6loWPAN

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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 paragon that is aimed at allowing IPv6 packets to be sent to and received from PANs, more specifically over IEEE802.15.4-standard based networks. IPv6 is the work horse for data delivery for wired networks—the internet. Likewise, IEEE802.15.4 devices provide sensing communication-ability in the wireless domain. The inherent natures of the two networks is different—so much so that a working group has been chartered under the auspices of the IETF. Another wiki site, called 6lowpan.tzi.org keeps track of latest developments at the 6lowpan working group of IETF. Another website www.6lowpan.org shows the research efforts for demonstrating 6lowpan testbed.

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[edit] Application areas

6lowpans target 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.

[edit] Problems

IPv6 network and IEEE802.15.4 network are two totally different networks. All the design challenges for 6lowpan arise from this difference fundamentally. Some of the problems are the following Difference in packet sizes of the two networks IPv6 defines a maximum transmission unit (MTU) of 1280 Bytes. Vice versa, for IEEE802.15.4 a packet size of 127 octets is standardized. 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.

[edit] Orthogonal addressing schemes

IPv6 nodes are assigned 128 bits 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.

[edit] Differing device designs

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

[edit] 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 to be at the top of the agenda.

[edit] 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 6lowpan bandwagon. All the research areas aim to address the problems that restrain its smooth realization.

[edit] Adaptation layer for interoperability and packet formats

An adaptation mechanism to allow interoperability between IPv6 domain and the IEEE802.15.4 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. 6lowpan format document proposes an adaptation layer that carries out the functionality of the adaptation layer.

[edit] 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. A suggestive mechanism has been put forth in the 6lowpan format document.

[edit] 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. And the routability of packets to/from the IPv6 domain from/to the PAN domain. Some of the routing protocols currently being developed by the 6lowpan community are LOAD, DYMO-low, and Hi-Low.

[edit] Device and service discovery

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

[edit] Status of the working group

A number of internet drafts have been proposed thus far. The latest information about the goals and milestones of the working group, and the considerations for their recharterting can be found at the 6lowpan site of the IETF.

[edit] External links

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