IPv6 over the TSCH mode of IEEE 802.15.4e

The information below is for an older proposed charter
Document Proposed charter IPv6 over the TSCH mode of IEEE 802.15.4e WG (6tisch) Snapshot
Title IPv6 over the TSCH mode of IEEE 802.15.4e
Last updated 2013-09-12
State Start Chartering/Rechartering (Internal Steering Group/IAB Review) Rechartering
WG State Proposed
IESG Responsible AD Erik Kline
Charter Edit AD Ted Lemon
Send notices to Thomas Watteyne <watteyne@eecs.berkeley.edu>, Pascal Thubert <pthubert@cisco.com>



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
LLN 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 portion of the IEEE802.15.4 standard. It inherits
from long-standing industrial process control standards such as WirelessHART
and ISA100.11a, while significantly improving reliability, determinism, and
power comsumption.

The nodes in a IEEE802.15.4e TSCH network communicate by following a 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 front 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.
- Umbrella networks transporting data from different independent clients, and
for which an operator needs flow isolation and traffic shaping.
- Energy harvesting networks, 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 scope of the WG includes one or more LLNs, each one
connected to a backbone through one or more BackBone Routers (BBRs).

Initially, the WG will consider a framework to install a static schedule. In
this case, a node's schedule remains unchanged after the node is done joining a
network. The Routing Protocol for LLNs (RPL) is used on the resulting network.

If successful, the intent is to recharter to allow for dynamic schedules.
For example, an entity located on the backbone can centrally compute a dynamic
schedule for traffic to be switched by the timeslot sublayer. Alternatively,
the amount of timeslots scheduled between two neighbors may be adapted
dynamically to the amount of traffic routed between those two nodes.

The WG will interface with other IETF WGs, potentially including ROLL, 6Lo,
CoRE, 6MAN, LWIG, and other appropriate groups in the IETF Internet, Routing
and Security areas.

Work Items:

The group will:

1. Produce "Timeslot Management Methods and Formats" to describe how an entity
can manage the TSCH schedule on a 6TiSCH node, and query timeslot information
from that node. Metrics such as timeslot quality reports are in scope, but
the actual bindings to transport operation are not.

2. Produce "Minimal 6TiSCH Configuration" to define how to build a 6TiSCH network
using the Routing Protocol for LLNs (RPL). This document will assume a static
TSCH schedule, which can be either hardcoded, or learnt by a node when joining
the network, possibly in a format as defined by work item 1.

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

Non-milestone work items:

The Working Group may maintain a number of running, often-respun documents, 
that evolve as the technology is refined:
- 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.