QoS policy rules

You can create two rule types to define a QoS policy: bandwidth limit and minimum bandwidth.

Bandwidth limit

Provides bandwidth limitations on networks, ports or floating IPs. Any VM traffic that exceeds the specified rate will be dropped.

To define a bandwidth limit, specify the following parameters:

• max_kbps: The maximum rate, in Kbps, that the VM can send.

• max_burst_kbps: The maximum amount of data, in kbits, that the port can send in a VM if the token buffer is full. The token buffer replenishes at a max_kbps rate.

  • If the burst value is set too low, bandwidth usage will be throttled even with a proper bandwidth limit setting, resulting in a lower than expected bandwidth.
  • If the configured burst value is too high, too few packets could be limited, resulting in a higher than expected bandwidth limit.

  If you omit this parameter, the recommended burst value for TCP traffic will be applied, which defaults to 80% of the bandwidth limit. For example, if the bandwidth limit is 1000 kbps, then a burst value of 800 kbps is enough.

• ingress or egress: The direction of traffic the rule is applied to. For a VM, ingress indicates download, and egress indicates upload.

Minimum bandwidth

Provides minimum bandwidth guarantees on networks, ports or floating IPs. VM traffic will use no less than the specified bandwidth.

To define minimum bandwidth, specify the following parameters:

• min-kbps: The minimum bandwidth, in Kbps, guaranteed to a VM.
• ingress or egress: The direction of traffic the rule is applied to. For a VM, ingress indicates download, and egress indicates upload.

Rules of different types can be combined in one QoS policy. For example, you can create a bandwidth limit rule and a minimum bandwidth rule. Additionally, you can add rules of one type to a policy if the traffic direction of each rule is different. For example, you can create two bandwidth limit rules, one for egress traffic and one for ingress traffic.