PATCH and FETCH Methods for the Constrained Application Protocol (CoAP)
RFC 8132
Internet Engineering Task Force (IETF) P. van der Stok
Request for Comments: 8132 Consultant
Category: Standards Track C. Bormann
ISSN: 2070-1721 Universitaet Bremen TZI
A. Sehgal
NAVOMI, Inc.
April 2017
PATCH and FETCH Methods for the Constrained Application Protocol (CoAP)
Abstract
The methods defined in RFC 7252 for the Constrained Application
Protocol (CoAP) only allow access to a complete resource, not to
parts of a resource. In case of resources with larger or complex
data, or in situations where resource continuity is required,
replacing or requesting the whole resource is undesirable. Several
applications using CoAP need to access parts of the resources.
This specification defines the new CoAP methods, FETCH, PATCH, and
iPATCH, which are used to access and update parts of a resource.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8132.
van der Stok, et al. Standards Track [Page 1]
RFC 8132 CoAP FETCH PATCH April 2017
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. FETCH . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. PATCH and iPATCH . . . . . . . . . . . . . . . . . . . . 4
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.4. Terminology and Acronyms . . . . . . . . . . . . . . . . 5
2. FETCH Method . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Response Codes . . . . . . . . . . . . . . . . . . . . . 6
2.2. Error Handling . . . . . . . . . . . . . . . . . . . . . 6
2.3. Option Numbers . . . . . . . . . . . . . . . . . . . . . 7
2.3.1. The Content-Format Option . . . . . . . . . . . . . . 7
2.3.2. The ETag Option . . . . . . . . . . . . . . . . . . . 8
2.4. Working with Observe . . . . . . . . . . . . . . . . . . 8
2.5. Working with Block . . . . . . . . . . . . . . . . . . . 8
2.6. Building FETCH Requests . . . . . . . . . . . . . . . . . 8
2.7. A Simple Example for FETCH . . . . . . . . . . . . . . . 8
3. PATCH and iPATCH Methods . . . . . . . . . . . . . . . . . . 9
3.1. Simple Examples for PATCH and iPATCH . . . . . . . . . . 12
3.2. Response Codes . . . . . . . . . . . . . . . . . . . . . 14
3.3. Option Numbers . . . . . . . . . . . . . . . . . . . . . 14
3.4. Error Handling . . . . . . . . . . . . . . . . . . . . . 15
4. The New Set of CoAP Methods . . . . . . . . . . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1. Normative References . . . . . . . . . . . . . . . . . . 19
7.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
van der Stok, et al. Standards Track [Page 2]
RFC 8132 CoAP FETCH PATCH April 2017
1. Introduction
Similar to HTTP, the GET method defined in [RFC7252] for the
Constrained Application Protocol (CoAP) only allows the specification
of a URI and request parameters in CoAP options, not the transfer of
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