IPv6 over the TSCH mode of IEEE 802.15.4e
charter-ietf-6tisch-00-01

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. The
   mapping to existing protocols (such as the Constrained Application Protocol,
   CoAP) will be investigated.

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.