IoT Protocols

   1.  Link Layer

·         Link layer protocols define physically- how the data is sent over the physical layer network's or medium (e.g., copper wire, coaxial cable, or a radio wave).

·         this layer is connected with the local network.

·         This layer defines “how the packets are coded and signalled by the hardware device over the medium to which the host is attached (such as a coaxial cable, twisted-pair wire or an optical fibre).

 ·         Ethernet IEEE 802.3 is a collection of wired Ethernet standards for the link layer.

o   For example, following standard used in shared medium in:-

o   IEEE 802.3 (10BASE5 Ethernet):- coaxial cable.

o   IEEE 802.3.i (10BASE-T Ethernet):- copper twisted-pair connections.

o   IEEE 802.3.j (10BASE-F Ethernet):- fibre optic connections.

o   IEEE 802.3ae (10 Gbit/s Ethernet):-  fibre, and so on. 

·         These standards provide data rates from 10 Mb/s to 40 Gb/s and higher.

·         In this network, data sent by one device can be received by all the devices connected to it, depending on its transmission conditions and transceiver capabilities.

·         Other ethernet standards protocols are :-

·         IEEE 802.11 - WiFi : wireless local area network (WLAN) communication (operates in the 2.4/5 GHz band to 60 GHz bands (data rates 1 Mb/s to upto 6.75 Gb/s) )

·         WiMax standards provide data rates from 1.5 Mb/s to 1 Gb/s ((802.16m) provides data rates of 100 Mbit/s for mobile stations and I Gbit/s for fixed stations). 

·         IEEE 802.15.4 - LR-WPAN: (low-rate wireless personal area networks) use for high level communication protocols provide data rates from 40 Kb/s 250 Kb/s such as ZigBee.

·         Provide low-cost and low-speed communication for power constrained devices ( 2G/3G/4G - Mobile Communication): (2G including GSM and CDMA), (3G-including UMTS and CDMA2000) and (4G-including LTE).

·         IoT devices based on these standards can communicate over cellular networks.

2- Network/Internet Layer

·         Responsible for sending of IP datagrams from the source network to the destination network.

·         Performs the host addressing and packet routing across multiple networks.

·         Host identification is by hierarchical IP addressing schemes such as IPv4 or IPv6.

IPv4: (Internet Protocol version 4)

·         This Internet protocol is used to identify the devices on a network by a hierarchical addressing scheme.

·         IPv4 uses a 32-bit address scheme (total of 232 or 4,294,967,296 addresses).

·         It has been succeeded by IPv6.

·         In this protocol IP protocols establish connections on packet networks, without guarantee of packets delivery.

·         Guaranteed delivery and data integrity are handled by the upper layer protocols (such TCP).

 IPv6 : (Internet Protocol version 6)

·         It is the newest version of Internet protocol and successor of IPv4.

·         It is use 128-bit address scheme(total 21 or 3.4% 10 addresses).

6LoWPAN (IPv6 over Low power Wireless Personal Area Networks):-

·         It is IP protocol to the low-power devices ( limited processing capability).

·         Operates in the 2.4 ghz frequency range and provides data transfer rates 250 Kb/s.

·         Defines compression mechanisms for ipv6 datagrams over IEEE 802.15.4-based networks.

3.Transport Layer

·         The transport layer protocols provide end-to-end message transfer capability.

·         In this layer message transfer after the set up on connections as either using handshakes (as in TCP) or without handshake/acknowledgements (as in UDP).

·         This layer provides functions such as error control, segmentation, flow control and congestion control.

TCP: (Transmission Control Protocol)

·         Most widely used transport layer protocol, used by web browsers.

·         It is use HTTPS application layer protocols, email programs (SMTP application layer protocol) and file transfer (FTP).

·         TCP is a connection oriented and stateful protocol, ensures reliable transmission of packets and also, provides error detection capability so that duplicate packets can be discarded and lost packets are retransmitted.

·         The flow control capability ensures that rate at the sender is not too high for the receiver to process.

·         The congestion control capability of TCP helps in avoiding network congestion and congestion collapse which can lead to degradation of network performance.

• UDP (User Datagram Protocol):-

·         UDP is connectionless, transaction oriented and stateless protocol.

·         useful for time-sensitive applications (for very small data units to exchange and do not want the overhead of connection setup).

·         Not provide guaranteed to delivery, ordering of messages and duplicate elimination.

4. Application Layer

·         Application layer protocols define “how the applications interface with the lower layer protocols to send the data over the network”.

·         The application data, typically in files, is encoded by the application layer protocol and encapsulated in the transport layer protocol which provides connection or transaction-oriented communication over the network.

·         Port numbers are used for application addressing (for example port 80 for HTTP. port 22 for SSH. etc.).

·         Application layer protocols enable process-to-process connections using ports.

HTTP: (Hypertext Transfer Protocol)

·         Application layer protocol that forms the foundation of the World Wide Web (WWW).

·         Includes commands such as GET, PUT, POST DELETE, HEAD, TRACE, OPTIONS, etc.

·         It follows a request-response model where a client sends requests to a server using the HTTP commands.

·         It is a stateless protocol and each HTTP request is independent to other requests.

·         An HTTP client can be a browser or an application running on the client (e.g., an application running on an loT device a mobile application.pr other software).

·         HTTP protocol uses Universal Resource Identifiers (URIS) to identify HTTP resources HTTP.

• COAP: (Constrained Application Protocol)

·         It is an application layer protocol for machine-to-machine (M2M) applications.

·         It is a web transfer protocol and uses a request-response model.

·         it runs on top of UDP instead of TCP.

·         It uses a client-server architecture where clients communicate with servers using connectionless datagrams.

·         It is designed to easy interface with HTTP.

·         Like HTTP, COAP supports methods such as GET, PUT, POST, and DELETE.

• WebSocket:

·         WebSocket protocol allows full-duplex communication over a single socket connection for sending messages between client and server.

·         It is based on TCP and allows streams of messages to be sent back and forth between the client and server while keeping the TCP connection open.

·         The client can be a browser a mobile application or an loT device.

• MQTT : (Message Queue Telemetry Transport)

·         It is a light weight messaging protocol based on the publish-subscribe model.

·         It uses a client-server architecture where the client (such as an loT device) connects to the server (also called MQTT Broker) and publishes messages to topics on the server.

·         The broker forwards the messages to the clients subscribed to topics MOTT is well suited for constrained environments where the devices have limited processing and memory resources and the network bandwidth is low.

XMPP : (Extensible Messaging and Presence Protocol )

·         It is a protocol for real-time communication and streaming XML data between network entities in IOT devices.

·         It is use in wide range of applications including messaging, presence, data syndication, gaming, multi-party chat and voice/video calls.

·         It allows sending small chunks" of XML data from one network entity to another in near real-time.

·         It is a decentralized protocol and uses a client-server architecture.

·         It supports both client-to-server and server-to-server communication paths.

Data Distribution Service (DDS):-

·         It is a data-centric middleware standard for device-to-device or machine-to-machine communication.

·         It uses a publish-subscribe model where publishers (e.g. devices that generate data) create topics to which subscribers (e.g.. devices that want to consume data) can subscribe.

·         Publisher is an object responsible for data distribution and the subscriber is responsible for receiving published data.

·         DDS provides quality-of-service (QoS) control and configurable reliability.

Advanced Message Queuing Protocol (AMQP):-

·         It is an open application layer protocol for business messaging.

·         it supports both point-to-point and publisher/subscriber models, routing and queuing.

·         It’s brokers receive messages from publishers (e.g.. devices or applications that generate data) and route them over connections to consumers (applications that process data).

·         Publishers publish the messages to exchanges which then distribute message copies to queues.

·         Messages are either delivered by the broker to the consumers which have subscribed to the queues or the consumers can pull the messages from the queues.

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