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The 6LoWPAN concept originated from the idea that "the Internet Protocol could and should be applied even to the smallest devices," and that low-power devices with limited processing capabilities should be able to participate in the Internet of Things.
The 6LoWPAN group has defined encapsulation and header compression mechanisms that allow IPv6 packets to be sent and received over IEEE 802.15.4 based networks. IPv4 and IPv6 are the work horses for data delivery for local-area networks, metropolitan area networks, and wide-area networks such as the Internet. Likewise, IEEE 802.15.4 devices provide sensing communication-ability in the wireless domain. The inherent natures of the two networks though, are different.
The base specification developed by the 6LoWPAN IETF group is RFC 4944 (updated by RFC 6282 with header compression, and by RFC 6775 with neighbor discovery optimizations). The problem statement document is RFC 4919.
The target for IP networking for low-power radio communication are applications that need wireless internet connectivity at lower data rates for devices with very limited form factor. An example is automation and entertainment applications in home, office and factory environments. The header compression mechanisms standardized in RFC6282 can be used to provide header compression of IPv6 packets over such networks.
IPv6 is also in use on the smart grid enabling smart meters and other devices to build a micro mesh network before sending the data back to the billing system using the IPv6 backbone. Some of these networks run over IEEE 802.15.4 radios, and therefore use the header compression and fragmentation as specified by RFC6282.
Thread is an effort of over 50 companies to standardize on a closed-documentation, royalty-free protocol running over 6LoWPAN to enable home automation. It is to be launched in the second half of 2015. The protocol will most directly compete with Z-Wave and Zigbee IP.
As with all link-layer mappings of IP, RFC4944 provides a number of functions. Beyond the usual differences between L2 and L3 networks, mapping from the IPv6 network to the IEEE 802.15.4 network poses additional design challenges (see RFC 4919 for an overview).
Several routing protocol have been proposed by the 6LoWPAN community such as LOAD, DYMO-LOW, HI-LOW. However, only two routing protocols are currently legitimate for large-scale deployments: LOADng  standardized by the ITU  under the recommendation ITU-T G.9903 and RPL  standardized by the IETF ROLL working group.