Download acceleration

Download acceleration is primarily intended for use with downloads of large files of 20 MB or more. For example, it’s used with download delivery for software installation packages, game clients, apps, or videos. The Azure Content Delivery Network caches files to Content Delivery Network edge nodes to relieve bandwidth pressure on source station downloads and improve the download experience for users.

Download acceleration is suitable for use in scenarios such as downloading operating system and firmware upgrades, game clients, mobile app updates, and computer applications.

This article discusses the creation of download acceleration domain names. For more information about how to create Content Delivery Network acceleration nodes, see Use the Azure Content Delivery Network.

Default cache rules for download acceleration

The Content Delivery Network sets default cache rules for download acceleration (see the following). You also can customize cache rules based on your needs. For more information, see the Azure Content Delivery Network portal advanced management help file “Domain Name Management”. If the source station content is changed or updated, but the cache time-to-live (TTL) hasn’t expired, you can manually refresh the cache files and synchronize the updated source station content in real time. For more information, see the Azure Content Delivery Network portal advanced management help file “Cache Refresh.”

The system’s default cache rules for download acceleration

  1. Dynamic files aren’t cached. Dynamic files have extensions like .php, .aspx, .asp, .jsp, and .do.
  2. Files with the following extensions are cached for one month: .7z, .apk, .wdf, .cab, .dhp, .exe, .flv, .gz, .ipa, .iso, .mpk, .mpq, .pbcv, .pxl, .qnp, .r00, .rar, .xy, .xy2, and .zip.

Create domain names for download acceleration

  1. In the Azure portal navigation pane, select “CDN.”
  2. In the function area, select Create New. In the Create New dialog box, select App Services, CDN, and Quick Create.
  3. In the Acceleration Type drop-down list, select Download Acceleration.

    Acceleration type selection

  4. In the Origin Domain Type drop-down list, select cloud service, storage account, web app, or a customized origin domain. Note: “Download Acceleration” does not support the “Media Service” origin domain type.

  5. In the Origin Domain drop-down list, select one option from the list of available cloud services, storage accounts, or web apps for use in creating the Content Delivery Network endpoint.
    Origin domain options

    If the selected origin domain type is Customized Origin Domain, enter your own origin domain address under Origin Domain. You can enter one or multiple origin domain IP addresses. Separate the multiple addresses with semicolons, for example,;

    Customized origin domain selection

  6. In Custom Domain, enter the custom domain name that you want to use, for example, Custom domains support extensive domain name acceleration.

  7. In Origin Host Header, enter the return-to-source access host header accepted by your source station. After you enter the custom domain, the system automatically fills in a default value based on the origin domain type that you selected. To be more specific: If your source station is on Azure, the default value is the corresponding source station address. If your source station isn’t on Azure, the default value is the custom domain that you entered. You also can also modify this based on the actual configuration of your source station.

    If the origin domain type is a storage account, the corresponding return-to-source host header is:

    Storage account

    If the origin domain type is a custom origin domain, the corresponding return to source host header is:

    Custom origin domain

  8. In “ICP Number,” enter the corresponding ICP record number for the custom domain that you entered (for example, Jing ICP Bei XXXXXXXX Hao-X).

    ICP record number

  9. Click Create to create the new endpoint.

After you have created the endpoint, it appears in the list of subscribed endpoints. The list view shows the custom domains that are used to access cached content, as well as the origin domains. The origin domain is the original location of the content that is cached on the CDN. Custom domains are URLs that are used to access Content Delivery Network cache content.

Custom domains and origin domains

Note: Configurations created for endpoints aren’t immediately available. They must be reviewed to check that the ICP custom domain name matches the ICP number. For more information, see the second half of “Step 2: Create a new Content Delivery Network endpoint” in Use the Azure Content Delivery Network.