Azure IoT Hub Overview

Azure IoT Hub

• A cloud-hosted solution back end (Platform-as-a-service, PaaS) to connect Securely and Reliably to any device in field. Provides Per-device authentication, Device Management, Scaled Provisioning.
• Available as an on-premises solution using Azure Stack Hub.

IoT Hub Variations

• Two tiers/packages of IoT Hub:
  • Basic Tier
    • provides a subset of features and is intended for solutions that only need uni-directional communication from devices to the cloud.
  • Standard Tier
    • To develop full-featured and bi-directional communication capabilities
    • device-to-cloud telemetry
    • Per-device identity
    • Message routing
    • message enrichments
    • Event Grid integration
    • support for HTTP, AMQP, and MQTT protocol
    • Device Provisioning Service
    • Monitoring and diagnostics
    • Cloud-to-device messaging
    • Device twins
    • Module twins
    • Device management
    • Device streams
    • Azure IoT Edge
    • IoT Plug and Play Preview
• Both tiers offer same kind of security and authentication.
• IoT Hub is available in 3 sizes, to choose from depending upon the Data Throughput you are considering. Each unit of a level 1 IoT hub can handle 400 thousand messages a day, while a level 3 unit can handle 300 million.

Protocol support

• IoT Hub supports following protocols for device connection:
  • MQTT
  • MQTT over WebSocket
  • HTTPS 1.1
  • AMQP
  • AMQP over WebSocket

Device Identity Registry:

• Stores information about the devices and modules permitted to connect to the IoT Hub.
• Devices needs to authenticate with the credentials stored in the registry.

Authentication:

• Grants access to endpoints by verifying a token against the shared access policies and identity registry security credentials.
• Supported certificates:
  • An existing X.509 certificate
  • CA-signed X.509 certificate
  • A self-generated and self-signed X-509 certificate

Device Twin:

• JSON documents that store device state information, including metadata, configurations, and conditions.
• Maintains a device twin for each device that you connect to IoT Hub.

IoT Hub Endpoints:

• Send device-to-cloud messages
• Receive cloud-to-device messages
• Initiate file uploads
• Retrieve and update device twin properties
• Receive direct method requests
• Additional (custom) endpoints for Azure services:
  • Azure Storage containers
  • Event Hubs
  • Service Bus Queues
  • Service Bus Topics

Device Provisioning Service:

• Enables zero-touch, just-in-time provisioning to the right IoT Hub (~regional) without requiring human intervention, allowing the customers to provision millions of devices in a secure and scalable manner.

Telemetry Function:

• The telemetry function involves recording and transmitting values received by an IoT device.

Direct Method invocation from IoT Hub:

• Represent a request-reply interaction with a device.
• This approach is useful for scenarios where the course of immediate action is different depending on whether the device was able to respond.
• Each device method targets a single device.
  • Schedule jobs on multiple devices shows how to provide a way to invoke direct methods on multiple devices, and schedule method invocation for disconnected devices.
• May have zero or more inputs/parameters in the method payload. (max. payload size = 128KB)
• Invoked through a service-facing URI: {iot hub}/twins/{device id}/methods/.
• Device receives direct methods through a device-specific MQTT topic: $iothub/methods/POST/{method name}/ or through AMQP links.
• Direct methods are synchronous and either succeed or fail after the timeout period (default: 30 seconds, settable between 5 and 300 seconds)
• There is no guarantee on ordering or any concurrency semantics on method calls.
• further details

Schedule Jobs on IoT devices

• Jobs execute device twin updates and direct methods against a set of devices at a scheduled time.
• Consider using jobs when you need to schedule and track progress any of the following activities on a set of devices:
  • Update desired properties
  • Update tags
  • Invoke direct methods
• Job Properties
  • jobId
  • startTime, endTime
  • type:
    • scheduleUpdateTwin: A job used to update a set of desired properties or tags.,
    • scheduleDeviceMethod: A job used to invoke a device method on a set of device twins.
  • status:
    • pending, scheduled, running, cancelled, failed, completed
  • deviceJobStatistics:
    • deviceCount
    • failedCount
    • succeededCount
    • runningCount
    • pendingCount

Cloud-to-device communication ways

• Direct methods
  • Used for communications that require immediate confirmation of the result.
  • Direct methods are often used for interactive control of devices such as turning on a fan.
• Twin’s desired properties
  • Used for long-running commands intended to put the device into a certain desired state.
  • For example, set the telemetry send interval to 30 minutes.
• Cloud-to-device messages
  • Used for one-way notifications to the device app.
• Further detailed comparison of the various cloud-to-device communication options

Azure IoT Hub on Premise:

• Running your Azure IoT Hub based solution on-premises!
• Bring your whole IoT Solution on premises

Lambda/Serverless Architecture few points to note:

• The Lambda architecture of Azure IoT enables multiple paths for data storage and processing.
• Possible issues with Lambda architecture:
  • Duplication of data and code.
  • Greater chance of an unwanted divergence between the duplicate copies.
  • There may be code duplication in the analysis apps, if there are separate apps for the hot and cold paths.
  • Costs:
    • Fast services tend to be the more expensive, slower services cheaper.
    • There’s usually a compromise to be made.

References

• Azure IoT Samples