Server Load Balancer


Server Load Balancer (SLB) distributes network traffic across groups of backend servers to improve the service capability and application availability. It Includes Layer 4 Network Load Balancer (NLB), Layer 7 Application Load Balancer (ALB), and Classic Load Balancer (CLB). It Is the Official Cloud-Native Gateway of Alibaba Cloud.

Server Load Balancer (SLB) provides high-performance load balancing services. with super four-seven processing capabilities.Network Load Balancer (NLB) Provides powerful processing capabilities at Layer 7,A single NLB instance supports 100 million concurrent connections. The newly released Application Load Balancer (ALB) service is based on Alibaba Cloud Apsara Network 2.0 and supports up to 1,000,000 QPS.

The Server Load Balancer (SLB) instances feature high performance and support auto scaling. They can automatically adjust resources based on your business requirements to simplify O&M.


Explore: Alibaba Cloud ECS pricing

High Security and Reliability

Server Load Balancer (SLB) provides disaster recovery at four levels for high availability. CLB and ALB support built-in Anti-DDoS services to ensure business security. In addition, you can integrate ALB with WAF in the console to ensure security at the application layer.

Multiple Protocols

Server Load Balancer (SLB) supports multiple protocols, such as TCP, UDP and TCPSSL at the network layer, and HTTP, HTTPS, QUIC, and gRPC at the application layer. NLB provides large-scale SSL offloading capabilities,ALB provides multiple advanced routing features at Layer 7.


ALB and CLB support cloud-native networks. ALB is integrated with other cloud-native services, such as Container Service for Kubernetes (ACK), Serverless App Engine (SAE), and Kubernetes, and functions as a cloud-native gateway to distribute inbound network traffic.


TypeNetwork Load Balancer (NLB)Application Load Balancer (ALB)Classic Load Balancer (CLB)
Service Scope
  • Provides powerful processing capabilities at Layer 4 and large-scale SSL offloading capabilities
  • Intended for TCP, UDP and SSL over TCP
  • Focuses on network delivery
  • Provides powerful processing capabilities at Layer 7 and multiple advanced routing features
  • Supports HTTP, HTTPS, and QUIC at Layer 7
  • Focuses on application delivery
  • Provides powerful processing capabilities for Layer 4 load balancing
    Supports protocols such as TCP, UDP, HTTP, and HTTPS
    Focuses on network delivery
  • Based on the NFV platform and auto scaling
  • A single NLB instance supports 100 million concurrent connections
  • Based on the NFV platform and auto scaling
  • A single ALB instance supports 1,000,000 QPS
  • Developed on top of a physical machine architecture
  • Supports up to 5,000,000 connections
Operations & Maintenance
  • Supports auto scaling to adjust processing capabilities based on inbound traffic
  • Supports auto scaling to adjust processing capabilities based on inbound traffic
  • Provides multiple specifications that you can specify based on the traffic peaks in your business
Cloud-Native Support
  • Supports cloud-native services
  • Serves as a cloud native gateway to distribute and mirror network traffic and supports canary release and blue-green deployment
  • Supports cloud-native services
  • Supports high concurrency to withstand Layer 4 traffic spikes
    Serves as an ingress for IoT services such as Internet of vehicles (IoV)
  • Supports cross-zone disaster recovery and serves as an ingress for both on-premises and cloud services
  • Provides high-performance services and supports auto scaling at Layer 7
  • Maintains low network latency for audio and video applications that handle a large amount of network traffic
  • Supports canary release and blue-green deployment for cloud native applications
  • Distributes network traffic across backend servers at Layer 4 to ensure the high availability of websites and systems
  • Supports a large number of concurrent connections to backend servers
  • Provides intra-region and cross-region disaster recovery


Multiple Protocols

Supports multiple protocols to meet your business requirements in various scenarios.

  • Basic Protocols: Supports Layer 4 load balancing over TCP or UDP and Layer 7 loading balancing over HTTP or HTTPS
  • Advanced Protocols: Supports QUIC at the application layer. QUIC is an advanced protocol that improves transmission on audio, video, and mobile applications. ALB also supports gRPC, which facilitates efficient communication among microservices through API operations.
Server Load Balancer

Multi-Level Disaster Recovery
Provides disaster recovery at multiple levels to ensure high availability.

  • Health Checks: Monitors the condition of backend servers regularly. SLB does not distribute network traffic to unhealthy backend servers to ensure availability.
  • Multi-Zone Deployment: Supports multi-zone deployment in specific regions to provide zone-disaster recovery.
  • Cluster Deployment and Session Synchronization: Server Load Balancer (SLB) supports cluster deployment and session synchronization. You can perform hot upgrades and monitor the health and performance of machines in real-time.
Secure and Reliable

Provides built-in security capabilities (free of charge) to secure transmission and reduce costs.

  • Layer 4 Security: Server Load Balancer (SLB) is resilient against DDoS, SYN flood, UDP flood, ACK flood, ICMP flood, and DNS flood attacks at Layer 4.
  • Layer 7 Security: Provides security capabilities at Layer 4 and Layer 7. Layer 7 supports the configuration read-only mode. You can integrate Server Load Balancer (SLB) with WAF to secure your applications.
  • Certificate Management: Provides certificate management for HTTPS requests to ensure the reliability and security of the transmission.
Flexible Scheduling
Supports multiple scheduling algorithms and forwarding methods to improve the application deployment flexibility.

  • Scheduling Algorithms: Supports Weighted Round Robin (WRR) and Weighted Least Connection (WLC). You can specify scheduling algorithms to distribute network traffic based on your business requirements.
  • Domain Name and URL Forwarding: Distributes network traffic across backend servers based on domain names and URLs. This improves the application deployment flexibility
Flexible Management and Billing
Allows you to specify the instance type and billing method based on your business requirements. Alibaba Cloud also provides multiple methods to manage your Server Load Balancer (SLB) service.

  • Flexible Billing: Supports the pay-as-you-go and subscription billing methods and the pay-by-data-transfer and pay-by-bandwidth metering methods.
  • Flexible Management: You can create, configure, and manage Server Load Balancer (SLB) instances in the console by calling APIs in OpenAPI or using Alibaba Cloud SDKs.


In 2021, VinaHost Co., Ltd. became an Official partner of Alibaba Cloud, providing Cloud Based Services. VinaHost joins Alibaba Cloud Partner Network in order to provide individuals, organizations and businesses with high quality services with higher scalability, resilience, efficiency and innovation.

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