6LoWPAN (IPv6 over Low-Power Wireless Personal Area Networks)[1] was a working group of theInternet Engineering Task Force (IETF).[2] It was created with the intention of applying theInternet Protocol (IP) even to the smallest devices,[3] enabling low-power devices with limited processing capabilities to participate in theInternet of Things.[1]
The 6LoWPAN group defined encapsulation, header compression, neighbor discovery and other mechanisms that allow IPv6 to operate overIEEE 802.15.4 based networks. AlthoughIPv4 and IPv6 protocols do not generally care about thephysical andMAC layers they operate over, the low-power devices and small packet size defined by IEEE 802.15.4 make it desirable to adapt to these layers.[4]
The base specification developed by the 6LoWPAN IETF group isRFC 4944 (updated byRFC 6282 with header compression,RFC 6775 withneighbor discovery optimization,RFC 8931 with selectivefragment recovery and with smaller changes inRFC 8025 andRFC 8066). The problem statement document isRFC 4919. IPv6 overBluetooth Low Energy using 6LoWPAN techniques is described inRFC 7668.
The targets for IPv6 networking for low-power radio communication are devices that needwireless connectivity to many other devices at lowerdata rates for devices with very limited power consumption. The header compression mechanisms inRFC 6282 are used to allow IPv6 packets to travel over such networks.
IPv6 is also in use on thesmart grid enablingsmart 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.[citation needed]
Thread is a standard from a group of more than fifty companies for a protocol running over 6LoWPAN to enablehome automation. The specification is available at no cost as of 24 June 2022[update], but paid membership is required to implement the protocol.[5][6] Version 1.0 of the specification was published on 2015-10-29.[5] The protocol most directly competes withZ-Wave andZigbee IP.[7] In IoT device communications using theMatter standard, Thread is one of two possible wireless transport layers.
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 (seeRFC 4919 for an overview).
IPv6 requires thelinkmaximum transmission unit (MTU) to be at least 1280octets.[8] In contrast, IEEE 802.15.4's standardframe size is 127 octets. A maximum frame overhead of 25 octets and an optional but highly recommended security feature at thelink layer poses an additional overhead of up to 21 octets are forAES-CCM-128. This leaves only 81 octets for the upper layers. Since this is so much less than 1280, 6LoWPAN defines a fragmentation and reassembly layer. Further, the standard IPv6 Header is 40 octets long, so header compression is defined as well.
IPv6 nodes are assigned 128 bitIP 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, after an association event, 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.
IEEE 802.15.4 devices are intentionally constrained in form factor to reduce costs (allowing for large-scale network of many devices), reduce power consumption (allowing battery powered devices) and allow flexibility of installation (e.g. small devices for body-worn networks). On the other hand, wired nodes in the IP domain are not constrained in this way; they can be larger and make use of mains power supplies.
IPv6 nodes are geared towards attaining high speeds.Algorithms andprotocols implemented at the higher layers such as TCP kernel of theTCP/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.
An adaptation mechanism to allow interoperability between IPv6 domain and the IEEE 802.15.4 can best be viewed as a layer problem. Identifying the functionality of this layer and defining newer packet formats, if needed, is an enticing research area.RFC 4944 proposes an adaptation layer to allow the transmission of IPv6 datagrams over IEEE 802.15.4 networks.
The management of addresses for devices that communicate across the two dissimilar domains of IPv6 and IEEE 802.15.4 is cumbersome, if not exhaustingly complex.
Routing per se is a two phased problem that is being considered for low-power IP networking:
Several routing protocols have been proposed by the 6LoWPAN community such as LOAD,[9] DYMO-LOW,[10] HI-LOW.[11] However, only two routing protocols are currently legitimate for large-scale deployments: LOADng[12] standardized by theITU under the recommendationITU-T G.9903 andRPL[13] standardized by the IETF ROLL working group.[14]
Since IP-enabled devices may require the formation ofad hoc networks, the current state of neighboring devices and the services hosted by such devices will need to be known. IPv6 neighbour discovery extensions is aninternet draft proposed as a contribution in this area.
IEEE 802.15.4 nodes can operate in either secure mode or non-secure mode. Twosecurity modes are defined in the specification in order to achieve different security objectives: Access Control List (ACL) and Secure mode[15]
IPv6 requires that every link in the internet have an MTU of 1280 octets or greater.