Billing and procedure - Web Application Firewall - Alibaba Cloud Documentation Center

Web Application Firewall (WAF) provides an intelligent load balancing feature. This feature uses multi-node intelligent access technology to enable automatic scheduling and disaster recovery across multiple nodes and lines. This ensures high availability and faster access to your services.

Use cases

The intelligent load balancing feature helps you achieve high reliability with automatic network and service disaster recovery. It also provides low-latency access. This feature is ideal for the following scenarios:

Active geo-redundancy services: Multi-node services are deployed in the cloud or in data centers across multiple regions. All nodes are active simultaneously to provide services and serve as backups for disaster recovery. These services require high reliability and low-latency access.
Co-location multi-active services: Multi-node services are deployed in the cloud or in data centers within the same region. All nodes are active simultaneously to provide services and serve as backups for disaster recovery. These services require high reliability.
Co-location single-active services: A single-node service is deployed in the cloud or in a data center within the same region. This service is always online and requires high reliability.
Note
By default, co-location single-active services do not support automatic disaster recovery. However, you can use intelligent load balancing to achieve high reliability through automatic network disaster recovery.

How it works

After you enable intelligent load balancing, your WAF instance is assigned at least three protection nodes in different regions to provide automatic, multi-node disaster recovery. The feature uses intelligent DNS resolution and a Least-time back-to-origin algorithm to ensure the lowest latency for traffic from the protection node to your origin server.

Note

After you enable intelligent load balancing for a WAF instance in the Chinese mainland, a protection node is assigned in each of the following regions for disaster recovery: China (Beijing), China (Hangzhou), and China (Shenzhen).
After you enable intelligent load balancing for a WAF instance outside the Chinese mainland, multiple protection nodes are assigned in major geographical areas, such as North America, Europe, and Southeast Asia, to provide disaster recovery.

Enabling intelligent load balancing provides your WAF instance with the following capabilities.

Feature	Disabled	Enabled
Disaster recovery	Access protection based on multiple single-active nodes Centralized failover	Access protection based on multi-node load balancing Automatic network failover based on intelligent DNS resolution
Access acceleration	Not available	Optimizes the shortest path by using nearest-node access and back-to-origin routing.

Benefits

Intelligent load balancing provides the following benefits for each use case.

Use case	Benefit	Diagram
Active geo-redundancy services	Provides robust, automatic multi-line disaster recovery. Distributed health checks enable multi-line load balancing. The enhanced Least-time back-to-origin algorithm provides the lowest-latency path.
Co-location multi-active services	Provides robust, automatic multi-line disaster recovery. Distributed health checks enable multi-line load balancing.
Co-location single-active services	Provides robust, automatic multi-line disaster recovery. Distributed health checks enable multi-line load balancing.

Billing

The intelligent load balancing feature is an add-on that you must purchase separately for your WAF instance.

Pricing for the intelligent load balancing feature is based on the service duration of your WAF instance:

Instances in the Chinese mainland: USD 180/month
Instances outside the Chinese mainland: USD 800/month

Procedure

Follow these steps to use intelligent load balancing:

Enable intelligent load balancing for your WAF instance.
You can enable Intelligent Load Balancing when you purchase a WAF instance. You can also enable Intelligent Load Balancing for an existing instance by upgrading it. For more information, see Upgrade a WAF instance.
Important
For WAF instances in regions outside the Chinese mainland, intelligent load balancing is available only for the Business and Enterprise editions.
Add your website to WAF in CNAME record mode. In the Enter Your Website Information step, add all your origin server addresses to the Origin Server Address field and select Least time as the Load Balancing Algorithm. Configure other settings as needed. For more information, see Add a domain name.
Modify the DNS record for your domain name to point to the CNAME provided by WAF. This directs your website traffic through WAF for protection. For more information, see Modify a DNS record.

After you complete these steps, your WAF instance automatically uses intelligent DNS resolution and the Least-time back-to-origin algorithm to process web requests, ensuring the lowest latency for traffic from the protection nodes to your origin servers.

Important

If you use an A record to map your new domain name to the WAF virtual IP address (VIP), your web services may become inaccessible when you enable or disable intelligent load balancing.