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 PCLimited hardware resources: Low processing power (microcontroller/ dsp) Little memory Low powerLimited networks capabilities: Short range Low bitrate Message-Size
Usage scenarios Building automation Industrial automation Logistics Enviromental Monitoring Personal/ Health Monitoring Etc.
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 Mobility: Node Mobility and Network Mobility Reviewof Transport Layer Protocols: TCP inefficient for wireless embedded devices (wireless packet lost) Handleoffline 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)
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!
Compress IPv6 headers HC1: IP header HC2: UDP header Reduce header size by omissionOmit headers that... can be reconstructed from L2 layer headers (redundant) contain information not needed or used in the context (unnessecary)
HC1 – Compress IPv6 address IPv6 address: 64bit prefix | 64bit interface idRemove IPv6 address-prefix: All nodes in a PAN share single prefix PAN ID maps to IPv6 prefixRemove IPv6 Interface ID (IID) for local communication: IID generated from EUID64 (L2)
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/ BootstrappingHandle 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
Conclusion6LoWPAN... 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)
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