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

The information below is for an old version of the document
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 2016-01-04
State Start Chartering/Rechartering (Internal IESG/IAB Review) Rechartering
WG State Active
IESG Responsible AD Suresh Krishnan
Charter Edit AD Brian Haberman
Send notices to (None)

Charter
charter-ietf-6tisch-01-00

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 Timeslotted Channel Hopping (TSCH) mode was introduced in 2012 as an 
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 IEEE802.15.4 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.

IEEE802.15.4 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
IEEE802.15.4 standard. The extent of the problem space for the WG is 
one or more LLNs, possibly federated through a common backbone link 
via one or more LLN Border Routers (LBRs). The WG will rely on, and if 
necessary extend, existing mechanisms for authenticating LBRs.

Initially, the WG has limited its scope to distributed routing over a 
static schedule using the Routing Protocol for LLNs (RPL) on the resulting
network. This new charter allows for the dynamic allocation of cells and
their exchange between adjacent peers to accommodate the available bandwidth
to the variations of throughput in IP traffic. 

The WG will continue working on securing the join process and making that fit
within the constraints of high latency, low throughput and small frame sizes
that characterize IEEE802.15.4 TSCH.

Additionally, IEEE802.15.4 TSCH being a deterministic MAC, it is envisioned 
that 6TiSCH will benefit from the work of DetNet WG to establish the so-called
deterministic tracks. The group will define the objects and methods that need
to be configured, and provide the associated requirements to DetNet.

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

Work Items:
-----------

The group will:

- Produce a specification of the 6top sublayer that describes the protocol for
neighbor nodes to negotiate adding/removing cells. This work will leverage
cross participation from IEEE members including the IEEE 6TiSCH Interest Group
(IG 6T) to define protocol elements and associated frame formats.

- Produce a specification for a default 6top Scheduling Function including the
policy to enable distributed dynamic scheduling of timeslots for IP traffic.
This may include the capability for nodes to appropriate chunks of the
matrix without starving, or interfering with other 6TiSCH nodes. This
particular work will focus on IP traffic since the work on tracks is not yet
advanced enough to specify their requirements.

- Produce requirements to the DetNet WG, detailing 6TiSCH chunks and tracks,
and the data models to manipulate them from an external controller such
as a PCE.

- Produce a specification for a secure 6TiSCH network bootstrap, adapted
to the constraints of 6TiSCH nodes and leveraging existing art when possible.

- Keep updating the "6TiSCH architecture" that describes the design of 6TiSCH 
networks. This document highlights the different architectural 
blocks, signaling and data flows, including the operation of the network in 
the presence of multiple LBRs. The existing document will be augmented
to cover dynamic scheduling and application of the DetNet work but will not
be delivered within this round of chartering.

- 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. This work depends on the standardization of a
method to access management data resources in constrained devices, such as
proposed by CoMI or COOL.

Non-milestone work items:
-------------------------

The Working Group regularly organizes interoperability events with support from
ETSI (i.e., ETSI 6TiSCH Plugtests) to get feedback from implementers early on
in the standardization process, and produce better standards.