Global Time Distribution in 6TiSCH Networks
draft-vilajosana-6tisch-globaltime-00

The information below is for an old version of the document
Document Type Active Internet-Draft (individual)
Last updated 2018-03-01
Stream (None)
Intended RFC status (None)
Formats plain text pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
6TiSCH                                                X. Vilajosana, Ed.
Internet-Draft                                                  P. Tuset
Intended status: Standards Track                             B. Martinez
Expires: September 2, 2018               Universitat Oberta de Catalunya
                                                                J. Munoz
                                                                   Inria
                                                           March 1, 2018

              Global Time Distribution in 6TiSCH Networks
                 draft-vilajosana-6tisch-globaltime-00

Abstract

   This specification defines an optional extension to the Join Response
   message defined by the Minimal Security Framework for 6TiSCH.  The
   extension aims at providing global time distribution support so nodes
   in the 6TiSCH network can exploit global time information instead of
   relying only in relative network time based on the Absolute Sequence
   Number (ASN).  The specification also defines a mechanism for
   resynchronization, to handle leap seconds or to enable periodic
   global time updates relying on a CoAP service.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

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
   working documents as Internet-Drafts.  The list of current Internet-
   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 September 2, 2018.

Vilajosana, et al.      Expires September 2, 2018               [Page 1]
Internet-Draft Global Time Distribution in 6TiSCH Networks    March 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Global Time Source  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Global Time Extension to the Join Response  . . . . . . . . .   4
   4.  Resynchronization . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Leap Second handling  . . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Time Synchronized Channel Hopping (TSCH) exploits node
   synchronization to build up deterministic access networks through
   scheduling [RFC7554].  6TiSCH defines a control plane architecture to
   enable IEEE802.15.4 TSCH networks to securely bootstrap and in a
   distributed manner self-organize in order to meet application traffic
   needs [I-D.ietf-6tisch-architecture].  The synchronization accuracy
   between the nodes' clocks in a 6TiSCH network is dependent on the
   network maintenance traffic (Keep Alives), application traffic, and
   MAC layer guard time duration.  It is well-known that the smaller the
   guard time, the smaller the tolerated drift between two nodes, and
   hence the more precise their synchronization.

   The concept of network synchronization is achieved through a virtual
   counter referred as Absolute Sequence Number (ASN).  In a 6TiSCH
   network, each node updates its ASN at every slot, giving the nodes
   the same notion of time (with timeslot granularity).  This time is
   relative to the moment the network started or reset and hence cannot
   be used to compare tagged events from different networks.

Vilajosana, et al.      Expires September 2, 2018               [Page 2]
Show full document text