6LoWPAN

6LoWPAN is an acronym of IPv6 over Low -Power Wireless Personal Area Networks.[1] 6LoWPAN is the name of a concluded working group in the Internet area of the IETF.[2]

The 6LoWPAN concept originated from the idea that "the Internet Protocol could and should be applied even to the smallest devices,"[3] and that low-power devices with limited processing capabilities should be able to participate in the Internet of Things.[4]

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. IPv6 over Bluetooth Low Energy (BLE) is defined in RFC 7668.

Application areas

The target for IP networking for low-power radio communication is 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

Thread is an effort of over 50 companies to standardize on a protocol running over 6LoWPAN to enable home automation. The specification is available at no cost as of 7 May 2018, subject to adherence to an EULA stipulating that Thread Group membership (in most cases paid) is required to implement the protocol.[5][6] It is to be launched in the second half of 2015.[7] The protocol will most directly compete with Z-Wave and Zigbee IP.[8]

Connected Home over IP

Connected Home over IP is the latest effort to standardize on a protocol running over 6LoWPAN to enable home automation, by combining it with DTLS , CoAP and MQTT-SN

Functions

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).

Adapting the packet sizes of the two networks

IPv6 requires the maximum transmission unit (MTU) to be at least 1280 octets. In contrast, IEEE 802.15.4's standard packet size is 127 octets. A maximum frame overhead of 25 octets spares 102 octets at the media access control layer. An optional but highly recommended security feature at the link layer poses an additional overhead. For example, 21 octets are consumed for AES-CCM-128 leaving only 81 octets for upper layers.

Address resolution

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, 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.

Differing device designs

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.

Differing focus on parameter optimization

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.

Adaptation layer for interoperability and packet formats

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.

Addressing management mechanisms

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 considerations and protocols for mesh topologies in 6LoWPAN

Routing per se is a two phased problem that is being considered for low-power IP networking:

  • Mesh routing in the personal area network (PAN) space.
  • The routability of packets between the IPv6 domain and the PAN domain.

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 the ITU under the recommendation ITU-T G.9903 and RPL[13] standardized by the IETF ROLL working group.[14]

Device and service discovery

Since IP-enabled devices may require the formation of ad 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 an internet draft proposed as a contribution in this area.

Security

IEEE 802.15.4 nodes can operate in either secure mode or non-secure mode. Two security modes are defined in the specification in order to achieve different security objectives: Access Control List (ACL) and Secure mode[15]

Further reading

See also
  • DASH7 active RFID standard
  • MyriaNed low power, biology inspired, wireless technology
  • Z-Wave designed to provide, reliable, low-latency transmission of small data packets at data rates up to 100kbit/s
  • ZigBee standards-based protocol based on IEEE 802.15.4.
  • LoRaWAN allows low bit rate communication from and to connected objects, thus participating to Internet of Things, machine-to-machine M2M, and smart city.
  • Thread (network protocol) standard suggested by Nest Labs based on IEEE 802.15.4 and 6LoWPAN.
  • Static Context Header Compression (SCHC)

References
  1. In 6LoWPAN: The Embedded Internet (Wiley, 2009), Shelby and Bormann redefine the 6LoWPAN acronym as "IPv6 over lowpower wireless area networks," arguing that "Personal" is no longer relevant to the technology.
  2. "IPv6 over Low power WPAN (6lowpan)". IETF. Retrieved 10 May 2016.
  3. Mulligan, Geoff, "The 6LoWPAN architecture", EmNets '07: Proceedings of the 4th workshop on Embedded networked sensors, ACM, 2007
  4. Zach Shelby and Carsten Bormann, "6LoWPAN: The wireless embedded Internet - Part 1: Why 6LoWPAN?" EE Times, May 23, 2011
  5. Thread 1.1 Specification
  6. Thread Group
  7. Higginbotham, Stacey. "This week's podcast unravels the secrets of Thread and HomeKit". gigaom.com. gigaom. Retrieved 30 January 2015.
  8. Sullivan, Mark. "Nest, Samsung, ARM and others launch 'Thread' home automation network protocol". venturebeat.com. venture beat. Retrieved 30 January 2015.
  9. Kim, K.; Daniel Park, S.; Montenegro, G.; Yoo, S.; Kushalnagar, N. (June 2007). 6LoWPAN Ad Hoc On-Demand Distance Vector Routing (LOAD). IETF. I-D draft-daniel-6lowpan-load-adhoc-routing-03. Retrieved 10 May 2016.
  10. Kim, K.; Montenegro, G.; Park, S.; Chakeres, I.; Perkins, C. (June 2007). Dynamic MANET On-demand for 6LoWPAN (DYMO-low) Routing. IETF. I-D draft-montenegro-6lowpan-dymo-low-routing-03. Retrieved 10 May 2016.
  11. Kim, K.; Yoo, S.; Daniel Park, S.; Lee, J.; Mulligan, G. (June 2007). Hierarchical Routing over 6LoWPAN (HiLow). IETF. I-D draft-daniel-6lowpan-hilow-hierarchical-routing-01. Retrieved 10 May 2016.
  12. Clausen, T.; Colin de Verdiere, A.; Yi, J.; Niktash, A.; Igarashi, Y.; Satoh, H.; Herberg, U.; Lavenu, C.; Lys, T.; Dean, J. (January 2016). The Lightweight On-demand Ad hoc Distance-vector Routing Protocol - Next Generation (LOADng). IETF. I-D draft-clausen-lln-loadng-14. Retrieved 10 May 2016.
  13. Winter, T.; Thubert, P.; Brandt, A.; Hui, J.; Kelsey, R.; Levis, P.; Pister, K.; Struik, R.; Vasseur, JP.; Alexander, R. (March 2012). RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks. IETF. doi:10.17487/RFC6550. RFC 6550. Retrieved 10 May 2016.
  14. "Routing Over Low power and Lossy networks (roll)". IETF. Retrieved 10 May 2016.
  15. Park, S.; Kim, K.; Haddad, W.; Chakrabarti, S.; Laganier, J. (March 2011). IPv6 over Low Power WPAN Security Analysis. IETF. I-D draft-daniel-6lowpan-security-analysis-05. Retrieved 10 May 2016.
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