Alibaba Cloud CDN is a virtual network that consists of globally distributed edge nodes. Alibaba Cloud CDN reduces loads on origin servers to prevent network congestion. You can use Alibaba Cloud CDN to accelerate content delivery for websites in different regions or scenarios.

Alibaba Cloud CDN provides more than 2,800 globally distributed edge nodes. Among these nodes, more than 2,300 are distributed across 31 provincial regions in mainland China and more than 500 are distributed across over 70 countries and regions, including Hong Kong (China), Macao (China), and Taiwan (China). The total bandwidth capacity of Alibaba Cloud CDN can reach up to 150 Tbit/s.

Alibaba Cloud CDN caches resources from origin servers to the globally distributed edge nodes. Users can retrieve resources from the nearest edge nodes instead of origin servers. This accelerates content delivery and reduces loads on origin servers. Some edge nodes support IPv6.

Alibaba Cloud CDN allows you to delivery content in an efficient and simple way. You do not need to change the current service structure or complete complex configurations. You can add domain names to be accelerated after a few simple steps in the Alibaba Cloud CDN console. Alibaba Cloud CDN accelerates content delivery by using the globally distributed edge nodes. For more information about how to activate and use Alibaba Cloud CDN, see Quick Start.

Benefits

You can use Alibaba Cloud CDN to separately accelerate static and dynamic content. Alibaba Cloud CDN provides the following benefits:
  • Widely distributed nodes: Alibaba Cloud CDN redirects requests to the nearest nodes that belong to the same Internet service provider (ISP) as the clients. This accelerates long-distance content delivery and reduces network latency for cross-ISP content delivery.
  • Scalable resources: Alibaba Cloud CDN provides more than 2,800 globally distributed edge nodes to ensure resource scalability and service availability.
  • Accurate scheduling: Alibaba Cloud CDN monitors the health status of edge nodes in real time, and redirects requests to optimal nodes selected by the scheduling system based on client locations and ISPs. This improves the acceleration performance.
  • Intelligent connections: Alibaba Cloud CDN uses optimization strategies such as protocol optimization and connection optimization to reduce network latency and accelerate content delivery, especially over unstable networks.
  • Efficient caching: Alibaba Cloud CDN increases the cache hit ratio because requests can hit cache on the nearest edge nodes. This accelerates content delivery.
  • Lower IT expenses: Edge nodes provide computing, bandwidth, and connection resources. This reduces IT expenses.
  • High bandwidth capacity: The total bandwidth of Alibaba Cloud CDN can reach up to 150 Tbit/s.
  • Standardized API: The Alibaba Cloud CDN API is easy to use and supports various operations.

For more information, see Benefits.

Service architecture

The following figure shows the architecture of Alibaba Cloud CDN. Alibaba Cloud CDN consists of a scheduling system, a link quality system, a caching system, and a support system. Architecture
  • Scheduling system

    The scheduling system provides a policy center and supports Domain Name System (DNS) resolution, HTTPDNS, and 302 redirection. After a client sends a request, the request is resolved by DNS resolution and then processed by the scheduling system.

  • Link quality system

    The link quality system monitors the loads and health status of all nodes and links in real time, and reports monitoring data to the scheduling system. Then, the scheduling system selects an optimal access point for requests based on the IP address information such as the Internet service provider (ISP) and region of the requests.

  • Caching system

    The caching system redirects requests to edge nodes based on the access points of the requests. If the requested resource is already cached on the edge nodes, the resource is directly returned to the client. If the requested resource is not cached on L1 or L2 nodes, the request is redirected to the origin server to retrieve the resource. Then, the retrieved resource is returned to the client and cached on the edge nodes. Subsequent requests can directly retrieve the resource from the edge nodes. Alibaba Cloud CDN uses a multi-level cache hierarchy to accelerate content delivery, reduce the amount of bandwidth resources consumed by the back-to-origin process, and improve user experience.

  • Support system
    The support system supports Tianyan, also known as the Five-hundred-meter Aperture Spherical radio Telescope (FAST), data intelligence, and configuration management. The support system can monitor resources, analyze data, and manage configurations.
    • Resource monitoring: Tianyan can monitor the status of services that are running in the caching system. For example, Tianyan can monitor the number of queries per second (QPS), bandwidth, and HTTP status codes for a domain name that is accelerated by Alibaba Cloud CDN.
    • Data analytics: You can analyze data, such as the top N most frequently requested URLs, page views, and unique visitors for a domain name that is accelerated by Alibaba Cloud CDN.
    • Configuration management: You can create and manage cache expiration rules to improve the efficiency of the caching system. For example, you can create a cache expiration rule for a specified type of file or enable parameter filtering.

How it works

The following example shows how Alibaba Cloud CDN works.

In this example, the domain name accelerated by Alibaba Cloud CDN is www.a.com, and acceleration is enabled. The following figure shows how Alibaba Cloud CDN works after it receives an HTTP request from a client in Beijing. How it works
  1. When the client in Beijing sends a request to retrieve resources from www.a.com, a domain name resolution request is sent to the local DNS server (LDNS).
  2. The LDNS checks whether the cache contains an IP address record that corresponds to www.a.com. If so, the LDNS directly returns the IP address to the client. If not, the LDNS queries the IP address from the authoritative DNS.
  3. After the authoritative DNS resolves www.a.com, it returns the IP address of the corresponding Canonical Name (CNAME) www.a.tbcdn.com.
  4. The LDNS sends the domain name resolution request to the Alibaba Cloud DNS scheduling system. Alibaba Cloud DNS selects the IP address of an optimal node for the request.
  5. The LDNS receives the resolved IP address returned by Alibaba Cloud DNS.
  6. The client receives the resolved IP address.
  7. The client initiates a request to the received IP address.
    • If the edge node that corresponds to the IP address (the node in Beijing in this example) has cached the requested resource, the resource is directly returned to the client, as shown in steps 7 and 8 in the preceding figure. Then, the request ends.
    • If the edge node that corresponds to the IP address has not cached the resource, the edge node redirects the request to the origin server to retrieve the resource. The retrieved resource is returned to the client and cached on edge nodes (the node in Beijing in this example) based on the cache expiration rules. Then, the request ends. For more information about how to configure a cache expiration rule, see Create a cache expiration rule.

Differences between Alibaba Cloud CDN and DCDN

Item Alibaba Cloud CDN Dynamic Route for CDN (DCDN)
Typical scenarios Game updates, app updates for mobile phones, on-demand videos including long and short videos, and infographic websites. Online shops, online payments, online chatting, online education, online multiplayer games, and financial management.
Accelerated regions
  • Mainland China only
  • Global
  • Global (excluding mainland China)
  • Mainland China only
  • Global
  • Global (excluding mainland China)
Acceleration methods Accelerates the delivery of static content and redirects requests for dynamic content to origin servers. Alibaba Cloud CDN is suitable for scenarios that require high bandwidth and process a large amount of network traffic.
  • Provides more than 2,800 globally distributed edge nodes that can cache content based on cache expiration rules.
  • Balances loads on origin servers, distributes requests to origin servers based on their weights, reduces back-to-origin requests to protect origin servers, and reduces costs on origin servers.
  • Caches static content such images and videos on edge nodes to deliver content from the nearest nodes to clients.
Accelerates the delivery of dynamic content, or both dynamic and static content
  • Accelerate the delivery of dynamic content

    If content requested by some requests, such as POST requests, is not cached on edge nodes, the edge nodes redirect the requests to the origin server to retrieve content based on an intelligent scheduling system. The system selects an optimal route for redirection.

  • Accelerate the delivery of both dynamic and static content

    Intelligently identifies static and dynamic content. Static content is cached on edge nodes. Users can directly retrieve the cached static content from the nearest edge nodes. Requests for dynamic content are redirected to the origin server through an optimal route selected by the intelligent scheduling system.

Supported protocols
  • Application layer: HTTP, HTTPS, and Quick UDP Internet Connections (QUIC)
  • Network layer: IPv4 and IPv6
  • Application layer: HTTP, HTTPS, and WebSocket
  • Transport layer: TCP and UDP
  • Network layer: IPv4 and IPv6
Scheduling modes

Supports DNS resolution, HTTPDNS, and 302 redirection.

Supports DNS resolution, HTTPDNS, and 302 redirection.

Edge computing
  • Supports EdgeScript (ES). You can use scripts to customize Alibaba Cloud CDN features on edge nodes.
  • Supports image editing.
  • Supports EdgeRoutine (ER). You can use ER to deploy programs on edge nodes. For example, you can perform A/B testing and run prefetch tasks.
  • Supports EdgeScript (ES). You can use scripts to customize Alibaba Cloud CDN features on edge nodes.
  • Supports image editing.

For more information about static and dynamic content, see What are static content and dynamic content?.

Scenarios

Alibaba Cloud CDN can accelerate content delivery for media websites, purpose-specific websites, and resource distribution websites. The following table describes the scenarios of each type of website.
Media website Purpose-specific website Resource distribution website
  • Music websites
  • Video websites
  • News websites
  • Online education websites
  • E-commence websites
  • Corporate websites
  • Infographic websites
  • Financial markets
  • Web portals
  • Social media platforms
  • app stores
  • Game stores
  • System over-the-air (OTA) updates
  • File distribution

For more information, see Scenarios.

Pricing

Alibaba Cloud CDN is billed for basic services and value-added services.
  • Billing of basic services: supports the pay-by-data-transfer and pay-by-peak-bandwidth metering methods. The default metering method is pay-by-data-transfer. For more information, see Billing of basic services.
  • Billing of value-added services: The billable items include HTTPS requests for static content, QUIC requests for static content, and real-time log entries. For more information, see Billing of value-added services.

For more information, see CDN Pricing.

We recommend that you familiarize yourself with the billing rules of Alibaba Cloud CDN before you activate Alibaba Cloud CDN. For more information, see Activate Alibaba Cloud CDN.

Management tools

An Alibaba Cloud account allows you to manage Alibaba Cloud CDN anywhere by using the following methods:
  • Alibaba Cloud CDN console

    The Alibaba Cloud CDN console is an easy-to-use web console that supports interactive operations. For more information, see Features and Overview.

  • Alibaba Cloud CDN API

    The Alibaba Cloud CDN API is a remote procedure call (RPC) API that supports GET and POST requests. For more information, see API Reference.

References

Alibaba Cloud CDN can be used to accelerate the delivery of content in Object Storage Service (OSS) buckets or on Elastic Compute Service (ECS) instances. The following topics describe the best practices:

Service bundling

The following table describes the related services of Alibaba Cloud CDN to help you understand the position and use of Alibaba Cloud CDN among other Alibaba Cloud services.
Service Benefit
DCDN DCDN separates dynamic content from static content, and accelerates the delivery of both static and dynamic content.
OSS If you use an OSS bucket as an origin server, you can use Alibaba Cloud CDN to accelerate content delivery and reduce Internet data transfer fees.
ApsaraVideo Live You can use Alibaba Cloud CDN together with ApsaraVideo Live to achieve media feed storage, video segmentation and transcoding, access authentication, and content delivery acceleration.
ApsaraVideo VOD (VOD) You can use Alibaba Cloud CDN together with VOD to reduce the buffer time and improve playback smoothness.
Alibaba Cloud DNS You can use Alibaba Cloud DNS that is highly available and stable to ensure smooth access to resources.
ECS You can use Alibaba Cloud CDN together with ECS to improve website availability, protect information about origin servers, and minimize bandwidth usage costs.
Server Load Balancer (SLB) You can specify the IP address of an SLB instance as the origin address to balance loads during the back-to-origin process.