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Constrained Application Protocol (CoAP) is a software protocol intended to be used in very simple electronics devices that allows them to communicate interactively over the Internet. It is particularly targeted for small low power sensors, switches, valves and similar components that need to be controlled or supervised remotely, through standard Internet networks. CoAP is an application layer protocol that is intended for use in resource-constrained internet devices, such as WSN nodes. CoAP is designed to easily translate to HTTP for simplified integration with the web, while also meeting specialized requirements such as multicast support, very low overhead, and simplicity.〔(RFC describing Constrained Application Protocol (CoAP) )〕〔"(Integrating Wireless Sensor Networks with the Web )" , Walter, Colitti 2011〕 Multicast, low overhead, and simplicity are extremely important for Internet of Things (IoT) and Machine-to-Machine (M2M) devices, which tend to be deeply embedded and have much less memory and power supply than traditional internet devices have. Therefore, efficiency is very important. CoAP can run on most devices that support UDP or a UDP analogue. 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 IoT and M2M applications, various new functionalities have been added.〔(The CORE WG's IETF Area )〕 The core of the protocol is specified in RFC 7252, important extensions are in various stages of the standardization process. == Features == The CoRE group has designed CoAP with the following features in mind: * 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.〔(Best practices for HTTP-CoAP mapping implementation )〕 With the introduction of CoAP, a complete networking stack of open standard protocols that are suitable for constrained devices and environments, becomes available.〔(IETF Standardization in the Field of the Internet of Things (IoT): A Survey )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Constrained Application Protocol」の詳細全文を読む スポンサード リンク
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