Observing Resources in CoAP
draft-ietf-core-observe-04

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Document Type Active Internet-Draft (core WG)
Last updated 2011-02-07 (latest revision 2010-10-18)
Replaces draft-hartke-coap-observe
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CoRE Working Group                                             K. Hartke
Internet-Draft                                   Universitaet Bremen TZI
Intended status: Standards Track                       February 14, 2012
Expires: August 17, 2012

                      Observing Resources in CoAP
                       draft-ietf-core-observe-04

Abstract

   CoAP is a RESTful application protocol for constrained nodes and
   networks.  The state of a resource on a CoAP server can change over
   time.  This document specifies a simple protocol extension for CoAP
   that gives clients the ability to observe such changes.

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
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   This Internet-Draft will expire on August 17, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Background . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Protocol Overview  . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Design Philosophy  . . . . . . . . . . . . . . . . . . . .  5
     1.4.  Conformance Requirements . . . . . . . . . . . . . . . . .  6
   2.  The Observe Option . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Client-side Requirements . . . . . . . . . . . . . . . . . . .  7
     3.1.  Request  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Notifications  . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Caching  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.4.  Reordering . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.5.  Cancellation . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  Server-side Requirements . . . . . . . . . . . . . . . . . . . 10
     4.1.  Request  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.2.  Notifications  . . . . . . . . . . . . . . . . . . . . . . 10
     4.3.  Caching  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.4.  Reordering . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.5.  Retransmission . . . . . . . . . . . . . . . . . . . . . . 12
   5.  Intermediaries . . . . . . . . . . . . . . . . . . . . . . . . 13
   6.  Block-wise Transfers . . . . . . . . . . . . . . . . . . . . . 14
   7.  Discovery  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     11.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 17
     A.1.  Proxying . . . . . . . . . . . . . . . . . . . . . . . . . 20
     A.2.  Block-wise Transfer  . . . . . . . . . . . . . . . . . . . 22
   Appendix B.  Modeling Resources to Tailor Notifications  . . . . . 22
   Appendix C.  Changelog . . . . . . . . . . . . . . . . . . . . . . 23
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25

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1.  Introduction

1.1.  Background

   CoAP [I-D.ietf-core-coap] is an Application Protocol for Constrained
   Nodes/Networks.  It is intended to provide RESTful services [REST]
   not unlike HTTP [RFC2616] while reducing the complexity of
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