IIoT/IoT Networking Protocols

The typical network, that is encountered, consists of a source, a data source or multiple data sources consisting of sensors, typically sensors, RFIDs, which collect data and interact with the physical environment, and then the data is sent elsewhere for further processing. We need systems, protocols, solutions, algorithms, which will consume extremely low energy. IoT devices are energy constraints; they are small in size and have the very limited processing power. So, network protocols that are designed for use in IoT should be designed accordingly keeping these constraints in mind.

Challenges in designing IIoT / IoT networks are as follows:

• Heterogeneous Access
• Heterogeneous Devices
• Heterogeneous Traffic
• Constrained Devices

Internet Connectivity for IIoT / IoT based devices

• Proprietary Non-IP based solutions - In terms of interoperability there are vendor-specific sensors; vendor-specific gateways.

1. Vendor-Specific Gateways
2. Vendor-Specific APIs

• Internet Engineering Task Force (IETF) IP based solutions

1. IPv6 over Low Power Wireless Personal Area Network (6LoWPAN)
2. Routing Over Low power and Lossy networks (ROLL) - It is a new kind of routing protocol that can be used for IoT-based applications.
3. Constrained RESTful Environments (CoRE) - It extends the integration of IoT devices from networks to the service level. And this is very essential, it is an important thing, service level; typically about the networks, collecting data from these networks in the context of IoT. It provides a platform for applications meant for constrained IoT devices and useful for IoT environments. This framework views sensors and actuator resources and web resources. The framework is limited to applications, which monitor basic sensors and supervise the actuators. CoAP includes a mechanism for service discovery and this service discovery makes it very interesting.

CoRE Services - CoRE devices are mini web servers that register their resources to the resource directory and registration interface.

• Resource Directory (RD) is a logical network node that stores the information about a specific set of IoT devices.
• In any logical IoT node storing the information about a set of IoT devices.
• The Registration Interface, on the other hand, supports the REST-based protocol.
• The full form of REST architecture is REpresentational State Transfer architecture which supports protocols such as HTTP for the existing internet.
• For IoT, the equivalent of REST is the CoAP.
• IoT client uses the lookup interface for the discovery of IoT devices.
• Now everything is the fine network has been built, but then whether the network is able to offer the quality of service guarantees or at least some acceptable levels of quality of service.

IIoT / IoT Network Quality of Services (QoS) - It talks about offering different surfaces to the IoT applications through controlling the heterogeneous traffic generated by IoT devices. QoS policies for IoT networks includes the following attributes:

• Resource Utilization - It talks about the concept of control on the storage and bandwidth for data reception and transmission. Resources in the context of networks mean different things such as storage, bandwidth, etc. The control over these resources such as storage and bandwidth for reception and transmission is something that has to be considered as a QoS criterion. QoS policies for resource utilization includes the following

1. Resource Limit Policy - Controls the amount of message buffering and useful for memory constraint IoT devices.
2. Time Filter Policy - Controls the data sampling rate and talks about the inter-arrival time to avoid buffer overflow.

• Data Timeliness - It is the measurement of the freshness of particular information; when it is received at the receiver end. It is very much helpful in Healthcare, Industrial, and Military actions, where timely data arrival is critical for taking decisions. It includes the following:

1. Deadline Policy - The maximum interarrival time of data; how much is the maximum inter-arrival time?
2. Latency Budget - The maximum time difference between the data transmission and reception from source end to the receiver end.

• Data Availability - It is a measurement of the amount of valid data, provided by the sender or the producer to the receiver. It includes

1. Durability Policy - It is the control of the degree of data persistence transmitted by the sender. It is ensuring the availability of the data to the receiver even after the sender is unavailable.
2. Life Span Policy - It talks about the control over the duration for which the transmitted data will be valid. How much the data that has been sensed and is being circulated through the network? How much time data is going to survive? How much time data is going to live?
3. History Policy - It is about controlling the number of previous data instances available to the data. In the history of the data, how many such instances are available to the receiver.

• Data Delivery - It measures the successful reception of reliable data, from the sender to the receiver. It includes the following:

1. Reliability Policy - Control of the reliability level associated with the data distribution
2. Transport Priority - Allows transmission of data according to its priority level

Requirements of IoT Network - IIoT / IoT devices will have different components such as the radio interface, the processor, the sensor, and few other components. These IoT devices will collect data, which will be sent through the gateway, maybe a proxy server, or through the internet. The cloud will do storage, processing, etc. and at the cloud, there could be different types of analytics; that could be executed. Based on the analytics, there could be some actuation. So, the network for this needs to follow below criteria's:

• Coverage
• High Throughput
• Low Latency
• Ultra-Reliability
• High Power Efficiency

IIoT / IoT Network Protocols -

• Message Queue Telemetry Transport (MQTT) - It was introduced by IBM and standardized by OASIS in 2013. MQTT is based on the concept of Publish/Subscribe. The advantages of MQTT is that a Publish/Subscribe framework has been proposed, which is very suitable for IoT, because IoT devices typically would be publishing data, sensing data, publishing the data. And, with the help of the subscribers and the clients, who will try to pull the data out of the published, data that is buffered somewhere in some agent. So, this kind of architecture is suitable for IoT and it has the advantage of being reliable, lightweight, and cost-effective. Quality of service (QoS) is very important. So, for QoS of MQTT protocol, there are different transactions that will have to be taken into consideration. The first transaction is basically between the publishing client and the MQTT server. The second transaction is between the MQTT server and the subscribing client. MQTT QoS levels are as follows:

1. QoS 0 - Also known as "at most once" delivery. Best effort & unacknowledged data service. Publisher transmits the message one time to the server and the server transmits it one time to the subscriber. No scope for retry
2. QoS 1 - Also known as "at least once" delivery. Retry is performed until the acknowledgment of the message is received.
3. QoS 2 - Also known as "exactly once" delivery. Ensuring that the retry is performed until the message is delivered exactly once

• Constrained Application Protocol (CoAP) - It is a kind of application layered protocol. It is a kind of session protocol. It is a protocol, which helps ensure running different APIs, different applications in IoT. CoAP defines four types of messages:

1. Conformable message - The recipient must exactly explicitly either acknowledge or reject the message.
2. Non-conformable message - The recipient sends the reset message if it cannot process the message.
3. RST: Reset -
4. Acknowledgment

• Extensible Messaging and Presence Protocol (XMPP) - It is again based on publishing, subscribe, a model that we talked about in the context of MQTT. The communication protocol, XMPP is based on XML, and it uses DTLS secure transport layer at the bottom in the transport layer for transport layer security. This model is decentralized; that means, there is no requirement for having a centralized server. And, it has manifold advantages such as it supports interoperability between heterogeneous networks, heterogeneous devices, and heterogeneous agents. It supports extensibility; that means, supporting privacy lists, multi-user chat, publish/subscribe chat, status notifications, etc.
• Advanced Message Queuing Protocol (AMQP) - This is also based on the publish/subscribe models like MQTT and XMPP. And, it supports two types of the framework: one is the point to point communication and the other one is multi-point communication and is typically used for application such as financial applications, and digital finance. It uses a token-based mechanism for flow control, which ensures that there is no buffer overflow at the receiving end. So, flow control is all about the use of a token-based mechanism.
• IEEE 1888 - This one is an energy-efficient network control protocol, which defines a generalized data exchange protocol between the network components over IPv4 or IPv6. It talks about the use of resource universal resource identifiers and supports different applications for environmental monitoring, energy-saving, central management systems, and so on.
• DDS RTPS - The full form of this thing is Distributed Data Service Real-Time Publish and Subscribe. It is very much attractive for use in IoT networks, this support Publish/Subscribe framework on top of the UDP transport layer protocol. So, it is a data-centric binary protocol and this data in this context are termed as “topics”. There are topics that mean like there are users, which subscribe to a particular topic of interest and the listeners listen to these. There is a single topic that may have multiple speakers of different priorities and this supports enlisted QoS for data distribution in terms of data persistence, maintaining, ensuring, delivery deadline, reliability, the freshness of data, and in a different protocol. The application such as military, industrial, and healthcare monitoring are the ones that find this particular protocol to be of use.

References:

1. Google
2. Industrial Internet of Things Tutorials