related tasks:
Adding a user group to a schedule
Adjusting user groups
Running long duration tests
Running a user group at a remote location
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