IPv6 over the TSCH mode of IEEE 802.15.4e
charter-ietf-6tisch-00-03

6TiSCH: "IPv6 over the TSCH mode of IEEE 802.15.4e".

Background/Introduction:

Low-power and Lossy Networks (LLNs) interconnect a possibly large
number of resource-constrained nodes to form a wireless mesh
network. The 6LoWPAN, ROLL and CoRE IETF Working Groups have defined
protocols at various layers of the protocol stack, including an IPv6
adaptation layer, a routing protocol and a web transfer protocol. This
protocol stack has been used with IEEE802.15.4 low-power radios.

The IEEE802.15.4e Timeslotted Channel Hopping (TSCH) is a recent
amendment to the Medium Access Control (MAC) portion of the
IEEE802.15.4 standard. TSCH is the emerging standard for industrial
automation and process control LLNs, with a direct inheritance from
WirelessHART and ISA100.11a. Defining IPv6 over TSCH, 6TiSCH is a key
to enable the further adoption of IPv6 in industrial standards and the
convergence of Operational Technology (OT) with Information Technology
(IT).

The nodes in a IEEE802.15.4e TSCH network communicate by following a
Time Division Multiple Access (TDMA) schedule. A timeslot in this
schedule provides a unit of bandwidth that is allocated for
communication between neighbor nodes. The allocation can be programmed
such that the predictable transmission pattern matches the traffic.
This avoids idle listening, and extends battery lifetime for
constrained nodes. Channel-hopping improves reliability in the
presence of narrow-band interference and multi-path fading.

These techniques enable a new range of use cases for LLNs, including:

• Control loops in a wireless process control network, in which high
  reliability and a fully deterministic behavior are required.

• Service Provider networks transporting data from different
  independent clients, and for which an operator needs flow isolation
  and traffic shaping.

• Networks comprising energy harvesting nodes, which require an
  extremely low and predictable average power consumption.

IEEE802.15.4e only defines the link-layer mechanisms. It does not
define how the network communication schedule is built and matched to
the traffic requirements of the network.

Description of Working Group:

The Working Group will focus on enabling IPv6 over the TSCH mode of
the IEEE802.15.4e standard. The extent of the problem space for the WG
is one or more LLNs, eventually federated through a common backbone
link via one or more LLN Border Routers (LBRs).

Initially, the WG will limit its scope to distributed routing over a
static schedule. In that case, a node's schedule can be either
preconfigured, or learnt by a node when joining the network, but it
remains unchanged after the node has joined a network. The Routing
Protocol for LLNs (RPL) is used on the resulting network.

The WG will interface with other appropriate groups in the IETF
Internet, Operations and Management, Routing and Security areas.

Work Items:

The group will:

1. Produce "6TiSCH architecture" to describe the design of 6TiSCH
   networks. This document will highlight the different architectural
   blocks and signalling flows, including the operation of the network
   in the presence of multiple LBRs. Initially, the document will
   focus on distributed routing operation over a static TSCH schedule.

2. Produce an Information Model containing the management requirements
   of a 6TiSCH node. This includes describing how an entity can manage
   the TSCH schedule on a 6TiSCH node, and query timeslot information
   from that node. A data model mapping for an existing protocol (such
   as Concise Binary Object Representation (CBOR) over the Constrained
   Application Protocol (CoAP)) will be provided.

3. Produce "Minimal 6TiSCH Configuration" defining how to build a
   6TiSCH network using the Routing Protocol for LLNs (RPL) and a
   static TSCH schedule. It is expected that RPL and the Objective
   Function 0 (OF0) will be reused as-is. The work will include a
   best practice configuration for RPL and OF0 operation over the
   static schedule. Based on that experience the group may produce a
   requirements draft for OF0 extensions, to be studied in ROLL.

Non-milestone work items:

The Working Group may maintain a number of running, often-respun
documents, that evolve as the technology is refined for work items
that do not affect the milestone work items:

• implementers guide: this document will collect clarifying
  information based on input from implementers, in particular as it
  becomes available from interoperability events. This guide will
  contain information about test harnesses used for interoperability
  testing.

• coexistence guide: this document will provide information on how
  6TiSCH can be operated in an environment shared with other protocols
  that use the same or a similar TSCH MAC, and/or operate on the same
  frequency band.

The WG will welcome requirements for dynamic timeslot operation, for
example for centralized schedule computation.