Constrained Application Protocol (CoAP)
draft-ietf-core-coap-12
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2012-10-01
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draft-shelby-core-coap
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Proposed Standard
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Barry Leiba
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core-chairs@tools.ietf.org, draft-ietf-core-coap@tools.ietf.org
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CoRE Working Group Z. Shelby
Internet-Draft Sensinode
Intended status: Standards Track K. Hartke
Expires: April 4, 2013 C. Bormann
Universitaet Bremen TZI
B. Frank
SkyFoundry
October 1, 2012
Constrained Application Protocol (CoAP)
draft-ietf-core-coap-12
Abstract
The Constrained Application Protocol (CoAP) is a specialized web
transfer protocol for use with constrained nodes and constrained
(e.g., low-power, lossy) networks. The nodes often have 8-bit
microcontrollers with small amounts of ROM and RAM, while constrained
networks such as 6LoWPAN often have high packet error rates and a
typical throughput of 10s of kbit/s. The protocol is designed for
machine-to-machine (M2M) applications such as smart energy and
building automation.
CoAP provides a request/response interaction model between
application endpoints, supports built-in discovery of services and
resources, and includes key concepts of the Web such as URIs and
Internet media types. CoAP easily interfaces with HTTP for
integration with the Web while meeting specialized requirements such
as multicast support, very low overhead and simplicity for
constrained environments.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 4, 2013.
Shelby, et al. Expires April 4, 2013 [Page 1]
Internet-Draft Constrained Application Protocol (CoAP) October 2012
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Features . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2. Constrained Application Protocol . . . . . . . . . . . . . . 10
2.1. Messaging Model . . . . . . . . . . . . . . . . . . . . . 11
2.2. Request/Response Model . . . . . . . . . . . . . . . . . 12
2.3. Intermediaries and Caching . . . . . . . . . . . . . . . 15
2.4. Resource Discovery . . . . . . . . . . . . . . . . . . . 15
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . 15
3.1. Header Format . . . . . . . . . . . . . . . . . . . . . . 16
3.2. Option Format . . . . . . . . . . . . . . . . . . . . . . 17
3.3. Option Jump . . . . . . . . . . . . . . . . . . . . . . . 19
3.4. Option Value Formats . . . . . . . . . . . . . . . . . . 20
3.4.1. uint . . . . . . . . . . . . . . . . . . . . . . . . 21
3.4.2. string . . . . . . . . . . . . . . . . . . . . . . . 21
3.4.3. opaque . . . . . . . . . . . . . . . . . . . . . . . 21
3.4.4. empty . . . . . . . . . . . . . . . . . . . . . . . 22
4. Message Transmission . . . . . . . . . . . . . . . . . . . . 22
4.1. Messages and Endpoints . . . . . . . . . . . . . . . . . 22
4.2. Messages Transmitted Reliably . . . . . . . . . . . . . . 23
4.3. Messages Transmitted Without Reliability . . . . . . . . 24
4.4. Message Correlation . . . . . . . . . . . . . . . . . . . 24
4.5. Message Deduplication . . . . . . . . . . . . . . . . . . 25
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