Server Load Balancer(SLB): Load Balancing Services at Layer 4 and Layer 7- Alibaba Cloud

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Server Load Balancer (SLB) distributes network traffic across groups of backend servers to improve the service capability and application availability. It provides functions as a reverse proxy at Layer 7（ALB）and load balancing services at Layer 4 （CLB）.

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Overview
SLB Types & Pricing
Features
Scenarios
Customers
Documentation

Overview

Overview
SLB Types & Pricing
Features
Scenarios
Customers
Documentation

Latest News

Release Notes

Application Load Balancer (ALB) is now available.

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Free Trial for Individuals

Receive a USD $15 Classic Load Balancer (CLB) credit

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Free Trial for Enterprise

Receive a USD $55 Classic Load Balancer (CLB) credit

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High Performance and Elasticity
Stable, Reliable, and Globally Available

Server Load Balancer (SLB) provides high-performance load balancing services. Classic Load Balancer (CLB) runs at Layer 4 and supports up to 100,000 QPS. 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.

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 and UDP at the network layer, and HTTP, HTTPS, QUIC, and gRPC at the application layer. ALB provides multiple advanced routing features at Layer 7.

Cloud-Native

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.

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SLB Types

Type	Application Load Balancer (ALB)	Classic Load Balancer (CLB)
Service Scope	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
Performance	Based on the NFV platform A single ALB instance supports 1,000,000 QPS	Developed on top of a physical machine architecture Supports up to 5,000,000 connections
O&M	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	Serves as a cloud native gateway to distribute and mirror network traffic and supports canary release and blue-green deployment	Supports cloud-native services
Scenarios	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
Pricing	ALB Pricing Details >	CLB Pricing Details >
Getting started	Create an ALB	Create a CLB

Features

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.

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.

Scenarios

Challenges

Workloads on backend servers are heavy during peak hours in the audio, video, and game industries:

• A large amount of network traffic is forwarded between clients and backend servers in scenarios, such as short videos, long videos, livestreaming, online education, and online games.

• Large traffic fluctuations occur in audio and video scenarios. This affects the performance, elasticity, stability, and availability of systems.

Benefits

High Performance

Supports Cloud Network Management 2.0. A single SLB instance supports 1,000,000 QPS.
High Elasticity

SLB automatically adjusts its processing capabilities based on the inbound traffic. You do not need to configure the service manually.
Advanced Protocol

Supports QUIC to facilitate transmission for videos and reduce First Contentful Paint (FCP) time.

Alibaba Cloud CDN

A highly scalable and cost-effective service to accelerate content delivery.

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Anti-DDoS

Automatically protects your service from DDoS attacks.

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ApsaraDB for Redis

A fully-managed cloud database service that supports Redis.

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Requirements

Frequent business adjustment occurs in scenarios, such as new retail, new finance, product releases, and large-scale promotions.

Services must be secure, reliable, elastic, and ready to use after they are activated.

You must provide flexible billing to reduce costs.

Benefits

Ready-to-use

You do not need to purchase or deploy any hardware. The SLB service is ready to use after it is activated. You can specify billing methods based on your business requirements. This allows you to manage your business flexibly and efficiently.
Scalability

SLB automatically adjusts its processing capabilities based on inbound traffic. You do not need to configure the service manually in large-scale promotion scenarios.
High Security and Reliability

Provides disaster recovery at four levels. SLB supports integration with Anti-DDoS and Cloud Firewall to secure your business.

Elastic Compute Service (ECS)

Provides elastic and secure servers to host your services on the cloud.

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Web Application Firewall (WAF)

Defends websites from common attacks at the application layer to ensure security and availability.

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Cloud Enterprise Network (CEN)

A global network that consists of interconnected hybrid clouds and distributed systems.

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Requirements

Enterprises from the Internet, finance, and enterprise sectors want to use advanced cloud-native technologies to deploy their new businesses on the cloud or adjust their current businesses.

You must use the cloud-native SLB service to use ACK, SAE, or Kubernetes.

Benefits

Cloud-Native

Integrated with ACK, SAE, and Kubernetes. SLB functions as a cloud-native gateway on Alibaba Cloud to distribute inbound network traffic.
Fully Developed APIs

SLB supports gRPC and provides fully-developed APIs that you can call to manage the connections to a large number of microservices.

Container Service for Kubernetes (ACK)

Provides secure and highly-available container services and supports stable upgrades.

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Elastic IP Address (EIP)

An independent public IP resource that allows flexible management.

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NAT Gateway

Functions as an Internet gateway for a VPC.

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Requirements

Multinational enterprises want to distribute network traffic from different regions across applications and connect their data centers to Alibaba Cloud in a cost-effective way.

They want to build a hybrid cloud or a cross-region network that provides multi-level disaster recovery.

Benefits

Support for All Regions

Supports intelligent DNS resolution. Client traffic is directed to the best available IP addresses to accelerate transmission and improve the user experience.
Multi-Level Disaster Recovery

SLB provides high availability across regions and zones.
Ease of Use

You can use SLB and CEN to build a global network that connects data centers in different regions to Alibaba Cloud in a fast and simplified way.

Global Accelerator (GA)

Provides network acceleration services for your Internet-facing application globally.

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Cloud Enterprise Network (CEN)

Allows you to build a global network that consists of interconnected hybrid clouds and distributed systems with scalability and communication capabilities at the enterprise level.

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Object Storage Service (OSS)

Provides encrypted and secure storage services on the cloud.

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Product Updates

More updates >

“Alibaba Cloud allows us to host our applications, databases, networks, and email servers on ECS instances. We can adjust the number of ECS instances or modify their configurations based on our business requirements.”

[LPAS] Learn More >

“Tanahmu benefits from the scalability provided by Alibaba Cloud, especially when SLB is used. SLB allows Tanahmu to handle traffic spikes at the earliest opportunity and keep CAPEX and OPEX at the lowest level.”

【TanahMu】Learn More

“SLB distributes network traffic across multiple backend servers. Only backend servers that function as expected can receive network traffic. SLB supports auto scaling based on the amount of inbound traffic. Therefore, the elasticity of applications is ensured.”

[The Gate Academy] Learn More >

“SLB distributes network traffic across multiple backend servers to avoid service interruption. This ensures efficient and seamless access for users.”

[Halosis] Learn More >

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Documentation and Tools

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API & SDK

Server Load Balancer (SLB) APIs and SDKs

Quick Start

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Server Load Balancer (SLB) FAQ

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