Alibaba Cloud (SLB) has the following features:

Supported protocol

Alibaba Cloud provides both Layer-4 (TCP and UDP) and Layer-7 (HTTP and HTTPS) load balancing services.

Health check

With the health check function, SLB can automatically block abnormal ECS instances and distribute requests to them when they become normal.

Session persistence

Supports session persistence. You can set listening rules to forward a session request from a client to the same backend ECS instance during the session lifecycle.

Scheduling algorithm

SLB supports the following scheduling algorithms:

  • Round robin: Requests are distributed across the backend ECS servers sequentially.
  • Weighted round robin (WRR): You can set a weight for each backend server. Servers with higher weights receive more requests than those with lower weights.
  • Weighted least connections (WLC): In addition to weights set for backend ECS servers, the number of connections to servers is also considered. The server with a higher weight value will receive a larger percentage of live connections at any one time. If the weights are the same, the system directs network connections to the server with the smallest number of established connections.

Domain name/URL-based forwarding

For Layer-7 (HTTP and HTTPS) protocols, supports forwarding traffic to different backend servers based on domain names or URLs.

Multiple zones

Supports creating SLB instances in the specified zones. To provide a more stable and reliable load balancing service, SLB can be deployed in multiple zones in most regions. If the primary zone becomes abnormal, the backup zone automatically takes over the load balancing service from the faulty zone.

Access control

You can set a whitelist to control which IP addresses can access Server Load Balancer.


Combined with Alibaba Cloud Security, SLB can defend against up to 5 Gbps DDoS attacks.

Certificate management

A centralized certificate management service is provided for HTTPS listeners. With Certificate Management, you do not need to upload certificates to backend ECS instances. Deciphering is performed on to reduce the CPU overheads of backend ECS instances.

Bandwidth control

You can set the bandwidth peak for each listener based on the service that the application can provide.

Instance type

You can choose to create an Internet or intranet service. The system will assign a public IP address or private IP address accordingly. Depending on your business scenario, you can choose to configure a load balancing service that is exposed to the Internet or that is private to internal use.


With the Monitor function, you can get the real-time status of your Server Load Balancer.

Management methods

You can manage instances through various methods, such as the console, API, and SDK.