- Constrained Application Protocol
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Constrained Application Protocol (CoAP), is a RESTful protocol for use with constrained networks and nodes. CoAP easily translates to HTTP for integration with the web while meeting specialized requirements such as multicast support, very low overhead and simplicity for constrained environments.[1][2] The Internet Engineering Task Force (IETF) Constrained RESTful environments (CoRE) Working Group has done the major standardization work for this protocol. In order to make the protocol suitable to Internet of Things(IoT) and M2M applications, various new functionalities have been added.
This protocol is still under development.
Features
The CoRE group has proposed the following features for CoAP:
- RESTful protocol design minimizing the complexity of mapping with HTTP.
- Low header overhead and parsing complexity.
- URI and content-type support.
- Support for the discovery of resources provided by known CoAP services.
- Simple subscription for a resource, and resulting push notifications.
- Simple caching based on max-age.
The mapping of CoAP with HTTP is also defined, allowing proxies to be built providing access to CoAP resources via HTTP in a uniform way.
Message Formats
CoAP makes use of two message types, requests and responses, using a simple binary base header format. The base header may be followed by options in ICMP-style Type-Length-Value format. CoAP is by default bound to UDP and optionally to TCP as described in Section 4.
Any bytes after the headers in the packet are considered the message body if any. The length of the message body is implied by the datagram length. When bound to UDP the entire message MUST fit within in a single datagram. When used with 6LoWPAN [RFC4944], messages SHOULD fit into a single 802.15.4 frame to minimize fragmentation.
References
- ^ Constrained Application Protocol (CoAP) draft-shelby-core-coap-07 https://datatracker.ietf.org/doc/draft-ietf-core-coap/
- ^ "Integrating Wireless Sensor Networks with the Web" , Walter, Colitti 2011
Categories:- Network protocols
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