LPWAN Static Context Header Compression (SCHC) for CoAP
draft-ietf-lpwan-coap-static-context-hc-16

Document Type Active Internet-Draft (lpwan WG)
Authors Ana Minaburo  , Laurent Toutain  , Ricardo Andreasen 
Last updated 2020-10-20
Replaces draft-toutain-lpwan-coap-static-context-hc
Stream IETF
Intended RFC status Proposed Standard
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Document shepherd Pascal Thubert
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lpwan Working Group                                          A. Minaburo
Internet-Draft                                                    Acklio
Intended status: Standards Track                              L. Toutain
Expires: April 23, 2021           Institut MINES TELECOM; IMT Atlantique
                                                            R. Andreasen
                                             Universidad de Buenos Aires
                                                        October 20, 2020

        LPWAN Static Context Header Compression (SCHC) for CoAP
               draft-ietf-lpwan-coap-static-context-hc-16

Abstract

   This draft defines how Static Context Header Compression (SCHC) can
   be applied to the Constrained Application Protocol (CoAP).  SCHC is a
   header compression mechanism adapted for constrained devices.  SCHC
   uses a static description of the header to reduce the redundancy and
   size of the header's information.  While RFC 8724 describes the SCHC
   compression and fragmentation framework, and its application for
   IPv6/UDP headers, this document applies SCHC for CoAP headers.  The
   CoAP header structure differs from IPv6 and UDP since CoAP uses a
   flexible header with a variable number of options, themselves of
   variable length.  The CoAP protocol messages format is asymmetric:
   the request messages have a header format different from the one in
   the response messages.  This specification gives guidance on applying
   SCHC to flexible headers and how to leverage the asymmetry for more
   efficient compression Rules.

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
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 23, 2021.

Minaburo, et al.         Expires April 23, 2021                 [Page 1]
Internet-Draft           LPWAN CoAP compression             October 2020

Copyright Notice

   Copyright (c) 2020 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  SCHC Applicability to CoAP  . . . . . . . . . . . . . . . . .   4
   3.  CoAP Headers compressed with SCHC . . . . . . . . . . . . . .   7
     3.1.  Differences between CoAP and UDP/IP Compression . . . . .   8
   4.  Compression of CoAP header fields . . . . . . . . . . . . . .   9
     4.1.  CoAP version field  . . . . . . . . . . . . . . . . . . .   9
     4.2.  CoAP type field . . . . . . . . . . . . . . . . . . . . .   9
     4.3.  CoAP code field . . . . . . . . . . . . . . . . . . . . .   9
     4.4.  CoAP Message ID field . . . . . . . . . . . . . . . . . .  10
     4.5.  CoAP Token fields . . . . . . . . . . . . . . . . . . . .  10
   5.  CoAP options  . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  CoAP Content and Accept options.  . . . . . . . . . . . .  11
     5.2.  CoAP option Max-Age, Uri-Host, and Uri-Port fields  . . .  11
     5.3.  CoAP option Uri-Path and Uri-Query fields . . . . . . . .  11
       5.3.1.  Variable-length Uri-Path and Uri-Query  . . . . . . .  12
       5.3.2.  Variable number of Path or Query elements . . . . . .  12
     5.4.  CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme
           fields  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     5.5.  CoAP option ETag, If-Match, If-None-Match, Location-Path,
           and Location-Query fields . . . . . . . . . . . . . . . .  13
   6.  SCHC compression of CoAP extension RFCs . . . . . . . . . . .  13
     6.1.  Block . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.2.  Observe . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.3.  No-Response . . . . . . . . . . . . . . . . . . . . . . .  13
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