6LoWPAN

6lowpan is an acronym of "IPv6 over Low power Wireless Personal Area Networks". 6lowpan is the name of the working group in the internet area of IETF. 6lowpan is the coupling that is aimed at allowing IPv6 packets to be sent to and received from Personal Area Networks, more specifically over IEEE 802.15 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, is different.

Application areas

The target for 6lowpan are the applications that need wireless internet connectivity at lower data rates for devices with very limited form factor. Examples could include, but are not limited to: automation and entertainment applications in home, office and factory environments. Although such applications can be rendered in an autonomous fashion, providing internet connectivity can let the designers offer the same services with untethered value-addition.

6LoWPAN is handled as a key-technology for Smart Objects.

Problems

IPv6 network and IEEE802.15.4 network are two totally different networks. All the design challenges for 6lowpan arise from these fundamental differences.

Difference in packet sizes of the two networks

IPv6 defines a maximum transmission unit (MTU) of 1280 Bytes. In contrast, IEEE802.15.4'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.

Orthogonal addressing schemes

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 IEEE802.15.4 devices.

Differing device designs

IEEE802.15.4 devices are intentionally constrained in form factor to reduce costs. On the other hand, wired nodes in the IP domain are usually connected to sources of infinite power supply.

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 IEEE802.15.4-compliant devices, energy conservation and code-size optimization remain at the top of the agenda.

Research areas

As the application market for 6lowpan is becoming ripe, more interest is being generated into 6lowpan research. Scientists, academicians, students, businessmen, developers, and service providers are all trying to join the bandwagon. All the research areas aim to address the problems that restrain its smooth realization.

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 IEEE802.15.4 is cumbersome, if not exhaustingly complex.

Routing considerations and protocols for mesh topologies in 6lowpans

Routing per se is a two phased problem that is being considered for the 6lowpan:

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

Device and service discovery

Since 6lowpan devices may result in the formation of ad hoc networks, the current state of neighboring devices and the services hosted by such devices will need to be known. 6lowpan neighbour discovery extensions is an internet draft proposed as a contribution in this area.

External links

* [http://www.ietf.org/ Internet Engineering Task Force (IETF)]
* [http://vesuvio.ipv6.cselt.it/internet-drafts/draft-daniel-6lowpan-hilow-hierarchical-routing-00.txt Hierarchical Routing over 6lowpan (HiLow)]
* [http://carmen.cselt.it/internet-drafts/draft-daniel-6lowpan-interoperability-01.txt Interoperability of 6lowpan]
* [http://tools.ietf.org/wg/6lowpan/draft-daniel-6lowpan-load-adhoc-routing-02.txt 6lowpan Ad Hoc On-Demand Distance Vector Routing (LOAD)]
* [http://carmen.cselt.it/internet-drafts/draft-montenegro-6lowpan-dymo-low-routing-00.txt Dynamic MANET On-demand for 6lowpan (DYMO-low) Routing]
* [http://tools.ietf.org/id/draft-chakrabarti-6lowpan-ipv6-nd-01.txt LowPan Neighbor Discovery Extensions]
* [http://tools.ietf.org/id/draft-sarikaya-6lowpan-forwarding-00.txt Serial forwarding approach to connecting TinyOS-based sensors to IPv6]
* [http://www.ietf.org/html.charters/6lowpan-charter.html 6lowpan Working Group]
* [http://6lowpan.tzi.org 6lowpan.tzi.org]
* [http://www.6lowpan.org www.6lowpan.org]

Routing protocols under development

* [http://daniel.vsix.net/ietf/6lowpan/draft-daniel-6lowpan-load-adhoc-routing-02.txt LOAD]
* [http://carmen.cselt.it/internet-drafts/draft-montenegro-6lowpan-dymo-low-routing-00.txt DYMO-low]
* [http://vesuvio.ipv6.cselt.it/internet-drafts/draft-daniel-6lowpan-hilow-hierarchical-routing-00.txt Hi-Low]