What is Application Load Balancer? #

Load balancing is a computer technology that distributes access requests across multiple servers during network transmission. Load balancing helps enhance the performance and reliability of services. Load balancing can be implemented at different layers of the OSI 7-layer model. In most cases, load balancing is implemented at the application layer (Layer 7) and the transport layer (Layer 4).
Application Load Balancer (ALB) is a load balancing service that works at the application layer, and supports the following protocols: HTTP, HTTPS, HTTP/2, WebSocket, WebSocket Secure, and QUIC.
ALB is designed to implement fine-grained and balanced traffic routing and eliminate the impact of single points of failure for websites, audio and video applications, and other high-traffic distribution scenarios. Therefore, ALB can enhance the overall service performance of your application system, improving both stability and reliability.

Features #

Multiple protocols #

To meet requirements in different scenarios, ALB supports multiple application layer protocols including HTTP, HTTPS, HTTP/2, WebSocket, WebSocket Secure, and QUIC.

Load balancing algorithms #

ALB supports three load balancing algorithms: Weighted Round Robin (WRR), Weighted Least Connections (WLC), and Source IP Hash (SH). These algorithms can ensure balanced traffic distribution.

Security protection #

You can enable the Web Application Firewall (WAF) protection for your ALB instances and use the access control feature to screen and restrict request sources. With these features, you can implement real-time defense against malicious request attacks.

Health check #

To maintain the stability of your backend service, ALB monitors the health status of your backend servers to detect and isolate backend servers in abnormal status in a timely manner.

Certificate management #

ALB offers the certificate management feature to allow you to upload proprietary certificates for HTTPS connections. You can also use certificates from Certificate Center. This allows you to quickly bind SSL certificates to your listeners.

Access logging #

ALB offers the logging feature to collect Layer 7 access logs. An access log includes information such as the IP address of the client and the response from the server. Access logs can help you analyze the actions of your users and facilitate precise maintenance and swift troubleshooting for your application.