CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets
RFC 8323

Document Type RFC - Proposed Standard (February 2018; No errata)
Last updated 2018-11-01
Replaces draft-tschofenig-core-coap-tcp-tls, draft-bormann-core-block-bert, draft-bormann-core-coap-sig, draft-savolainen-core-coap-websockets
Stream IETF
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Reviews
Stream WG state Submitted to IESG for Publication (wg milestone: Oct 2016 - CoAP over TCP, TLS, ... )
Document shepherd Jaime Jimenez
Shepherd write-up Show (last changed 2017-03-21)
IESG IESG state RFC 8323 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Alexey Melnikov
Send notices to "Jaime Jimenez" <jaime.jimenez@ericsson.com>
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
Internet Engineering Task Force (IETF)                        C. Bormann
Request for Comments: 8323                       Universitaet Bremen TZI
Updates: 7641, 7959                                             S. Lemay
Category: Standards Track                             Zebra Technologies
ISSN: 2070-1721                                            H. Tschofenig
                                                                ARM Ltd.
                                                               K. Hartke
                                                 Universitaet Bremen TZI
                                                           B. Silverajan
                                        Tampere University of Technology
                                                          B. Raymor, Ed.
                                                           February 2018

 CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets

Abstract

   The Constrained Application Protocol (CoAP), although inspired by
   HTTP, was designed to use UDP instead of TCP.  The message layer of
   CoAP over UDP includes support for reliable delivery, simple
   congestion control, and flow control.

   Some environments benefit from the availability of CoAP carried over
   reliable transports such as TCP or Transport Layer Security (TLS).
   This document outlines the changes required to use CoAP over TCP,
   TLS, and WebSockets transports.  It also formally updates RFC 7641
   for use with these transports and RFC 7959 to enable the use of
   larger messages over a reliable transport.

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
   https://www.rfc-editor.org/info/rfc8323.

Bormann, et al.              Standards Track                    [Page 1]
RFC 8323         TCP/TLS/WebSockets Transports for CoAP    February 2018

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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 ....................................................3
   2. Conventions and Terminology .....................................6
   3. CoAP over TCP ...................................................7
      3.1. Messaging Model ............................................7
      3.2. Message Format .............................................9
      3.3. Message Transmission ......................................11
      3.4. Connection Health .........................................12
   4. CoAP over WebSockets ...........................................13
      4.1. Opening Handshake .........................................15
      4.2. Message Format ............................................15
      4.3. Message Transmission ......................................16
      4.4. Connection Health .........................................17
   5. Signaling ......................................................17
      5.1. Signaling Codes ...........................................17
      5.2. Signaling Option Numbers ..................................18
      5.3. Capabilities and Settings Messages (CSMs) .................18
      5.4. Ping and Pong Messages ....................................20
      5.5. Release Messages ..........................................21
      5.6. Abort Messages ............................................23
      5.7. Signaling Examples ........................................24
   6. Block-Wise Transfer and Reliable Transports ....................25
      6.1. Example: GET with BERT Blocks .............................27
      6.2. Example: PUT with BERT Blocks .............................27
   7. Observing Resources over Reliable Transports ...................28
      7.1. Notifications and Reordering ..............................28
      7.2. Transmission and Acknowledgments ..........................28
      7.3. Freshness .................................................28
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