Extended Tokens and Stateless Clients in the Constrained Application Protocol (CoAP)
draft-hartke-core-stateless-01

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CoRE Working Group                                             K. Hartke
Internet-Draft                                                  Ericsson
Updates: 7252, 8323 (if approved)                     September 18, 2018
Intended status: Standards Track
Expires: March 22, 2019

                 Extended Tokens and Stateless Clients
             in the Constrained Application Protocol (CoAP)
                     draft-hartke-core-stateless-01

Abstract

   This document provides considerations for alleviating CoAP clients
   and intermediaries of maintaining per-request state.  Additionally,
   it introduces a new, optional CoAP protocol extension for extended
   token lengths.

   This document updates RFCs 7252 and 8323.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on March 22, 2019.

Copyright Notice

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

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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   4
   2.  Extended Tokens . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Extended Token Length (TKL) Field . . . . . . . . . . . .   4
     2.2.  Discovering Support . . . . . . . . . . . . . . . . . . .   4
       2.2.1.  Extended-Token-Lengths Capability Option  . . . . . .   5
       2.2.2.  Trial and Error . . . . . . . . . . . . . . . . . . .   5
     2.3.  Intermediaries  . . . . . . . . . . . . . . . . . . . . .   6
   3.  Stateless Clients . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Intermediaries  . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Extended Tokens . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Message Transmission  . . . . . . . . . . . . . . . . . .   9
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  CoAP Signaling Option Number  . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Updated Message Formats  . . . . . . . . . . . . . .  11
     A.1.  CoAP over UDP . . . . . . . . . . . . . . . . . . . . . .  12
     A.2.  CoAP over TCP . . . . . . . . . . . . . . . . . . . . . .  13
     A.3.  CoAP over WebSockets  . . . . . . . . . . . . . . . . . .  14
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The Constrained Application Protocol (CoAP) [RFC7252] is a RESTful
   application-layer protocol for constrained environments [RFC7228].
   In CoAP, clients (or intermediaries in the client role) make requests
   to servers (or intermediaries in the server role), which serve the
   requests by returning responses.

   While a request is ongoing, a client typically maintains some state
   that it requires for processing the response when it arrives.
   Identification of this state is done by means of a _token_ in CoAP,
   an opaque sequence of bytes chosen by the client and included in the
   CoAP request.  The server returns the token verbatim in any resulting
   CoAP response (Figure 1).

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          +-----------------+     request with     +------------+
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