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

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Last updated 2019-03-11
Replaces draft-hartke-core-stateless
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CoRE Working Group                                             K. Hartke
Internet-Draft                                                  Ericsson
Updates: 7252, 8323 (if approved)                         March 11, 2019
Intended status: Standards Track
Expires: September 12, 2019

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

Abstract

   This document provides considerations for alleviating CoAP clients
   and intermediaries of keeping per-request state.  To facilitate this,
   this document additionally introduces a new, optional CoAP protocol
   extension for extended token lengths.

   This document updates RFCs 7252 and 8323.

Status of This Memo

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   This Internet-Draft will expire on September 12, 2019.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Hartke                 Expires September 12, 2019               [Page 1]
Internet-DraftExtended Tokens and Stateless Clients in CoAP   March 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Extended Tokens . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Extended Token Length (TKL) Field . . . . . . . . . . . .   4
     2.2.  Discovering Support . . . . . . . . . . . . . . . . . . .   5
       2.2.1.  Extended-Token-Lengths Capability Option  . . . . . .   5
       2.2.2.  Trial and Error . . . . . . . . . . . . . . . . . . .   5
     2.3.  Intermediaries  . . . . . . . . . . . . . . . . . . . . .   6
   3.  Stateless Clients . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Intermediaries  . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Extended Tokens . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Message Transmission  . . . . . . . . . . . . . . . . . .   9
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     4.1.  Extended Tokens . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  Stateless Clients . . . . . . . . . . . . . . . . . . . .  10
       4.2.1.  Recommended Algorithms  . . . . . . . . . . . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  CoAP Signaling Option Number  . . . . . . . . . . . . . .  11
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Updated Message Formats  . . . . . . . . . . . . . .  12
     A.1.  CoAP over UDP . . . . . . . . . . . . . . . . . . . . . .  13
     A.2.  CoAP over TCP . . . . . . . . . . . . . . . . . . . . . .  14
     A.3.  CoAP over WebSockets  . . . . . . . . . . . . . . . . . .  15
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

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 needs to keep 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
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