Routing Over Low power and Lossy networks
charter-ietf-roll-03

Low power and Lossy networks (LLNs) are made up of many
embedded devices with limited power, memory, and processing
resources. They are interconnected by a variety of links, such as
IEEE 802.15.4, Bluetooth, Low Power WiFi, wired or other low
power PLC (Powerline Communication) links. LLNs are transitioning
to an end-to-end IP-based solution to avoid the problem of
non-interoperable networks interconnected by protocol translation
gateways and proxies.

Generally speaking, LLNs have at least five distinguishing
characteristics:
- LLNs operate with a hard, very small bound on state.
- In most cases, LLN optimize for saving energy.
- Typical traffic patterns are not simply unicast flows (e.g. in some
cases most if not all traffic can be point to multipoint).
- In most cases, LLNs will be employed over link layers with
restricted frame-sizes, thus a routing protocol for LLNs should be
specifically
adapted for such link layers.
- LLN routing protocols have to be very careful when trading off
efficiency for generality; many LLN nodes do not have resources to
waste.

These specific properties cause LLNs to have specific routing
requirements.

Existing routing protocols such as OSPF, IS-IS, AODV, and OLSR have
been evaluated by the working group and have in their current form been
found to not satisfy all of these specific routing requirements.

The Working Group is focused on routing issues for LLN.

There is a wide scope of application areas for LLNs, including
industrial monitoring, building automation (HVAC, lighting, access
control,
fire), connected homes, healthcare, environmental monitoring, urban sensor
networks (e.g. Smart Grid), asset tracking. The Working Group focuses
on routing solutions for a subset of these: industrial, connected
home, building and urban sensor networks for which routing requirements have
been specified. These application-specific routing requirement
documents will be used for protocol design.

The Working Group focuses only on IPv6 routing architectural framework
for these application scenarios. The Framework will take into
consideration various aspects including high reliability in the presence
of time
varying loss characteristics and connectivity while permitting low-power
operation with very modest memory and CPU pressure in networks
potentially comprising
a very large number (several thousands) of nodes.

The Working Group will pay particular attention to routing security
and manageability (e.g., self routing configuration) issues. It will
also need to consider the transport characteristic the routing protocol
messages will experience. Mechanisms that protect an LLN from congestion
collapse or
that establish some degree of fairness between concurrent
communication sessions are out of scope of the Working Group. It is
expected that
upper-layer applications utilizing LLNs define appropriate mechanisms.
The solution must include unicast and multicast considerations.

Work Items:

• Specification of routing metrics used in path calculation. This
  includes static and dynamic link/node attributes required for routing in
  LLNs.

• Provide an architectural framework for routing and path selection at
  Layer 3 (Routing for LLN Architecture) that addresses such issues as
  whether LLN routing require a distributed and/or centralized path
  computation models, whether additional hierarchy is necessary and how it
  is
  applied.

Manageability will be considered with each approach, along with
various trade-offs for maintaining low power operation, including the
presence of non-trivial loss and networks with a very large number of nodes.

• Produce a routing security framework for routing in LLNs.

• Protocol work: The Working Group will consider specific routing
  requirements from the four application documents collectively, and
  specify either
  a new protocol or extend an existing routing protocol in cooperation
  with the
  relevant Working Group.
  If requirements from the four target application areas cannot be met
  with a single protocol, the WG may choose to specify or extend more than
  one
  protocol (this will require a recharter of the WG).

• Documentation of applicability statement of ROLL routing protocols.