Configure single-request throttling

Usage notes

• Single-request throttling limits the data transfer rate from a POP to a client, which may degrade the download experience. Use this feature with caution.

• Throttling does not apply to files smaller than the configured rate. For example, a 10 KB file is not affected by a 1 Mbps limit.

• Throttling works best with large files. For example, a 1 Mbps limit is effective for a 500 MB file.

• The minimum rate limit is 100 KB/s.

• Without a rule condition, configure only one throttling rule. If multiple rules exist, only the first one applies.

• With a rule condition, the priority of associated conditions in the rules engine determines the execution order, not the order in which rules are configured.

Procedure

1. Log on to the CDN console.

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

3. On the Domain Names page, find the target domain name and click Manage in the Actions column.

4. In the domain's navigation pane, click Traffic Throttling.

5. On the Traffic Throttling for Individual Requests tab, click Create Rule, and configure the parameters.

   Parameter	Description
   Default Limit	The maximum download speed for a single request. The minimum value is 100 KB/s. Note If you configure only the Default Limit parameter, the limit applies to all requests for the accelerated domain name served by POPs. To set up advanced rules such as time-based throttling, configure the other parameters.
   No Throttling	The amount of data that can be sent before throttling takes effect. Unit: bytes. Default value: 0.
   Name of the Custom Throttling Parameter	When configured, POPs extract this parameter from the request URL and use its value as the speed limit. For example, if you set Name of the Custom Throttling Parameter to rate, select MB as the Unit of the Custom Throttling Parameter, and set Default Limit to 200 KB/s: if a request URL contains the rate parameter, the speed is limited to the parameter value (minimum 100 KB/s); if the URL does not contain the rate parameter, the default 200 KB/s limit applies.
   Unit of the Custom Throttling Parameter	The unit for the custom throttling parameter value.
   Start Time of Throttling	The hour (0–24, in 24-hour format) when throttling starts. This value must be less than the end time. Default value: 0. All Alibaba Cloud CDN POPs use Beijing Time (UTC+8). For example, a start time of 20 means throttling begins at 20:00:00 (UTC+8). To set different start times for different countries, use a rule condition to match the client's geographic location.
   End Time of Throttling	The hour (0–24, in 24-hour format) when throttling ends. This value must be greater than the start time. Default value: 24. All Alibaba Cloud CDN POPs use Beijing Time (UTC+8). For example, an end time of 22 means throttling ends at 22:00:00 (UTC+8). To set different end times for different countries, use a rule condition to match the client's geographic location.
   Rule Condition	A rule condition allows a rule to be applied only when a request meets specific criteria. Important When a feature references rule conditions, the execution order follows the priority of the associated rule conditions, not the order of the feature configurations. Do not use: Disables conditional rules. You can add or edit conditional rules in the Rules engine.

6. Click OK.

Configuration example

The following example shows a throttling configuration for the accelerated domain name example.aliyundoc.com:

The Rate Limit is 200 KB/s, the URL Parameter for Rate Limiting is rate, the Unrestricted Size is not set, the Rate Limit Start Time is 0, the Rate Limit End Time is 24, and the Rule Condition is not used.

• If a client requests https://example.aliyundoc.com/image.jpg, the server responds with the content at a maximum download speed of 200 KB/s.

• If a client requests https://example.aliyundoc.com/image.jpg?rate=100, the server responds with the content at a maximum download speed of 100 MB/s.

FAQ

• Q: My throttling configuration is not working. How can I troubleshoot it? How long does it take for the configuration to take effect?

  A: Throttling configurations typically take effect immediately. If a limit is not being applied, check the following:

  1. Browser cache: The browser may serve a locally cached file instead of sending a new request to CDN. Clear your browser cache or use a different browser to test.

  2. Chunked downloads (Range requests): If the client supports chunked downloads, each chunk is treated as an independent request. The No Throttling threshold resets for each chunk, which may prevent the speed limit from taking effect.

  3. Check response headers: Inspect the request's response headers to confirm that the throttling policy was applied.

• Q: What is the scope of traffic throttling for individual requests? Is the limit calculated independently for each URL?

  A: Single-request throttling limits the speed of each individual request. Requests to different URLs are throttled independently. When the data sent for a request reaches the configured no-throttling size threshold, the CDN POP begins throttling that request.

• Q: When I seek in a video, which triggers a Range request, is the No Throttling threshold reset?

  A: Yes. Seeking to a new position triggers a new Range request with an HTTP 206 status code. CDN treats this as a new request, so the No Throttling threshold resets and data from previous requests does not count toward the new limit.