Added a new document on prxy support.

Author: Pooja Adhikari

articles/healthcare-apis/dicom/dicom-proxy-url-support.md

@@ -0,0 +1,63 @@
+---
+title: Support for url manipulation for the DICOM service in Azure Health Data Services
+description: Learn how to customize or manipulate the url of the image location that is in response object.
+author: varunbms
+ms.service: azure-health-data-services
+ms.subservice: fhir
+ms.topic: overview
+ms.date: 03/26/2024
+ms.author: buchvarun
+---
+
+# What is URL manipulation
+URl manipulation allows customizing the url of the image location that is in response object.
+
+The Dicom service returns the fully qualified url of the imae location in the response object in the dicom tag (UR)  for following operations:
+1. Retrieve Instance 
+2. Retrieve WorkItems
+3. Retrieve OperationStatus
+4. Resolve QueryTag
+5. Resolve QueryTagError
+
+An example of a standard response for a stow operatoin is as below:
+![alt text](image.png)
+
+Here, the url in the response contains a dicom tag "UR" with the value represents the location of the image.
+
+`https://localhost:63838/v2/partitions/foo/studies/1.2.826.0.1.3680043.8.498.13230779778012324449356534479549187420/series/1.2.826.0.1.3680043.8.498.77033797676425927098669402985243398207/instances/1.2.826.0.1.3680043.8.498.13273713909719068980354078852867170114`
+
+ The hostname of this Url represents the dicom service that is being used. 
+
+ To breakdown the structure of the above urlm it consists of
+ 1. hostname -> https://localhost:63838
+ 2. path -> v2/partitions/foo
+ 3. Dicom web standard path -> studies/1.2.826.0.1.3680043.8.498.13230779778012324449356534479549187420/series/1.2.826.0.1.3680043.8.498.77033797676425927098669402985243398207/instances/1.2.826.0.1.3680043.8.498.13273713909719068980354078852867170114
+
+ The feature allows to manipuate the hostname and the path of the response object if needed.
+
+ # How it works
+ This feature will allow modify the path of response url if directed by client based on the request headers they provided.
+The modified header will be based on following two headers:
+1. x-Forwarded-Host
+2. x-Forwarded-Prefix
+
+These headers are a part of [.net core standard forwarded headers](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/proxy-load-balancer?view=aspnetcore-8.0#forwarded-headers). 
+
+If x-forwarded-host header is present in the request object, it would replace the host name with the value provided.
+
+if x-forwarded-prefix header is present in the request object, it would replace the path with the value provided.
+
+## Example:
+### Response of stow operation of dicom service when the above headers are not provided:
+`https://localhost:63838/v2/partitions/foo/studies/1.2.826.0.1.3680043.8.498.13230779778012324449356534479549187420/series/1.2.826.0.1.3680043.8.498.77033797676425927098669402985243398207/instances/1.2.826.0.1.3680043.8.498.13273713909719068980354078852867170114`
+
+### Response of stow operation of dicom service when the above headers are provided:
+
+![alt text](image-1.png)
+
+ `https://api.powershare.com/newbasePath/studies/1.2.826.0.1.3680043.8.498.13230779778012324449356534479549187420/series/1.2.826.0.1.3680043.8.498.45787841905473114233124723359129632652/instances/1.2.826.0.1.3680043.8.498.12714725698140337137334606354172323212`
+
+ # Things to remember
+ 1. Forwarded headers donot have to be used together. If there is a need to just replace hostname and not path, only forwarded host header can be used. Similarly, if there is a need to just replace path, only forwared prefix header can be used.
+
+ 2. These headers follow the standard .netcore structure.