LPWAN Static Context Header Compression (SCHC) for CoAP
draft-ietf-lpwan-coap-static-context-hc-13

Document Type Active Internet-Draft (lpwan WG)
Last updated 2020-03-25 (latest revision 2020-03-05)
Replaces draft-toutain-lpwan-coap-static-context-hc
Stream IETF
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lpwan Working Group                                          A. Minaburo
Internet-Draft                                                    Acklio
Intended status: Standards Track                              L. Toutain
Expires: September 6, 2020        Institut MINES TELECOM; IMT Atlantique
                                                            R. Andreasen
                                             Universidad de Buenos Aires
                                                          March 05, 2020

        LPWAN Static Context Header Compression (SCHC) for CoAP
               draft-ietf-lpwan-coap-static-context-hc-13

Abstract

   This draft defines the way SCHC (Static Context Header Compression)
   header compression can be applied to the CoAP protocol.  SCHC is a
   header compression mechanism adapted for constrained devices.  SCHC
   uses a static description of the header to reduce the redundancy and
   the size of the information in the header.  While
   [I-D.ietf-lpwan-ipv6-static-context-hc] describes the SCHC
   compression and fragmentation framework, and its application for
   IPv6/UDP headers, this document applies the use of 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 how to apply 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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 6, 2020.

Minaburo, et al.        Expires September 6, 2020               [Page 1]
Internet-Draft           LPWAN CoAP compression               March 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
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Table of Contents

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