Observe Notifications as CoAP Multicast Responses
draft-tiloca-core-observe-multicast-notifications-03

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CoRE Working Group                                             M. Tiloca
Internet-Draft                                               R. Hoeglund
Updates: 7252, 7641 (if approved)                                RISE AB
Intended status: Standards Track                              C. Amsuess
Expires: January 14, 2021
                                                            F. Palombini
                                                             Ericsson AB
                                                           July 13, 2020

           Observe Notifications as CoAP Multicast Responses
          draft-tiloca-core-observe-multicast-notifications-03

Abstract

   The Constrained Application Protocol (CoAP) allows clients to
   "observe" resources at a server, and receive notifications as unicast
   responses upon changes of the resource state.  In some use cases,
   such as based on publish-subscribe, it would be convenient for the
   server to send a single notification to all the clients observing a
   same target resource.  This document defines how a CoAP server sends
   observe notifications as response messages over multicast, by
   synchronizing all the observers of a same resource on a same shared
   Token value.  Besides, this document defines how Group OSCORE can be
   used to protect multicast notifications end-to-end from the CoAP
   server to the multiple observer clients.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 14, 2021.

Tiloca, et al.          Expires January 14, 2021                [Page 1]
Internet-Draft       Observe Multicast Notifications           July 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Server-Side Requirements  . . . . . . . . . . . . . . . . . .   5
     2.1.  Request . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Informative Response  . . . . . . . . . . . . . . . . . .   6
     2.3.  Notifications . . . . . . . . . . . . . . . . . . . . . .   8
     2.4.  Congestion Control  . . . . . . . . . . . . . . . . . . .   9
     2.5.  Cancellation  . . . . . . . . . . . . . . . . . . . . . .   9
       2.5.1.  Rough Counting of Clients in the Group Observation  .  10
   3.  Client-Side Requirements  . . . . . . . . . . . . . . . . . .  13
     3.1.  Request . . . . . . . . . . . . . . . . . . . . . . . . .  13
     3.2.  Informative Response  . . . . . . . . . . . . . . . . . .  14
     3.3.  Notifications . . . . . . . . . . . . . . . . . . . . . .  14
     3.4.  Cancellation  . . . . . . . . . . . . . . . . . . . . . .  15
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   5.  Protection of Multicast Notifications with Group OSCORE . . .  17
     5.1.  Signaling the OSCORE Group in the Informative Response  .  17
     5.2.  Server-Side Requirements  . . . . . . . . . . . . . . . .  19
       5.2.1.  Registration  . . . . . . . . . . . . . . . . . . . .  19
       5.2.2.  Informative Response  . . . . . . . . . . . . . . . .  20
       5.2.3.  Notifications . . . . . . . . . . . . . . . . . . . .  20
       5.2.4.  Cancellation  . . . . . . . . . . . . . . . . . . . .  21
     5.3.  Client-Side Requirements  . . . . . . . . . . . . . . . .  21
       5.3.1.  Informative Response  . . . . . . . . . . . . . . . .  21
       5.3.2.  Notifications . . . . . . . . . . . . . . . . . . . .  22
   6.  Example with Group OSCORE . . . . . . . . . . . . . . . . . .  22
   7.  Informative Response Parameters . . . . . . . . . . . . . . .  25
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  26