What is Azure IoT Hub Device Provisioning Service?

The IoT Hub Device Provisioning Service (DPS) is a helper service for IoT Hub that enables zero-touch, just-in-time provisioning to the right IoT hub without requiring human intervention. DPS enables the provisioning of millions of devices in a secure and scalable manner. Many of the manual steps traditionally involved in provisioning are automated with DPS to reduce the time to deploy IoT devices and lower the risk of manual error.

How Device Provisioning Service works

The following diagram describes what goes on behind the scenes to provision a device with DPS.

Before the device provisioning flow begins, there are two manual steps to prepare:

• On the device side, the device manufacturer prepares the device for provisioning by preconfiguring it with its authentication credentials and assigned Device Provisioning Service ID and endpoint.
• On the cloud side, you or the device manufacturer prepares the Device Provisioning Service instance with individual enrollments and enrollment groups that identify valid devices and define how they should be provisioned.

Once the device and cloud are set up for provisioning, the following steps kick off automatically as soon as the device powers on for the first time:

1. The device powers on for the first time, then connects to the DPS endpoint and presents it authentication credentials.
2. The DPS instance checks the identity of the device against its enrollment list. Once the device identity is verified, DPS assigns the device to an IoT hub and registers it in the hub.
3. The DPS instance receives the device ID and registration information from the assigned hub and passes that information back to the device.
4. The device uses its registration information to connect directly to its assigned IoT hub and authenticate.
5. The device and IoT hub begin communicating directly. The DPS instance has no further role as an intermediary unless the device needs to reprovision.

When to use Device Provisioning Service

There are many provisioning scenarios in which DPS is an excellent choice for getting devices connected and configured to IoT Hub, such as:

• Zero-touch provisioning to a single IoT solution without hardcoding IoT Hub connection information at the factory (initial setup)
• Load-balancing devices across multiple hubs
• Connecting devices to their owner's IoT solution based on sales transaction data (multitenancy)
• Connecting devices to a particular IoT solution depending on use-case (solution isolation)
• Connecting a device to the IoT hub with the lowest latency (geo-sharding)
• Reprovisioning based on a change in the device
• Rolling the keys used by the device to connect to IoT Hub (when not using X.509 certificates to connect)

Provisioning of nested IoT Edge devices (parent/child hierarchies) isn't currently supported by DPS.

Provisioning process

There are two steps that take place ahead of a device provisioning with DPS:

• The manufacturing step in which the device is created and prepared at the factory, and
• The cloud setup step in which the Device Provisioning Service is configured for automated provisioning.

Both of these steps can be incorporated into existing manufacturing and deployment processes. DPS even simplifies some deployment processes that involve manual work to get connection information onto the device.

Manufacturing step

This step is all about what happens on the manufacturing line. The roles involved in this step include silicon designer, silicon manufacturer, integrator and/or the end manufacturer of the device. This step is concerned with creating the hardware itself.

Also in this step, the manufacturer supplies the device deployer/operator with identifying key information. Supplying that information could be as simple as confirming that all devices have an X.509 certificate generated from a signing certificate provided by the device deployer/operator, or as complicated as extracting the public portion of a TPM endorsement key from each TPM device. Many silicon manufacturers offer these services.

Cloud setup step

This step is about configuring the cloud for proper automatic provisioning. Generally there are two types of users involved in the cloud setup step: someone who knows how devices need to be initially set up (a device operator), and someone else who knows how devices are to be split among the IoT hubs (a solution operator).

There's a one-time initial setup of the provisioning service, which the solution operator usually handles. Once the provisioning service is configured, it doesn't have to be modified unless the use case changes.

After the service is configured for automatic provisioning, it must be prepared to enroll devices. This step is done by the device operator, who knows the desired configuration of the devices and makes sure that the provisioning service can properly attest to a device's identity. The device operator takes the identifying key information from the manufacturer and adds it to the enrollment list. There can be subsequent updates to the enrollment list as new entries are added or existing entries are updated with the latest information about the devices.

Registration and provisioning

Provisioning means various things depending on the industry in which the term is used. In the context of provisioning IoT devices to their cloud solution, provisioning is a two part process:

• The first part is establishing the initial connection between the device and the IoT solution by registering the device.
• The second part is applying the proper configuration to the device based on the specific requirements of the solution it was registered to.

Once both of those two steps have been completed, we can say that the device has been fully provisioned. Some cloud services only provide the first step of the provisioning process, registering devices to the IoT solution endpoint, but don't provide the initial configuration. DPS automates both steps to provide a seamless provisioning experience for the device.

Features of the Device Provisioning Service

DPS has many features, making it ideal for provisioning devices.

• Secure attestation support for both X.509 and TPM-based identities.
• Enrollment list containing the complete record of devices/groups of devices that may at some point register. The enrollment list contains information about the desired configuration of the device once it registers, and it can be updated at any time.
• Multiple allocation policies to control how DPS assigns devices to IoT hubs in support of your scenarios: Lowest latency, evenly weighted distribution (default), and static configuration. Latency is determined using the same method as Traffic Manager. Custom allocation, which lets you implement your own allocation policies via webhooks hosted in Azure Functions is also supported.
• Monitoring and diagnostics logging to make sure everything is working properly.
• Multi-hub support allows DPS to assign devices to more than one IoT hub. DPS can talk to hubs across multiple Azure subscriptions.
• Cross-region support allows DPS to assign devices to IoT hubs in other regions.
• Encryption for data at rest allows data in DPS to be encrypted and decrypted transparently using 256-bit AES encryption, one of the strongest block ciphers available, and is FIPS 140-2 compliant.

You can learn more about the concepts and features involved in device provisioning by reviewing the DPS terminology article along with the other conceptual articles in the same section.

Cross-platform support

Just like all Azure IoT services, DPS works cross-platform with various operating systems. Azure offers open-source SDKs in various languages to facilitate connecting devices and managing the service. DPS supports the following protocols for connecting devices:

• HTTPS
• AMQP
• AMQP over web sockets
• MQTT
• MQTT over web sockets

DPS only supports HTTPS connections for service operations.

Regions

DPS is available in many regions. The list of supported regions for all services is available at Azure Regions. You can check availability of the Device Provisioning Service on the Azure Status page.

For resiliency and reliability, we recommend deploying to one of the regions that support Availability Zones.

Data residency consideration

Device Provisioning Service stores customer data. By default, customer data is replicated to a secondary region to support disaster recovery scenarios. For deployments in China East and China North, customers can choose to keep their data only within that region by disabling disaster recovery. For more information, see Cross-region replication in Azure.

DPS uses the same device provisioning endpoint for all provisioning service instances, and performs traffic load balancing to the nearest available service endpoint. As a result, authentication secrets may be temporarily transferred outside of the region where the DPS instance was initially created. However, once the device is connected, the device data flows directly to the original region of the DPS instance. To ensure that your data doesn't leave the original or secondary region, use a private endpoint. To learn how to set up private endpoints, see DPS support for virtual networks.

Quotas and Limits

Each Azure subscription has default quota limits in place that could impact the scope of your IoT solution. The current limit is 10 Device Provisioning Service instances per subscription.

For more information about quota limits, see Azure Subscription Service Limits.

The following table lists the limits that apply to Azure IoT Hub Device Provisioning Service resources.

Resource	Limit	Adjustable?
Maximum device provisioning services per Azure subscription	10	No
Maximum number of registrations	1,000,000	No
Maximum number of individual enrollments	1,000,000	No
Maximum number of enrollment groups (X.509 certificate)	100	No
Maximum number of enrollment groups (symmetric key)	100	No
Maximum number of CAs	25	No
Maximum number of linked IoT hubs	50	No
Maximum size of message	96 KB	No

The Device Provisioning Service has the following rate limits.

Rate	Per-unit value	Adjustable?
Operations	1,000/min/service	No
Device registrations	1,000/min/service	No
Device polling operation	5/10 sec/device	No

Related Azure components

DPS automates device provisioning with Azure IoT Hub. Learn more about IoT Hub.

Next steps

You now have an overview of provisioning IoT devices in Azure. The next step is to try out an end-to-end IoT scenario.

Set up IoT Hub Device Provisioning Service with the Azure portal

Create and provision a simulated device