Merge pull request #233954 from kgremban/apr10-bug60128

Bug -- Clarify device state interval behavior

Author: prmerger-automator[bot]

articles/iot-central/core/howto-manage-devices-individually.md

@@ -82,7 +82,7 @@ Watch the following video to learn more about how to monitor device connection s
 
 > [!VIDEO https://www.youtube.com/embed/EUZH_6Ihtto]
 
-You can include connection and disconnection events in  [Export IoT data to cloud destinations using Blob Storage](howto-export-to-blob-storage.md). To learn more, see [React to IoT Hub events > Limitations for device connected and device disconnected events](../../iot-hub/iot-hub-event-grid.md#limitations-for-device-connected-and-device-disconnected-events).
+You can include connection and disconnection events in  [Export IoT data to cloud destinations using Blob Storage](howto-export-to-blob-storage.md). To learn more, see [React to IoT Hub events > Limitations for device connected and device disconnected events](../../iot-hub/iot-hub-event-grid.md#limitations-for-device-connection-state-events).
 
 ## Add a device
 

articles/iot-hub/iot-hub-event-grid.md

@@ -1,6 +1,7 @@
 ---
-title: Azure IoT Hub and Event Grid | Microsoft Docs
-description: Use Azure Event Grid to trigger processes based on actions that happen in IoT Hub.  
+title: Azure IoT Hub and Event Grid
+titleSuffix: Azure IoT Hub
+description: Use Azure Event Grid to send notifications and trigger processes based on actions that happen in IoT Hub.  
 author: kgremban
 
 ms.service: iot-hub
@@ -17,9 +18,9 @@ Azure IoT Hub integrates with Azure Event Grid so that you can send event notifi
 
 [Azure Event Grid](../event-grid/overview.md) is a fully managed event routing service that uses a publish-subscribe model. Event Grid has built-in support for Azure services like [Azure Functions](../azure-functions/functions-overview.md) and [Azure Logic Apps](../logic-apps/logic-apps-overview.md), and can deliver event alerts to non-Azure services using webhooks. For a complete list of the event handlers that Event Grid supports, see [An introduction to Azure Event Grid](../event-grid/overview.md).
 
-To watch a video discussing this integration, see [Azure IoT Hub integration with Azure Event Grid](/shows/internet-of-things-show/iot-devices-and-event-grid). 
+To watch a video discussing this integration, see [Azure IoT Hub integration with Azure Event Grid](/shows/internet-of-things-show/iot-devices-and-event-grid).
 
-![Azure Event Grid architecture](./media/iot-hub-event-grid/event-grid-functional-model.png)
+![Diagram that shows Azure Event Grid architecture.](./media/iot-hub-event-grid/event-grid-functional-model.png)
 
 ## Regional availability
 
@@ -70,9 +71,9 @@ The following example shows the schema of a device connected event:
 
 ### Device telemetry schema
 
-Device telemetry messages must be in a valid JSON format with the contentType set to **application/json** and contentEncoding set to **UTF-8** in the message [system properties](iot-hub-devguide-routing-query-syntax.md#system-properties). Both of these properties are case insensitive. If the content encoding is not set, then IoT Hub will write the messages in base 64 encoded format.
+Device telemetry messages must be in a valid JSON format with the contentType set to **application/json** and contentEncoding set to **UTF-8** in the message [system properties](iot-hub-devguide-routing-query-syntax.md#system-properties). Both of these properties are case insensitive. If the content encoding is not set, then IoT Hub writes the messages in base 64 encoded format.
 
-You can enrich device telemetry events before they are published to Event Grid by selecting the endpoint as Event Grid. For more information, see [message enrichments](iot-hub-message-enrichments-overview.md).
+You can enrich device telemetry events before they're published to Event Grid by selecting the endpoint as Event Grid. For more information, see [message enrichments](iot-hub-message-enrichments-overview.md).
 
 The following example shows the schema of a device telemetry event:
 
@@ -165,27 +166,28 @@ For a detailed description of each property, see [Azure Event Grid event schema
 
 ## Filter events
 
-Event Grid enables [filtering](../event-grid/event-filtering.md) on event types, subjects, and data content. While creating the Event Grid subscription, you can choose to subscribe to selected IoT events. 
+Event Grid enables [filtering](../event-grid/event-filtering.md) on event types, subjects, and data content. While creating the Event Grid subscription, you can choose to subscribe to selected IoT events.
 
-- Event type: For the list of IoT Hub event types, see [event types](#event-types).
-- Subject: For IoT Hub events, the subject is the device name. The subject takes the format `devices/{deviceId}`. You can filter subjects based on **Begins With** (prefix) and **Ends With** (suffix) matches. The filter uses an `AND` operator, so events with a subject that match both the prefix and suffix are delivered to the subscriber.
-- Data content: The data content is populated by IoT Hub using the message format. You can choose what events are delivered based on the contents of the telemetry message. For examples, see [advanced filtering](../event-grid/event-filtering.md#advanced-filtering). For filtering on the telemetry message body, you must set the contentType to **application/json** and contentEncoding to **UTF-8** in the message [system properties](./iot-hub-devguide-routing-query-syntax.md#system-properties). Both of these properties are case insensitive.
+* Event type: For the list of IoT Hub event types, see [event types](#event-types).
+* Subject: For IoT Hub events, the subject is the device name. The subject takes the format `devices/{deviceId}`. You can filter subjects based on **Begins With** (prefix) and **Ends With** (suffix) matches. The filter uses an `AND` operator, so events with a subject that match both the prefix and suffix are delivered to the subscriber.
+* Data content: The data content is populated by IoT Hub using the message format. You can choose what events are delivered based on the contents of the telemetry message. For examples, see [advanced filtering](../event-grid/event-filtering.md#advanced-filtering). For filtering on the telemetry message body, you must set the contentType to **application/json** and contentEncoding to **UTF-8** in the message [system properties](./iot-hub-devguide-routing-query-syntax.md#system-properties). Both of these properties are case insensitive.
 
-## Limitations for device connected and device disconnected events
+## Limitations for device connection state events
 
-### Device state events
-
-Device connection state events are available for devices connecting using either the MQTT or AMQP protocol, or using either of these protocols over WebSockets. Requests made only with HTTPS won't trigger device connection state notifications.
+Device connected and device disconnected events are available for devices connecting using either the MQTT or AMQP protocol, or using either of these protocols over WebSockets. Requests made only with HTTPS won't trigger device connection state notifications.
 
 * For devices connecting using Java, Node, or Python [Azure IoT SDKs](iot-hub-devguide-sdks.md) with the [MQTT protocol](../iot/iot-mqtt-connect-to-iot-hub.md) will have connection states sent automatically. 
 * For devices connecting using the Java, Node, or Python [Azure IoT SDKs](iot-hub-devguide-sdks.md) with the [AMQP protocol](iot-hub-amqp-support.md), a cloud-to-device link should be created to reduce any delay in accurate connection states. 
 * For devices connecting using the .NET [Azure IoT SDK](iot-hub-devguide-sdks.md) with the [MQTT](../iot/iot-mqtt-connect-to-iot-hub.md) or [AMQP](iot-hub-amqp-support.md) protocol won’t send a device connected event until an initial device-to-cloud or cloud-to-device message is sent/received.
 * Outside of the Azure IoT SDKs, in MQTT these operations equate to SUBSCRIBE or PUBLISH operations on the appropriate messaging [topics](../iot/iot-mqtt-connect-to-iot-hub.md). Over AMQP these equate to attaching or transferring a message on the [appropriate link paths](iot-hub-amqp-support.md).
 
-### Device state interval
+### Device connection state interval
+
+IoT Hub attempts to report each device connection state change event, but some may be missed. At minimum, IoT Hub reports connection state change events that occur 60 seconds apart from each other. This behavior may lead to outcomes such as multiple device connect events reported with no device disconnect events between them.
 
-IoT Hub does not report each individual device connect and disconnect action, but rather publishes the current connection state taken at a periodic 60 second snapshot. Receiving either the same connection state event with different sequence numbers or different connection state events both mean that there was a change in the device connection state during the 60 second window.
-![image](https://user-images.githubusercontent.com/94493443/178398214-7423f7ca-8dfe-4202-8e9a-46cc70974b5e.png)
+<!--
+![Diagram that shows state change events on a device, and how those events are reported by IoT Hub.](https://user-images.githubusercontent.com/94493443/178398214-7423f7ca-8dfe-4202-8e9a-46cc70974b5e.png)
+-->
 
 ## Tips for consuming events
 
@@ -197,9 +199,6 @@ Applications that handle IoT Hub events should follow these suggested practices:
 
 ## Next steps
 
-* [Try the IoT Hub events tutorial](../event-grid/publish-iot-hub-events-to-logic-apps.md)
 * [Learn how to order device connected and disconnected events](iot-hub-how-to-order-connection-state-events.md)
-* [Learn more about Event Grid](../event-grid/overview.md)
 * [Compare the differences between routing IoT Hub events and messages](iot-hub-event-grid-routing-comparison.md)
-* [Learn how to use IoT telemetry events to implement IoT spatial analytics using Azure Maps](../azure-maps/tutorial-iot-hub-maps.md)
 * [Learn more about how to use Event Grid and Azure Monitor to monitor, diagnose, and troubleshoot device connectivity to IoT Hub](iot-hub-troubleshoot-connectivity.md)

articles/iot-hub/iot-hub-troubleshoot-connectivity.md

@@ -48,7 +48,7 @@ When you use Event Grid to monitor or trigger alerts on device disconnects, make
 
 Explore the following topics to learn more about monitoring device connection events with Event Grid:
 
-* For an overview of using Event Grid with IoT Hub, see [React to IoT Hub events with Event Grid](iot-hub-event-grid.md). Pay particular attention to the [Limitations for device connected and device disconnected events](iot-hub-event-grid.md#limitations-for-device-connected-and-device-disconnected-events) section.
+* For an overview of using Event Grid with IoT Hub, see [React to IoT Hub events with Event Grid](iot-hub-event-grid.md). Pay particular attention to the [Limitations for device connection state events](iot-hub-event-grid.md#limitations-for-device-connection-state-events) section.
 
 * For a tutorial about ordering device connection events, see [Order device connection events from Azure IoT Hub using Azure Cosmos DB](iot-hub-how-to-order-connection-state-events.md).