# DFU Service Characteristics

The "DFU Service Characteristics and Their Properties" table lists the DFU service characteristics and provides information about them.

Table: DFU Service Characteristics and Their Properties
Characteristic | UUID | Properties | Length | Description | Requirements
Transport | b2152466-d601-11e8-9f8b-f2801f1b9fd1 | Notify, Write without response | variable (max. 512) | Internally used characteristic to transport data with the DFU protocol. | Mandatory for DFU component, prohibited for device application.
Device ID | b2152466-d602-11e8-9f8b-f2801f1b9fd1 | Read | 16 | Device ID as found in the version info of the FOTA stack sub-image. Only FOTA images with the same device ID are compatible, unless this characteristic is all 0s, in which case all FOTA images are compatible. | Mandatory for DFU component, optional for device application.
BootLoader Version | b2152466-d603-11e8-9f8b-f2801f1b9fd1 | Read | 8 (Format struct version) | Version of the installed BootLoader. | Mandatory for DFU component, optional for device application.
FOTA Stack Version | b2152466-d604-11e8-9f8b-f2801f1b9fd1 | Read | 8 (Format struct version) | Version of the installed FOTA stack sub-image (of type struct version). | Mandatory for DFU component, optional for device application
Application Version | b2152466-d605-11e8-9f8b-f2801f1b9fd1 | Read | 8 (Format struct version) | Version of the installed application sub-image. If no valid application sub-image is currently installed, then all 0s is returned. | Mandatory for DFU component, optional for device application.
FOTA Stack Build ID | b2152466-d606-11e8-9f8b-f2801f1b9fd1 | Read | 32 | Build ID as found in the descriptor of the FOTA stack sub-image. If the Build ID of the FOTA image to download is different from the one in this characteristic, then both sub-images must be updated; otherwise, updating only the application sub-image is sufficient. | Mandatory for DFU component, optional for device application
Enter DFU | b2152466-d607-11e8-9f8b-f2801f1b9fd1 | Write | 1 | A write with the value 1 switches from the Application mode to the DFU mode. | Prohibited for DFU component, mandatory for device application.