Merge pull request #250537 from PatAltimore/patricka-layered-blob-storage

Clarify blob storage module requirement

Author: JamesJBarnett

articles/iot-edge/how-to-configure-api-proxy-module.md

@@ -1,5 +1,6 @@
 ---
-title: Configure API proxy module for Azure IoT Edge
+title: Configure API proxy module
+titlesuffix: Azure IoT Edge
 description: Learn how to customize the API proxy module for IoT Edge gateway hierarchies.
 author: PatAltimore
 
@@ -48,8 +49,8 @@ Currently, the default environment variables include:
 
 | Environment variable | Description |
 | -------------------- | ----------- |
-| `PROXY_CONFIG_ENV_VAR_LIST` | List all the variables that you intend to update in a comma-separated list. This step prevents accidentally modifying the wrong configuration settings.
-| `NGINX_DEFAULT_TLS` | Specifies the list of TLS protocol(s) to be enabled. See NGINX's [ssl_protocols](https://nginx.org/docs/http/ngx_http_ssl_module.html#ssl_protocols).<br><br>Default is 'TLSv1.2'. |
+| `PROXY_CONFIG_ENV_VAR_LIST` | List all the variables that you intend to update in a comma-separated list. This step prevents accidentally modifying the wrong configuration settings. |
+| `NGINX_DEFAULT_TLS` | Specifies the list of TLS protocols to be enabled. See NGINX's [ssl_protocols](https://nginx.org/docs/http/ngx_http_ssl_module.html#ssl_protocols).<br><br>Default is 'TLSv1.2'. |
 | `NGINX_DEFAULT_PORT` | Changes the port that the nginx proxy listens to. If you update this environment variable, you must expose the port in the module dockerfile and declare the port binding in the deployment manifest. For more information, see [Expose proxy port](#expose-proxy-port).<br><br>Default is 443.<br><br>When deployed from the Azure Marketplace, the default port is updated to 8000, to prevent conflicts with the edgeHub module. For more information, see [Minimize open ports](#minimize-open-ports). |
 | `DOCKER_REQUEST_ROUTE_ADDRESS` | Address to route docker requests. Modify this variable on the top layer device to point to the registry module.<br><br>Default is the parent hostname. |
 | `BLOB_UPLOAD_ROUTE_ADDRESS` | Address to route blob registry requests. Modify this variable on the top layer device to point to the blob storage module.<br><br>Default is the parent hostname. |
@@ -141,7 +142,7 @@ Configure the following modules at the **top layer**:
 
 Configure the following module on any **lower layer** for this scenario:
 
-* An API proxy module
+* API proxy module. The API proxy module is required on all lower layer devices except the bottom layer device.
   * Configure the following environment variables:
 
     | Name | Value |
@@ -168,7 +169,7 @@ Configure the following module on any **lower layer** for this scenario:
 
 Port 8000 is exposed by default from the docker image. If a different nginx proxy port is used, add the **ExposedPorts** section declaring the port in the deployment manifest. For example, if you change the nginx proxy port to 8001, add the following to the deployment manifest:
 
-```
+```json
 {
    "ExposedPorts": {
       "8001/tcp": {}
@@ -189,9 +190,7 @@ Port 8000 is exposed by default from the docker image. If a different nginx prox
 
 Another use case for the API proxy module is to enable IoT Edge devices in lower layers to upload blobs. This use case enables troubleshooting functionality on lower layer devices like uploading module logs or uploading the support bundle.
 
-This scenario uses the [Azure Blob Storage on IoT Edge](https://azuremarketplace.microsoft.com/marketplace/apps/azure-blob-storage.edge-azure-blob-storage) module at the top layer to handle blob creation and upload.
-
-In a nested scenario, up to five layers are supported. Each upstream IoT Edge device in the nested hierarchy requires the *Azure Blob Storage on IoT Edge* module. For a sample multi-layer deployment, see the [Azure IoT Edge for Industrial IoT](https://github.com/Azure-Samples/iot-edge-for-iiot) sample.
+This scenario uses the [Azure Blob Storage on IoT Edge](https://azuremarketplace.microsoft.com/marketplace/apps/azure-blob-storage.edge-azure-blob-storage) module at the top layer to handle blob creation and upload. In a nested scenario, up to five layers are supported. The *Azure Blob Storage on IoT Edge* module is required on the top layer device and optional for lower layer devices. For a sample multi-layer deployment, see the [Azure IoT Edge for Industrial IoT](https://github.com/Azure-Samples/iot-edge-for-iiot) sample.
 
 Configure the following modules at the **top layer**: