InternetOFThings_network_communicqtionCoAP_.pptx
- 1. CoAP
- 2. U & P U Patel Department of Computer Engineering What Is CoAP Protocol? • CoAP is an IoT protocol. CoAP stands for Constrained Application Protocol, and it is defined in RFC 7252. • CoAP is a simple protocol with low overhead specifically designed for constrained devices (such as microcontrollers) and constrained networks. • Web transfer protocol for use with constrained nodes and networks. • Designed for Machine to Machine (M2M) applications such as smart energy and building automation. • Based on Request‐Response model between end‐points • Client‐Server interaction is asynchronous over a datagram oriented transport protocol such as UDP
- 3. U & P U Patel Department of Computer Engineering Features of CoAP protocols • The main features of CoAP protocols are: • Web protocol used in M2M with constrained requirements • Asynchronous message exchange • Low overhead and very simple to parse • URI and content-type support • Proxy and caching capabilities
- 4. U & P U Patel Department of Computer Engineering Protocol Layers • There are two different layers that make CoAp protocol: Messages and Request/Response. • The Messages layer deals with UDP and with asynchronous messages. • The Request/Response layer manages request/response interaction based on request/response messages. • CoAP supports four different message types: • Confirmable • Non-confirmable • Acknowledgment • Reset
- 5. U & P U Patel Department of Computer Engineering CoAP terminology • Endpoint: An entity that participates in the CoAP protocol. Usually, an Endpoint is identified with a host • Sender: The entity that sends a message • Recipient: The destination of a message • Client: The entity that sends a request and the destination of the response • Server: The entity that receives a request from a client and sends back a response to the client
- 6. U & P U Patel Department of Computer Engineering CoAP Messages Model • This is the lowest layer of CoAP. • This layer deals exchawith UDP nging messages between endpoints. • Each CoAP message has a unique ID; this is useful to detect message duplicates. • A CoAP message is built by these parts: • A binary header • A compact options • Payload
- 7. U & P U Patel Department of Computer Engineering Confirmable message Confirmable message • A confirmable message is a reliable message. • When exchanging messages between two endpoints, these messages can be reliable. • In CoAP, a reliable message is obtained using a Confirmable message (CON). • Using this kind of message, the client can be sure that the message will arrive at the server. • A Confirmable message is sent again and again until the other party sends an acknowledge message (ACK). • The ACK message contains the same ID of the confirmable message (CON).
- 8. U & P U Patel Department of Computer Engineering Rest message • If the server has troubles managing the incoming request, it can send back a Rest message (RST) instead of the Acknowledge message (ACK)
- 9. U & P U Patel Department of Computer Engineering Non-confirmable messages • The other message category is the Non-confirmable (NON) messages. • These are messages that don’t require an Acknowledge by the server. • They are unreliable messages or in other words messages that do not contain critical information that must be delivered to the server. • To this category belongs messages that contain values read from sensors. • Even if these messages are unreliable, they have a unique ID.
- 10. U & P U Patel Department of Computer Engineering CoAp Request/Response Model • The CoAP Request/Response is the second layer in the CoAP abstraction layer. • The request is sent using a Confirmable (CON) or Non- Confirmable (NON) message. • There are several scenarios depending on if the server can answer immediately to the client request or the answer if not available. • If the server can answer immediately to the client request, then if the request is carried using a Confirmable message (CON), the server sends back to the client an Acknowledge message containing the response or the error code • In the CoAP message, there is a Token. The Token is different from the Message-ID and it is used to match the request and the response.
- 11. U & P U Patel Department of Computer Engineering CoAp Request/Response Model • If the server can’t answer to the request coming from the client immediately, then it sends an Acknowledge message with an empty response. • As soon as the response is available, then the server sends a new Confirmable message to the client containing the response. • At this point, the client sends back an Acknowledge message: • If the request coming from the client is carried using a NON-confirmable message, then the server answer using a NON-confirmable message.
- 12. U & P U Patel Department of Computer Engineering CoAp Message Format Where: • Ver: It is a 2 bit unsigned integer indicating the version • T: it is a 2 length • Code: It is the code bit unsigned integer indicating the message type: 0 confirmable, 1 non- confirmable • TKL: Token Length is the token 4 bit response (8 bit length) • Message ID: It is the message ID expressed with 16 bit
- 13. U & P U Patel Department of Computer Engineering References https://dzone.com/articles/coap-protocol-step-by-step-guide https://coap.technology/impls.html