"Pending" Responses for the Constrained Application Protocol (CoAP)
draft-hartke-core-pending-02

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CoRE Working Group                                       P. van der Stok
Internet-Draft                                                consultant
Intended status: Informational                                 K. Hartke
Expires: August 30, 2018                         Universitaet Bremen TZI
                                                       February 26, 2018

  "Pending" Responses for the Constrained Application Protocol (CoAP)
                      draft-hartke-core-pending-02

Abstract

   This document proposes a new type of response for the Constrained
   Application Protocol (CoAP) called a "Pending" response.  A CoAP
   server can use a Pending response to indicate that it has accepted a
   request but has not yet started processing it or that processing the
   request will take longer than a client is typically willing to wait
   for a response.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on August 30, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Pending Responses . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Observing Resources . . . . . . . . . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Constrained Application Protocol (CoAP) [RFC7252] is a request/
   response protocol not unlike HTTP.  CoAP defines no upper bound for
   the time between a request and the resulting response.  For example,
   a CoAP-over-UDP server is expected to return an empty Acknowledgement
   to the client if it cannot provide a response right away, but there
   is no limit on the time when the server should return the Separate
   Response.

   In particular in the case of requests with long processing times, a
   CoAP client faces the problem that it cannot easily determine how
   long it should wait for the response and whether the CoAP server is
   actually still processing the request.  Long processing times occur,
   for example, when requests need manual intervention to authorize
   their processing, or when they perform a long sequence of remote
   actions.  An example for this is the "possibly long" authorization
   request specified in EST-coaps [I-D.vanderstok-ace-coap-est].

   This document proposes a new kind of response in CoAP, called a
   "Pending" response.  The semantics of this response are modelled
   after the HTTP 202 (Accepted) status code [RFC7231]:

      The 202 (Accepted) status code indicates that the request has been
      accepted for processing, but the processing has not been
      completed.  The request might or might not eventually be acted
      upon, as it might be disallowed when processing actually takes
      place. [...] The representation sent with this response ought to
      describe the request's current status and point to (or embed) a
      status monitor that can provide the user with an estimate of when
      the request will be fulfilled.

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