# MediaTailor CDN integration and parameter routing
<a name="manifest-query-parameters-cdn-integration"></a>

AWS Elemental MediaTailor manifest query parameters enable sophisticated CDN integration scenarios. You can use them for dynamic routing, authorization, and load balancing.

**CDN routing use cases**  
Common CDN integration scenarios that benefit from manifest query parameters include the following:
+ **Geographic routing:** Route requests to region-specific MediaTailor endpoints based on viewer location
+ **Token-based authorization:** Pass authorization tokens through the CDN to MediaTailor for secure content access
+ **Load balancing:** Distribute traffic across multiple MediaTailor endpoints using CDN routing logic
+ **A/B testing:** Route different user segments to different MediaTailor configurations for testing
+ **Device-specific optimization:** Route requests based on device type or capabilities

**Parameter preservation across CDN layers**  
MediaTailor ensures that manifest query parameters are preserved across multiple CDN layers and request types:

1. **Initial request:** Parameters are extracted from the session initialization request

1. **Manifest generation:** Parameters are applied to all relevant URLs in the manifest

1. **Segment requests:** Parameters are included in all segment URLs for consistent CDN behavior

1. **Ad insertion:** Parameters are preserved during ad insertion and segment replacement

**Example CDN authorization flow**  
The following example demonstrates a complete CDN authorization flow using manifest query parameters:  

1. Client requests manifest with authorization token:

   ```
   GET https://cdn.example.com/mediatailor/v1/master/123456789/originId/index.m3u8?manifest.auth_token=jwt_token_here&manifest.user_id=12345
   ```

1. CDN forwards request to MediaTailor with parameters:

   ```
   GET https://mediatailor.amazonaws.com/v1/master/123456789/originId/index.m3u8?manifest.auth_token=jwt_token_here&manifest.user_id=12345
   ```

1. MediaTailor generates manifest with parameters applied to all URLs:

   ```
   #EXTM3U
   #EXT-X-STREAM-INF:BANDWIDTH=2665212
   ../../../manifest/123456789/originId/session/0.m3u8?auth_token=jwt_token_here&user_id=12345
   ```

1. Subsequent segment requests include parameters for CDN authorization:

   ```
   GET https://cdn.example.com/mediatailor/segment/123456789/originId/session/0/1?auth_token=jwt_token_here&user_id=12345
   ```