Additional Topics > Medical Imaging in IDL > Using IDL DICOM Network Services > Default Application Entities

## Default Application Entities

The DICOM Network Services utility defines four default Application Entities:

- IDL_AE_QUERY_SCU — uses the Query SCU service, which lets you ask a device (a file source) about DICOM files contained in its database. This service works in conjunction with the Query SCP service, which allows you retrieve DICOM files from the remote node. On the file source device (the server in this instance), the Query SCP service listens for and responds to queries. It also listens for requests and sends the specified DICOM files.
- IDL_AE_STOR_SCP — uses the Storage SCP service, which listens at the defined TCP/IP port for incoming DICOM files and writes them to a local disk directory.
- IDL_AE_STOR_SCU — uses the Storage SCU service, which lets you send local DICOM files to a remote node.
- IDL_AE_ECHO_SCU — uses the Echo SCU service, which lets you determine if a remote SCP node is accessible.

The network characteristics of the default entities can be modified, but they cannot be deleted. You can also define new AEs. See the following section for details:

- Defining a New Application Entity
- Modifying an Application Entity
- Deleting an Application Entity

### Replacing a Default Entity

You can use the default IDL_AE_ECHO_SCU, IDL_AE_QUERY_SCU, and IDL_AE_STOR_SCU Application Entities for echo, query and send operations without making any modifications. If you decide to define new entities to replace these, you will need to select the entity in the Configuration tab.

After defining a new entity as described in Defining a New Application Entity in the following section, complete the following steps:

1. Open the DICOM Network Services utility by entering:

   DICOMEX_NET

2. In the upper right quadrant of the Configuration tab, select the name of the new Application Entity in the Application Entity Name droplist to indicate the entity to be associated with the Echo SCU, Query Retrieve SCU or Storage SCU services.
3. Click Save to record the changes.