Range origin fetch enables a CDN point of presence (POP) to include a Range header in origin requests so that the origin server returns only the specified portion of a resource. This improves file delivery efficiency, reduces back-to-origin traffic, lowers the load on your origin server, and speeds up response times.
Background
The HTTP Range header specifies which part of a resource to retrieve. For example, Range: bytes=0-100 requests the first 101 bytes of a file.
After you enable range origin fetch, when a POP receives a request for a resource that is not cached or has expired, the POP fetches only the required segments from the origin server by using Range requests and caches them locally.
How range origin fetch works:
Usage notes
Before you enable range origin fetch:
Make sure your origin server supports Range requests and can respond with
206 Partial Content. If it does not, enabling this feature may cause caching issues or request failures.Range origin fetch is disabled by default.
Multipart Ranges is disabled by default and is not enabled by range origin fetch. To enable it, submit a ticket.
Enabling range origin fetch increases origin fetch QPS, which may trigger rate limiting on your origin server. To avoid this, call the DescribeL2VipsByDomain operation to retrieve the IP addresses of origin-pull POPs and add them to your origin server's IP allowlist.
Use cases for large files
CDN supports progressive streaming for large files such as MP4. The behavior depends on your origin server's Range request support and the origin fetch mode configured in the CDN console:
Scenario 1: Origin server supports Range requests and range origin fetch is enabled
When the client sends a Range request and range origin fetch is enabled, the POP fetches only the requested data range from the origin server and returns it to the client. The POP does not wait for the entire file to download. Progressive streaming is supported.
Scenario 2: Client does not send a Range request
If a client requests a complete file without a Range header, the POP requests the complete file from the origin and streams it to the client. Because the data is forwarded as it is received, the client can start playback immediately (provided that the MP4 moov atom is in the file header), but cannot seek to a position that has not yet been downloaded. In this scenario, the range origin fetch configuration does not affect the client-side transfer behavior.
Scenario 3: Origin server does not support Range requests
If the origin server does not support Range requests and cannot respond with 206, range origin fetch has no effect even if enabled. The POP fetches the complete file instead. Verify that your origin server supports Range requests before enabling this feature.
MP4 and similar formats support streaming, but the underlying HTTP transport must support Range requests. Verify that your origin server supports Range requests and select the appropriate origin fetch mode based on your requirements.
Procedure
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Log on to the CDN console.
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In the left navigation pane, click Domain Names.
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On the Domain Names page, find the target domain name and click Manage in the Actions column.
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In the domain's navigation pane, click Video.
In the Range Origin Fetch section, click Modify.
Based on the following table, select Do Not Enable Range Origin Fetch, Match Client, or Enable Range Origin Fetch (Recommended for Large File Delivery).
If you select Match Client or Enable Range Origin Fetch (Recommended for Large File Delivery), you can set the shard size. The default shard size is 512 KB.
Parameter
Option
Description
Example
Range Origin Fetch
Do Not Enable Range Origin Fetch
By default, Do Not Enable Range Origin Fetch is selected, which means that regardless of whether a client sends a Range request to a CDN POP, the CDN POP requests the entire file during an origin fetch, resulting in low file distribution efficiency for large files.
For example, if a request from a client to a CDN POP contains
Range: bytes=0-100, the CDN POP sends a request to the origin server without the Range parameter. The origin server sends the entire file to the CDN POP. For example, if the file is 10 MB, the origin server sends the 10 MB file to the CDN POP. The CDN POP caches the file that it receives from the origin server and then responds to the client with the content for theRange: bytes=0-100request.Match Client
After you enable Match Client, if a client sends a Range request to a CDN POP, the CDN POP performs an origin fetch by using a Range request. For the first origin fetch request, the CDN POP requests a data block from your origin server. The size of this block is determined by rounding up the range size from the client's request to the nearest integer multiple of the shard size. All subsequent origin fetch requests use the shard size that you specify.
For example, when the shard size is 512 KB, if a client sends a request to a CDN POP that contains
Range:bytes=0-614399(which is 600 KB), and the file is not cached on the CDN POP, the first origin fetch retrieves a 1024 KB shard (600 KB rounded up to 1024 KB). For subsequent requests for other uncached shards of the file, the CDN POP accesses the origin server by using a shard size of 512 KB.Enable Range Origin Fetch (Recommended for Large File Delivery)
After Enable Range Origin Fetch (Recommended for Large File Delivery) is enabled, regardless of whether a client sends a Range request to a CDN POP, CDN POPs always use Range requests for origin fetch. All Range requests sent from CDN POPs to the origin server use the shard size that you specify.
None
Shard Size
512 KB
1 MB
2 MB
4 MB
You can set the shard size if you select Match Client or Enable Range Origin Fetch (Recommended for Large File Delivery). The default size is 512 KB.
1 MB
Rule Condition
A rule condition evaluates request parameters to determine whether a configuration applies.
ImportantWhen a feature uses rule conditions from the rules engine, execution follows rule condition priority, not feature configuration order.
Do not use conditions: Disables conditional rules.
You can add or edit conditional rules in Rules engine.
A rule condition evaluates parameters in a user request to determine whether the configuration applies.
Do not use
Click OK to save the configuration.