IPv6 over Low-power Wireless Personal Area Networks is the name of a working group in the IETF and targeting the idea that IP should be applied to small low-power devices with limited communication and processing capabilities to participate in the IoT. 6LoWPAN combined the latest version of Internet Protocol (IPv6) and the Low-power Wireless Personal Area Networks (LoWPAN), where smaller devices with 6LoWPAN can communicate with 802.15.4 powered devices and other devices on an IP network to participate in IoT. 6LoWPAN is a low-power wireless mesh network where every node has its own IPv6 address, allowing it to connect directly to the Internet using open standards. 6LoWPAN defined mechanisms that allow IPv6 packets to be sent and received over IEEE 802.15.4 based networks like zigbee. IPv4 and IPv6 are the work horses for data delivery for LAN, MAN and WAN. However IEEE 802.15.4 devices provide sensing communication-ability in the wireless domain.
IPv6 nodes are assigned 128 bit IP addresses in a hierarchical manner, through an arbitrary length network prefix. IEEE 802.15.4 devices may use either of IEEE 64 bit extended addresses or 16 bit addresses that are unique within a PAN. There is also a PAN-ID for a group of physically collocated IEEE 802.15.4 devices. IPv6 nodes are geared towards attaining high speeds. Algorithms and protocols implemented at the higher layers such as TCP kernel of the TCP/IP are optimized to handle typical network problems such as congestion. In IEEE 802.15.4-compliant devices, energy conservation and code-size optimization remain at the top of the agenda.
6LoWPAN defines encapsulation and header compression methodology (standardized in RFC6282) allowing the normal IPv6 packets to interact with the 802.15.4 based networks on bidirectional ways with lower data rates. IPv6 is also compatible with smart grid devices to build a mesh network with IPv6 backbone. On the other hand, Thread is a IPv6-based protocol for IoT running over 6LoWPAN to enable home automation.
In technical comparison with Zigbee, interoperability means that the applications do not need to know the constraints of the physical links that carry their packets. ZigBee defines the communication between 802.15.4 nodes (Physical and Mac Layers) and then defines new upper layers all the way to the application. This means ZigBee devices can interoperate with other ZigBee devices, assuming they utilize the same profile. 6LoWPAN offers interoperability with other wireless 802.15.4 devices as well as with devices on any other IP network link with a simple bridge device that requires a more complex application layer gateway with an adaptation layer that allows transmission of IPv6 datagrams over 802.15.4 networks