About Bandwidth Control

Bandwidth Control allows you to preserve access to your business-critical applications regardless of your internet pipe consumption. This enables you to things like adding more restrictive rules around social media and streaming media. For example, you can allocate a maximum of 10% of the bandwidth to the Streaming Media, Social Media, and File Share bandwidth class bandwidth classes.  When bandwidth is restricted, these classes are not guaranteed any bandwidth and are restricted to 10% of the bandwidth when it is available.

Bandwidth Control at Two Levels

Zscaler provides bandwidth control at two levels.

  • At the first level, the Zscaler service provides bandwidth control by location. You can configure maximum upload and download bandwidth limits for each location in your organization. These limits apply to the traffic that is proxied to Zscaler for bandwidth control.

    Further, you can also control bandwidth management by sub-location. This provides admins with the versatility of configuring different policies for different sub-locations. Different sub-locations can use bandwidth from the location or, if desired, sub-locations can have a specific bandwidth limit enforced. Enforcing limits is particularly useful for guest Wi-Fi networks.

The service applies bandwidth controls to traffic from known locations only; that is, locations that are configured on the Zscaler Admin Portal. The Bandwidth Control policy does not apply to remote users because their traffic does not come from a configured location and their source IP address has unknown upload and download bandwidth values.

  • At the second level, for each location, you can configure bandwidth shaping rules based on bandwidth classes, such as VoIP or Web Conferencing, URL categories, or custom application classes that you define. The Zscaler bandwidth algorithm allows an application class full bandwidth utilization until there is contention for the bandwidth by a traffic class with a higher priority. When application classes compete for bandwidth, the service takes action based on the multiple QoS controls that you configured in the bandwidth control policy, as shown below:

Diagram of how Zscaler service acts based on QoS controls configured in Bandwidth Control policy

The Zscaler service rebalances the bandwidth in real time and buffers packets for application classes that hit the bandwidth quota limit during one second intervals. This behavior ensures that business-critical applications run at full speed, with no deterioration in quality. The Zscaler service applies the policy to all HTTP and HTTPS traffic from the location. You do not need to enable SSL interception because it works at the TCP level.

How Bandwidth Control Works

First, you specify the maximum upload and download bandwidth limits for each location in your organization. About 5% of TCP traffic is overhead, such as packet headers. The Zscaler service does not include these in its bandwidth calculations. It only includes the application traffic.

Next, you define your bandwidth classes, specifying what URL categories and applications belong to a given bandwidth class. You can then reference those bandwidth classes in your bandwidth control policy − a set of prioritized rules that tell the service how to allocate the bandwidth when contention occurs. Each rule defines a maximum and minimum bandwidth for the bandwidth classes in the rule along with other parameters, like location and time of day.

Based on the bandwidth policy, Zscaler will distribute the bandwidth to each rule from top to bottom by looking at the minimum bandwidth first. Once completed, it will pass through each rule a second time to allocate the remaining bandwidth and distribute it based on the maximum bandwidth configuration.

The maximum bandwidth specifies the maximum percentage of the total bandwidth that the configured bandwidth class can use at a given point in time, and the minimum bandwidth specifies the guaranteed minimum bandwidth percentage that is available for the bandwidth class.

The maximum bandwidth percentage is applied at all times. Because of this, traffic can only take up to the percentage specified of the location's bandwidth, whether or not there is any congestion. This is useful to users who wish to suppress, but not block, non-business traffic.

The minimum bandwidth percentage is only enforced when there is contention on a location's connection and when traffic from the specified bandwidth classes is present. This allows a bandwidth class full bandwidth utilization until there is contention for the bandwidth by a traffic class with a higher priority. When bandwidth classes compete for bandwidth, the service allocates the guaranteed minimum bandwidth percentages to the bandwidth classes and allocates the remaining bandwidth according to the prioritized rules. Therefore the total minimum bandwidth must be less than 100%. 

To see a sample policy for bandwidth management, see Bandwidth Control Policy Example.

You can go to the Bandwidth Control dashboard to view your organization's bandwidth usage in real time. You can also go to Analytics > Interactive Reports to view the standard reports for Bandwidth Control or to create custom reports as well.

To see how this policy fits into the overall order of policy enforcement, see How does the Zscaler service enforce policies?

On the Bandwidth Control page, you can do the following:

  1. View the Zscaler Recommended Policy for Bandwidth Control
  2. Configure a Bandwidth Control policy rule
  3. View a list of all configured Bandwidth Control policy rules
  4. Search for a configured Bandwidth Control policy rule
  5. Edit the Bandwidth Control policy rule
  6. Duplicate the Bandwidth Control policy rule
  7. Modify the table and its columns

Screenshot of the Zscaler Bandwidth Control page and tasks