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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)