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Editor's Notes

• #7: Device has also a «non functional» lifetime «Nonfunctional» means that a device needs to run some tasks to manage its lifetime, not really the core device functions. For example, it needs to be configured because it is probably headless, so we have to configure it remotely after initial configuration and deployment. We need also to query devices to perform some analysis, either on some classification information or its state. And we need to perform some actions on devices because conditions change through their lifetime, so we need to run some tasks
• #14: 2/11/2018 6:58 PM
• #16: IoT Hub can scale to million of devices with IoT Hub. But when you scale, you don't think about resource allocation, CPU or memory. You just think about messages. How many messages and devices you need. That's why with IoT Hub you talk about a "unit," that is the scaling element. Each unit has a different capacity in different tier. Each differs in the number of messages a unit can handle per day. But you have to be careful. During the course, you will often meet the notions of message and size. Well, that size is a variable size that depends on by the functionality, for example, 8Kb or 256Kb) The "unit" message size is different. A "unit" message size is a billable message and is a fixed size 4Kb chunk of data in standard tier, 0.5Kb in the free tier or if the message is about device configuration with twins. For instance, if a device sends 16 kilobytes message, in S1, S2, and S3 tiers, it will be billed as four messages. So when you need to configure service to run or scaling, you have to measure you messaging performances. You need to count your devices, your messages, calculate the average size and estimage the number of billable messages. Then you count the number of units you need, and you can change that number during configuration. Or you can deploy other instances of IoT Hub, which is a good practice regarding scalability but also resilience in case of failure. For this last uses, IoT Hub supports you importing and exporting device registry if you need to backup and restore for recovery.
• #19: Device has also a «non functional» lifetime «Nonfunctional» means that a device needs to run some tasks to manage its lifetime, not really the core device functions. For example, it needs to be configured because it is probably headless, so we have to configure it remotely after initial configuration and deployment. We need also to query devices to perform some analysis, either on some classification information or its state. And we need to perform some actions on devices because conditions change through their lifetime, so we need to run some tasks
• #25: IoTHub contains an identity registry to stores all the information about devices. On this registry, you can perform some operations. Create device identity Update device identity Retrieve device identity Delete device identity List all the stored identities Export all identities to Azure blob storage Import identities from Azure blob storage All the operations are available by a REST API so you can build your device registration tool inside your required device management workflow. You can also use one of the SDKs available for the major programming languages and platforms.
• #28: Tampering is the modification of a device to induce failure or altering its behavior. Information disclosure threats involve the exposure of information to individuals who are not supposed to have access to it—for example, the ability of users to read a file that they were not granted access to, or the ability of an intruder to read data in transit between two computers. Denial of service (DoS) attacks deny service to valid users—for example, by making a Web server temporarily unavailable or unusable. You must protect against certain types of DoS threats simply to improve system availability and reliability. In this type of threat, an unprivileged user gains privileged access and thereby has sufficient access to compromise or destroy the entire system. Elevation of privilege threats include those situations in which an attacker has effectively penetrated all system defenses and become part of the trusted system itself, a dangerous situation indeed. An example of identity spoofing is illegally accessing and then using another user's authentication information, such as username and password Data tampering involves the malicious modification of data. Examples include unauthorized changes made to persistent data, such as that held in a database, and the alteration of data as it flows between two computers over an open network, such as the Internet. Repudiation threats are associated with users who deny performing an action without other parties having any way to prove otherwise—for example, a user performs an illegal operation in a system that lacks the ability to trace the prohibited operations. Nonrepudiation refers to the ability of a system to counter repudiation threats. For example, a user who purchases an item might have to sign for the item upon receipt. The vendor can then use the signed receipt as evidence that the user did receive the package.
• #32: So when you have an identity, you can interact with the device and perform some non functional tasks, for maintenance. There are some operations that you can perform with devices. Device Twin Synchronize the device condition and configuration between cloud and device Queries Dynamic reporting across device twin and jobs to attest device status and health Methods Perform interactive actions on devices Then there are Jobs, but we don’t cover that in this lecture.
• #38: All the device twins are persisted in the registry, in a sort of NoSQL database. All data in the twins can be queried with an SQL-like language to perform any listing or summary query for statistics or deep dive evaluations. It contains extensions for the IoTHub requirements. FROM clause allow selecting documents allowed, at the moment the only allowed keywords are devices or jobs. WHERE clause allows expressing filter predicated on the twin document structure. Root properties are tags, properties.Reported, properties.desired and you can. You can fully write predicates to include or exclude devices for the result of the query. You can also use functions to manipulate data such as math functions, type testing functions, string manipulation functions. SELECT allow to project twin property values or tags, so to represent the correct data set minimizing data or to evaluate some summarizing values with aggregate functions GROUP BY allow aggregating values by some values
• #41: Direct methods represent a request-reply interaction with a device similar to an HTTP call in that they succeed or fail immediately (after a timeout). You use Direct methods for operations that require immediate confirmation A device receives direct methods through a device-specific MQTT topic. In fact, it is only supported MQTT. If you need to use AMQP, you cannot use Direct methods. It’s a two-way data flow. There is a limitation with data exchanged as you can exchange 8Kb in the request and 8Kb in the response. When the device is disconnected, IoTHub cannot reach it. The backend receives a notification when the device is disconnected. You can set the timeout you require to understand that the device is offline, in a range from 30sec to 3600sec.