Constrained Application Protocol (CoAP)

Document Type Replaced Internet-Draft (individual)
Last updated 2010-08-24 (latest revision 2010-05-10)
Replaces draft-shelby-6lowapp-coap
Replaced by draft-ietf-core-coap
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Intended RFC status (None)
Expired & archived
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IESG IESG state Replaced by draft-ietf-core-coap
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document specifies the Constrained Application Protocol (CoAP), a specialized transfer protocol for use with constrained networks and nodes for machine-to-machine applications such as smart energy and building automation. These constrained nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while networks such as 6LoWPAN often have high packet error rates and typical throughput of 10s of kbps. CoAP provides request/reply and subscribe/notify interaction models between appliciation end-points, supports built-in resource discovery, and includes key web concepts such as URIs and RESTful methods. 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.


Zach Shelby (
Brian Frank (
Don Sturek (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)