CoAP Traffic
draft-toutain-lpwan-coap-traffic-00

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Network Working Group                                        A. Minaburo
Internet-Draft                                                    Acklio
Intended status: Informational                                L. Toutain
Expires: July 16, 2017                 Institut Mines Telecom Atlantique
                                                        January 12, 2017

                              CoAP Traffic
                  draft-toutain-lpwan-coap-traffic-00

Abstract

   This document describes different CoAP scenarios for the SCHC
   compression.  It goes from the simplest exchange without
   acknowledgments to a basic study of the CoMI traffic.

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1.  Introduction

   This document describes different CoAP scenarios for the SCHC
   compression.  It goes from the simplest exchange without
   acknowledgments to a basic study of the CoMI traffic.  These
   scenarios currently do not cover cases where encryption is used
   (COSE, OSCOAP,...).

2.  scenario 1 - Unidirectional traffic

2.1.  CoAP POST without Acknowledgement from thing

   The thing sends a CoAP POST/PUT request without acknowledgment using
   CoAP NON message and no response option [RFC7967].  This is a common
   traffic in a LPWAN network to minimize the downlink.

 thing                          LPWAN SCHC                   CoAP Server
|                                |                                |
|                                |   NON POST MID=0x00AB          |
|                                |   Token = 0x11                 |
|                                |   Path = /elm1/elm2            |
|                                |   Content-format = val         |
|                                |   NoResponse = 0|2|8|16        |
|     rule-id value              |   Value                        |
|------------------------------->|                                |
|                                | ------------------------------>|

                        Figure 1: POST with no ACK

   Compression Objectives:

   o  do not send version, type, token length, code because they are
      defined in the rule.

   o  compress Message ID and Token.

   o  do not sent options because they are defined in the rule.

   o  send value

   *** NOTE: The Mid may not be sent, since no acknowledgement is
   expected.  Nevertheless several copies of the same message will not
   be detected by the receiver which will view them as several requests.

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   This can be solved at L2 if the technology sends the frame with
   unique value.

2.2.  Scenario 2 - CoAP POST without Acknowledgement to thing

   Same as Section 2.1 but request comes from network to thing.
   Selected values for Mid, token need to be control to allow a better
   compression rate.  A CoAP proxy is need to normalize these values.

  thing                          LPWAN SCHC                  CoAP Server
  |                                |                                |
  |                                |   NON POST MID=0xCDAB          |
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