6LoWPAN Martin Abraham

6LoWPAN   IPv6 over Low Power Wireless Area Networks

  Level 2/3 Protocol (OSI)

  Enables usage of IPv6 by wireless embedded devices

  Described in IETF RFC 4919, 4944

Device characteristics   Dedicated to specific task/ not general purpose like PC

Limited hardware resources:

  Low processing power (microcontroller/ dsp)

  Little memory Low power

Limited networks capabilities:

  Short range Low bitrate Message-Size

Usage scenarios   Building automation

  Industrial automation

  Logistics

  Enviromental Monitoring

  Personal/ Health Monitoring

  Etc.

Personal Monitoring

Industrial Automation

Home Automation

Protocol history   1980s: Cabled networking

- not everthing can be cabled - expensive

  Mid 1990s: ~ 20 proprietary solutions (Z-Wave) - scalibility - no interoperability (vendor lock) - bound to specific data-link layer

  2003+: ZigBee (IEEE 802.15.4 based) + first wireless standard - scalability (small scale isolated ad hoc networking) - bound to specific data-link layer - not long-lived (quick changes)

Why IPv6?   Long-lived technology (20 years+)

  Ability to connect heterogeneous networks

  Existing worldwide free-to-use infrastructure

  Global scalability

  2^128 Bit (16 Byte) Addressing = Enough for Internet of Things

  Great number of tools (diagnostic, management etc.)

IPv6 Problems   Bandwidth and Energy efficiency

Standard protocol: IEEE 802.15.4 L1/L2 (low bandwidth: 250 kbps, low power: 1mW)

  Fragmentation: IPv6 minimum frame size (MTU) = 1280 bytes IEEE 802.15.4 frame size (MTU) = 127 byte (higher bit error rate, failure proneness)

  Header compression: IPv6 headers (40 bytes) reduce payload 53 byte payload in 127 byte 802.15.4 frame

IPv6 Problems   Mobility:

Node Mobility and Network Mobility

  Review of Transport Layer Protocols: TCP inefficient for wireless embedded devices (wireless packet lost)

  Handle offline devices: IP assumes devices are always on, but embedded devices may not (power and duty cycles)

  Multicast support: IEEE 802.15.4 & other radios do not support Multicast (expensive)

6LoWPAN

Fragmentation   Datagram = Basic transfer unit (header, payload)

  3 fragmentation header

Fragmentation   Datagram-size: 11bit = 2047 > 1280byte (mininmal IP MTU)

Transmitted in every fragment. Destination can reserve memory on first arrival for the whole message

  Datagram-tag: 16 bit Sufficient for limited link speed (min. 4 min for repeat)

  Datagram-offset: 8 bit Offset addressed in 8byte units 2047bytes addressable by 8 bit

  Longer messages? Fragmentation handled by standard ip fragmentation (L3) awsome!

Header compression

Compress IPv6 headers   HC1: IP header

  HC2: UDP header

  Reduce header size by omission

Omit headers that...

  can be reconstructed from L2 layer headers (redundant)

  contain information not needed or used in the context (unnessecary)

IPv6 header (6LoWPAN header)

HC1 – Compress IPv6 address   IPv6 address: 64bit prefix | 64bit interface id

Remove IPv6 address-prefix:

  All nodes in a PAN share single prefix

  PAN ID maps to IPv6 prefix

Remove IPv6 Interface ID (IID) for local communication:

  IID generated from EUID64 (L2)

6LoWPAN Architecture

Mobility   Micro-Mobility:

stay in same ip-domain e.g. switch edge router inside extended 6LoWPAN network

  Node-Mobility: Node moves physically between different 6LoWPAN networks e.g. attached to a parcel

  Network-Mobility: Full 6LoWPAN networks switches backhaul link handled by edge router

Communication/ Bootstrapping Handle offline devices:

  Node-initiated communication (to deal with sleep cycles etc.)

Bootstrapping/ Multicast/ device constraints:

  Roles: Router, Nodes, NEW: Edge Router (take load of devices)

  Node Registration/ Node Confirmation replaces Multicast

  Duplicate Address Detection done by Edge Router

Conclusion 6LoWPAN...

  is an open standard

  provides an adapter between IEEE 802.15.4 (L1/2) and IPv6 (L3)

  enables interoperability between wireless embedded devices (and common Internet devices) using standard protocols

  fosters standardization of communication in scope of wireless embedded devices

  provides an important foundation for the Internet of Things (IoT)