This topic provides answers to some frequently asked questions about Classic Load Balancer (CLB).

How are Classic Load Balancer instances billed?

CLB instances support the pay-as-you-go billing method. For more information, see Pay-as-you-go.

Am I charged for inbound traffic of Classic Load Balancer?

No, you are charged for only outbound traffic of Classic Load Balancer. For more information about network traffic flows of Classic Load Balancer, see Network traffic flow.

Am I charged for traffic generated during health checks?

No, you are not charged for traffic generated during health checks on Classic Load Balancer instances.

Does the billing of an Elastic Compute Service (ECS) instance change if I add it to the backend server pool of a Classic Load Balancer instance?

No, the billing of an ECS instance does not change after you add the ECS instance to a Classic Load Balancer instance as a Classic Load Balancer backend server. Classic Load Balancer and ECS instances are separately billed based on traffic.

Am I charged for traffic generated by attacks?

Yes. Classic Load Balancer can work with Alibaba Cloud Security to protect your CLB instances. When attack traffic reaches the scrubbing or blackholing threshold, it can take several seconds for Alibaba Cloud Security to start 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 CLB instances.

If all backend ECS instances of a Classic Load Balancer instance are stopped or removed, am I still charged for the CLB instance?

You are still charged for the Classic Load Balancer instance in the following manner:

  • Pay-by-traffic

    For a pay-by-traffic CLB instance, no traffic fee is incurred when the CLB instance is stopped, released, or not accessed.

    Classic Load Balancer is a traffic distribution and control service that is used by backend ECS instances and provides services based on the service address of an CLB instance. If all backend ECS instances of a Classic Load Balancer instance are stopped, but the Classic Load Balancer instance is not stopped, inbound traffic can still reach the service address of the Classic Load Balancer instance. In this case, the Classic Load Balancer instance will respond if it discovers that no backend ECS instances are available after health checks are performed.

    For Layer 4 CLB, only three-way handshake packets are returned. For Layer 7 CLB, a Tengine 503 error page is prompted because the service is provided by Tengine. If requests keep reaching CLB, CLB keeps responding to incoming requests. You are charged for traffic generated by responses.

    This also applies to CLB instances that have no ECS instances attached. Therefore, we recommend that you stop a Classic Load Balancer instance if you no longer need the Classic Load Balancer instance.

Am I charged a specification fee if I use an internal-facing Classic Load Balancer instance?

  • If the internal-facing CLB instance is a shared-resource instance, you are not charged a specification fee.
  • If the internal-facing CLB instance is a high-performance CLB instance, you are charged a specification fee.

    You are charged specification fees for using internal-facing CLB instances in the same manner you are charged for using Internet-facing CLB instances. You are not charged instance fees or data transfer fees for using internal-facing CLB instances.

Am I charged traffic fees and instance fees for using high-performance CLB instances in the same manner as I am charged for using shared-resource CLB instances?

Yes.

Am I charged specification fees for using existing shared-resource CLB instances?

No,

you are not charged specification fees if you do not change existing shared-resource CLB instances to high-performance CLB instances.

However, if you change existing shared-resource CLB instances to high-performance CLB instances, you are charged specification fees.

Why is the monitoring data of Classic Load Balancer different from the data on the bills?

  • Take traffic data as an example. The monitoring values displayed in the Classic Load Balancer console are average values. Classic Load Balancer collects monitoring data at 1-minute intervals and reports the data to CloudMonitor, which then calculates average values at 15-minute intervals. However, the values on your bills are accumulated values. Classic Load Balancer collects traffic data at 1-minute intervals, and reports the accumulated values at 1-hour intervals to the billing system.

    The values reported to the billing system are accumulated values of data collected at 1-minute intervals, whereas the monitoring values are accumulated values of average values calculated at 15-minute intervals. The different intervals used in the two calculations result in a discrepancy between monitoring data and billing data.

  • CLB makes the best efforts to provide real-time data. However, a delay can occur during data collection and reporting by Classic Load Balancer, calculation of average values by CloudMonitor, and display of data in the console. The delay is short, but causes a discrepancy between monitoring data and billing data. Billing data can be recorded after a maximum delay of three hours. For example, billing data generated between 01:00 to 02:00 is normally reported to the billing system before 03:00, but may be reported to the billing system at 05:00 due to a delay. Different time-based requirements for data cause billing data and monitoring data to be different.
  • Monitoring data and billing data are used for different purposes. The purpose of monitoring data is to help you observe whether instances run as expected. If the instances do not run as expected, 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.

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

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