CDN:Quick start with Alibaba Cloud CDN

When you enter a URL in a browser, almost instantly, a web page, image, video, or audio file appears on your screen. Actually, this process involves a complex series of software and hardware parsing and forwarding operations. The following part breaks down a simple example request to demonstrate how Alibaba Cloud CDN accelerates content delivery.

1. Common request process

A client visits the www.example.com domain to access an image. The browser cannot directly resolve the IP address of the server that hosts the image from the domain name. In this case, the browser first queries a DNS server to obtain the IP address 10.10.10.1 that is mapped to the domain name. Then, the browser uses the IP address to locate the server and fetches the required image.

2. Request process with Alibaba Cloud CDN

As the number of requests destined for images by using www.example.com increases, the server may respond increasingly slowly due to factors such as the server configuration and network environment. This is where Alibaba Cloud CDN comes in. It provides an effective solution to accelerate response times.

Alibaba Cloud CDN works as a cache system that sits between the server and client in the network topology. When a client initiates a request to Alibaba Cloud CDN, the system first checks whether the requested image is cached. If it is, the cached image is directly returned to the browser. If not, Alibaba Cloud CDN requests the image from the server, caches it, and then sends the response to the client who initiated the request.

1. Log on to the Alibaba Cloud CDN console and navigate to the Domain Names page, find the domain name that you added, and copy the CNAME of the domain name.

   

2. Add a CNAME record to the DNS settings of the domain name. The procedure to add a CNAME record varies with your DNS provider. In this topic, Alibaba Cloud and Tencent Cloud are used as examples.

   Alibaba Cloud

   If your DNS provider is Alibaba Cloud, perform the following steps to add a CNAME record for the domain:

   1. Log on to the Alibaba Cloud DNS console by using the Alibaba Cloud account to which the domain name belongs.

   2. On the DNS resolution page, find the root domain example.com and click DNS Settings in the Actions column.

   3. Click Add DNS Record to add a record.

      

   Important

   • Hostname is the prefix of a domain name. For example, the hostname of www.example.com is www. If the domain name that you want to accelerate is the root domain example.com, enter @ in the Hostname field.

   • A CNAME record cannot share the same hostname with an A record.

   • If the domain that you want to accelerate has an A record with the same hostname, you must suspend or delete the A record before you configure a CNAME record.

   • This will cause the domain to be temporarily inaccessible. To reduce the impact on your domain, we recommend that you configure a CNAME record during off-peak hours.

   1. Click OK.

   Tencent Cloud

   If your DNS provider is Tencent Cloud, perform the following steps to add a CNAME record for the domain:

   1. Log on to the DNSPod console.

   2. On the DNSPod page, click Add Records to add a CNAME record.

      Parameter	Description	Example
      Hostname	For subdomains, enter the prefix of the subdomain. For wildcard domains, enter *. For root domains, enter @. Note For more information about subdomains, see Terms.	Subdomains: If the domain name to be accelerated is example.aliyundoc.com, enter example. If the domain name to be accelerated is www.example.aliyundoc.com, enter www.example. Wildcard domains: If the domain name to be accelerated is .aliyundoc.com, enter *. If the domain name to be accelerated is *.example.aliyundoc.com, enter *.example. Root domains: If the root domain is aliyundoc.com and the domain name to be accelerated is aliyundoc.com, enter @. Note Domain name resolution settings apply to the domain name that you register, such as aliyundoc.com, or the left part of the domain name. When you specify the Hostname parameter, enter the part to be resolved. For example, if the domain name to be accelerated is example.aliyundoc.com, enter example.
      Record Type	Select CNAME.	CNAME
      DNS Request Source	Select Default from the drop-down list.	We recommend that you keep the default setting.
      Record Value	Enter the CNAME of the domain name. Note For example, example.aliyundoc.com, and www.example.aliyundoc.com correspond to different CNAMEs. If you want to accelerate a subdomain, add the second-level domain to Alibaba Cloud CDN. Alibaba Cloud then assigns a CNAME to the subdomain. Alternatively, you can add a wildcard domain name to Alibaba Cloud CDN. Subdomains that match the wildcard domain name are mapped to the CNAME of the wildcard domain name. For more information, see Add a domain name.	www.example.com.w.kunlunsl.com
      Weight	You do not need to set this parameter.	N/A
      MX	You do not need to set this parameter.	N/A
      TTL	Enter a TTL value for the CNAME record. A smaller value indicates that the record is updated quicker.	We recommend that you keep the default setting.

   3. Click OK.

3. Verify that the configured CNAME takes effect.

   Use the Alibaba Cloud CDN console

   1. Log on to the Alibaba Cloud CDN console and navigate to the Domain Names page.

   2. Find the domain name and move the pointer over the CNAME Status column. If the status is Configured, the CNAME has taken effect.

      

   Note

   • The CNAME Status may remain Pending Configuration after your configuration. Refresh the page or check the status 5 minutes later.

   Use the nslookup command

   1. Start Command Prompt in Windows or Terminal in macOS or Linux.

   2. Enter nslookup -type=CNAME domainName (example: nslookup -type CNAME www.example.com). If the returned result is the same as the CNAME of the domain name in the Alibaba Cloud CDN console, the CNAME has taken effect.

      

1. Log on to the Alibaba Cloud CDN console.

2. In the left-side navigation pane, click Domain Names.

3. On the Domain Names page, find the domain name that you want to manage and click Manage in the Actions column.

4. In the left-side navigation tree of the domain name, click HTTPS.

5. In the HTTPS Certificate section, click Modify.

6. In the Modify HTTPS Settings dialog box, turn on HTTPS Secure Acceleration, and configure other relevant parameters.

   

   Note

   • If you have purchased a certificate from Alibaba Cloud Certificate Management Service, set the Certificate Source parameter to SSL Certificates Service and select the purchased certificate from the Certificate Name drop-down list.

   • If you use a certificate that is issued by a third-party CA, set the Certificate Source parameter to Custom Certificate (Certificate+Private Key). After you configure the Certificate Name parameter, configure the Certificate (Public Key) and Private Key parameters. Then the certificate is saved in Alibaba Cloud Certificate Management Service. You can check the certificate on the SSL Certificates page.

7. Verify that the HTTPS configuration takes effect.

   After you upload an SSL certificate, the certificate takes effect within 1 minute. To check whether the SSL certificate takes effect, you can send HTTPS requests to access resources. If the URL is displayed with an HTTPS icon in the address bar of the browser, such as Google Chrome, HTTPS acceleration is working as expected. After you configure an SSL certificate, take note of the expiration time of the certificate. You need to configure a new certificate before the certificate expires.

   

   Note

   • For more information about how to configure an SSL certificate, see Configure an SSL certificate.

1. Enable log monitoring

   Alibaba Cloud CDN supports offline logs and real-time logs. By analyzing the collected logs, you can quickly identify business and security issues and make prompt adjustments. For more information about logs, see Logs and reports.

   Log category	Log delay	Billing	Best practice
   Offline logs	Within 24 hours	Free of charge	Analyze offline logs
   Real-time logs	Within 3 minutes	Charged (Billing rules)	Best practices for shipping and analyzing Alibaba Cloud CDN real-time logs in Simple Log Service

2. Configure a Referer whitelist or blacklist

   Referer-based hotlink protection refers to access control based on the Referer header. You can configure a Referer whitelist or blacklist to control access, protecting your resources from unauthorized access.

   You can configure a Referer whitelist to allow only requests from specific domains, such as domains that are related to your website system. This way, you can identify and filter visitors to prevent unauthorized use of website resources. For more information, see Configure a Referer whitelist or blacklist to enable hotlink protection.

3. Configure real-time bandwidth monitoring

   You can use CloudMonitor to monitor the peak bandwidth of CDN domains in real time. When the bandwidth of a domain reaches the specified threshold, you will be notified of the potential risks by text message, email, or DingTalk message. For more information, see Configure alert rules.

4. Configure high bill alerts

   You can use the following features to monitor and limit expenses. To configure the features, move the pointer over Expenses in the top navigation bar of the console and select Expenses and Costs.

   • High bill alerts: If you enable this feature, the system sends an alert by text message when a daily bill exceeds the alert threshold that you specified.

   • Service suspension protection: If you disable this feature, the service immediately stops running after a payment becomes overdue to prevent high overdue payments.

   • High bill alerts: After this feature is enabled, notifications are sent to you by text message if a daily bill reaches a specified amount.

   Note

   To ensure the integrity of statistics and accuracy of bills, Alibaba Cloud CDN issues a bill about 3 hours after a billing cycle ends. Therefore, the time when fees are deducted from your account balance may be later than the time when the resources are consumed within the billing cycle. As a result, the consumption details of resources are not provided in the bill. This is a common practice among most CDN vendors.

The following content introduces more security policies.

1. Cache TTL and request parameter ignoring

   In most cases, slow content delivery is related to low cache hit ratios. We recommend that you specify a proper cache TTL and configure query parameter ignoring to increase the cache hit ratio.

   Scenario	Description	Reference
   Low cache hit ratio and slow content retrieval	The time-to-live (TTL) value for cached content is smaller than required or no cache expiration rule is created, which causes requests to be frequently redirected to the origin server. In this case, you need to specify a proper TTL value to increase the cache hit ratio and accelerate content retrieval. We recommend that you specify a TTL value based on the following rules: Specify a TTL value of one month or longer for static files that are infrequently updated, such as images and application packages. Specify a TTL value based on your actual workloads for static files that are frequently updated, such as JavaScript and CSS files.	Create a cache rule for resources
   	By default, client requests are redirected to the origin server with the complete URLs retained, including parameters that follow the question mark (?). After you enable the parameter ignoring feature, the parameters that follow the question mark (?) in the request URL are ignored when the client retrieves resources from the origin server. This improves the cache hit ratio and reduces the number of origin requests.	Ignore parameters

   For more information about the causes of low cache hit ratios, see Troubleshoot low cache hit ratios.

2. Bandwidth monitoring and alerts

   To prevent bandwidth spikes caused by attacks, you can configure the monitoring and alerting features to monitor bandwidth values. Alternatively, you can specify a bandwidth cap.

   Scenario	Description	Reference
   Prevent high bandwidth values	You can specify a bandwidth cap. If a bandwidth value during a statistical period exceeds the bandwidth cap, Alibaba Cloud CDN suspends acceleration and resolves the domain name to an invalid address offline.***.com, which cannot be accessed.	Configure bandwidth caps
   	You can configure alert rules in CloudMonitor to monitor bandwidth values. This allows you to detect and manage bandwidth anomalies at the earliest opportunity.	Configure alert rules