This topic introduces common terms used in Alibaba Cloud Content Delivery Network (CDN).

Accelerated domain

An accelerated domain is a domain that uses Alibaba Cloud CDN to accelerate content delivery. A domain is the address of a group of servers, such as web servers, email servers, and FTP servers.

CNAME record

A canonical name (CNAME) record is an alias record used to map a domain to another domain that provides an IP address. The following example shows you how to use a CNAME record:
  1. The domain docs.example.com can be used to access the data stored on your server. However, you also want the data to be accessed by using the domain documents.example.com.
  2. You can configure a CNAME record with your Domain Name System (DNS) hosting provider to map documents.example.com to docs.example.com.
  3. Then, all requests sent to documents.example.com are redirected to docs.example.com.

CNAME

After you log on to the CDN console and create an accelerated domain, Alibaba Cloud CDN team assigns a canonical name (CNAME) to the accelerated domain. The CNAME is provided in the format of *.*kunlun*.com. You must configure a CNAME record with your DNS hosting provider to map the accelerated domain to the CNAME *.*kunlun*.com. After the CNAME record takes effect, all requests sent to the accelerated domain are redirected to a CDN node. This helps to accelerate content distribution.

DNS

Domain Name System (DNS) is used to translate domain names into IP addresses that the Internet can recognize. A dedicated DNS server is used to automatically translate domain names into IP addresses. One domain name is mapped to one IP address. For example, if you enter www.baidu.com in the address bar of your browser, the DNS server automatically translates the domain into 220.181.112.143.

SSL/TLS

Secure Sockets Layer (SSL) is a TCP-based secure communications protocol. This protocol helps to ensure the integrity and security of data when the data is transmitted over the Internet. After SSL is standardized, its name is changed to Transport Layer Security (TLS). Therefore, SSL and TLS are collectively known as SSL/TLS.

Edge node

In the documentation of Alibaba Cloud CDN, an Alibaba Cloud edge node is also referred as a CDN node, cache node, acceleration node, Alibaba Cloud node, or node. The concept of an edge node is proposed to simplify the complex network structure. Edge nodes are located near end users on the network. Therefore, compared with origin servers, edge nodes can respond to requests more efficiently. Alibaba Cloud CDN caches frequently accessed content to edge nodes to improve user experience.

Origin server

An origin server is the server where your actual workloads are running. When you create an accelerated domain, you can specify the origin server by using the domain name of your Object Storage Service (OSS) bucket, the IP address or domain name of a publicly accessible web server, or a Function Compute domain name.

Back-to-origin

When a CDN node has not cached a resource that a client requests or the cached resource has expired, a back-to-origin process is triggered. The CDN node requests the resource from the corresponding origin server and then returns the resource to the client.

For example, when a user requests a resource by using a URL, if the optimal CDN node, which is usually geographically closest to the user, has not cached the resource, the CDN node requests the resource directly from the origin server. After the CDN node receives the resource from the origin server, it returns the resource to the user.

Origin host

An origin host refers to the website domain name accessed on the origin server by a CDN node during the back-to-origin process.

Example 1: Use a domain name as the origin

If the origin is set to www.a.com and the origin host is set to www.b.com, CDN requests content from website www.b.com that is hosted on the origin server www.a.com.

Example 2: Use an IP address as the origin

If the origin is set to IP address 1.1.1.1 and the origin host is set to www.b.com, CDN requests content from the website www.b.com that is hosted on the origin server at IP address 1.1.1.1.

Origin protocol policy

The protocol policy that you want Alibaba Cloud CDN to use when retrieving content from your origin server. If you set the origin protocol policy to Follow in the Alibaba Cloud CDN console, Alibaba Cloud CDN communicates with your origin server by using HTTP or HTTPS, depending on the protocol of the request. For example, if the client sends an HTTP request, Alibaba Cloud CDN communicates with the origin server over HTTP if necessary.

Parameter filtering

Parameter filtering is a feature provided by Alibaba Cloud CDN. You can enable or disable this feature to determine whether to ignore the parameters that follow the question mark (?) in the URL of each request when Alibaba Cloud CDN caches the content from the origin server.
  • With this feature enabled, a CDN node ignores the parameters following the question mark (?) in the URL to request content from the origin server when the requested content is accessed for the first time. Then, the CDN node caches one version of the retrieved content and serves all subsequent requests for the content from the cache.
  • With this feature disabled, the CDN node creates different caches for each request with a unique URL that includes parameters.

If URLs with different parameters point to the same resource, we recommend that you enable this feature to increase the cache hit ratio.