1. How is SLB billed?

For more information, see Billing method.

2. Is the inbound traffic of SLB billed?

No. Only the outbound traffic of SLB is billed. For more information, see Network traffic flow.

3. Is the traffic generated by health check billed?

No. The traffic generated by health checks of SLB is not included in the billed traffic.

4. Does the billing of an ECS instance change after the ECS instance is added to the backend server pool of SLB?

No. The billing of an ECS instance does not change whether you associate the ECS instance with an SLB instance. SLB and ECS instances are billed separately based on traffic.

5. Is attack traffic billed?

Yes. SLB can work with Alibaba Cloud Security to protect your SLB instances and thus minimize the billed traffic caused by malicious attacks. A latency of several seconds may happen from the time when the attack traffic reaches the scrubbing or blackholing threshold to the time when Alibaba Cloud Security starts scrubbing or blackholing. During this period, responses may be sent to attacks and this will incur fees. Such attacks also consume the bandwidth resources of SLB instances.

6. If all backend ECS instances of an SLB instance are stopped or removed, will the SLB instance continue to be billed?

Yes. Fees are charged for the following reasons:

  • Pay-by-traffic

    In the case of pay-by-traffic, no traffic fee is incurred when an SLB instance is stopped, released, or not accessed.

    SLB is a traffic distribution and control service in front of backend ECS instances and provides services by using its service address. If all backend ECS instances are stopped, but the SLB instance is not stopped, inbound traffic can still reach the service address of the SLB instance. In this case, the SLB instance will respond if it discovers that no backend ECS instances are available after health checks are performed.

    For Layer-4 SLB, only three-way handshake packets are returned. For Layer-7 SLB, a Tengine 503 error page is prompted because the service is provided by Tengine. If requests keep reaching SLB, SLB will respond continuously. The response traffic is billed.

    This also applies to SLB instances with no ECS instances added. Therefore, we recommend that you stop the SLB instance if you no longer need it.

7. Is a specification fee charged for an internal SLB instance?

  • If the internal SLB instance is a shared-performance instance, no specification fee is charged.
  • If the internal SLB instance is a guaranteed-performance instance, a specification fee is charged.

    The calculation method of specification fees for internal SLB instances is the same as that for Internet SLB instances. No instance fee or traffic fee is charged for internal SLB instances.

8. Are the traffic fees and instance fees charged for guaranteed-performance instances the same as those charged for shared-performance instances?

Yes.

9. Is an extra fee included for shared-performance instances after Alibaba Cloud starts charging for the specification fee?

No.

Extra fees are not charged for shared-performance instances unless you change them to guaranteed-performance instances.

10. Why is the monitoring data of SLB instances different from the data recorded on my bills?

  • Take traffic data as an example. The monitoring data displayed in the SLB console are average values. SLB collects monitoring data at one minute intervals and reports the data to Cloud Monitor, which then calculates the average value at 15 minute intervals. However, the data reported on your bills are accumulated values. Specifically, SLB collects traffic data at one minute intervals, and reports the accumulated values at one hour intervals to the billing system.

    The billing data reported to the billing system is accumulated values calculated at one hour intervals, whereas the monitoring data displayed in the console is of average values calculated at 15 minute interval. The different intervals used in the two calculations result in a discrepancy in monitoring data and billing data.

  • Monitoring data and billing data have different latency requirements. SLB provides real-time monitoring data. However, a short delay may occur during data collection, calculation, and display. Such a delay can cause a discrepancy between monitoring and billing data. Billing data can be recorded after a maximum delay of three hours. For example, billing data generated between 01:00-02:00 is normally reported to the billing system before 03:00, but due to a delay, may be reported to the billing system at 05:00. This results in a discrepancy between billing data and monitoring data.
  • Monitoring data and billing data have different purposes. Specifically, the purpose of monitoring is to help you observe if instances are running normally. If the instances are running abnormally, you can take measures to resolve problems in a timely manner. The purpose of billing data is to generate bills based on the actual usage of resources by your account.

11. Why is the value of the traffic actually used by HTTPS greater than the value recorded on my bills?

Some traffic is generated due to handshakes in HTTPS transactions. Therefore, the actual traffic value is higher than the value recorded on your bills.