The Internet of Things and 6LoWPAN networks

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The Internet of Things allow communications and data sharing from mobile phones, industrial/building automation, logistics, personal sensors, etc. It uses the IP network which provides a simple and ubiquitous interaction between devices and an increasing interaction with the services provided.

6LoWPAN working group of IETF is researching on Low-power RT with IPv6: The Wireless Embedded Internet. 6LoWPAN has a broad range of applications:

6LoWPAN

6LoWPAN is the acronym of a working group in IETF who provides IPv6 over Low-Power Wirelles Area Networks. They stateless header compression, enable a standard socket API, minimize the usage of code and memory and alow direct end-to-end Internet integration whith multiple topology options.

By communicating natively with IP, LoWPAN networks are connected to other IP networks simply by using IP routers. LoWPANs will typically operate on the edge, acting as stub networks. The LoWPAN may be connected to other IP networks through one or more border routers that forward IP datagrams between different media.

6LoWPAN introduce an adaptation layer that enables efficient IPv6 communication over IEEE 802.15.4 LoWPAN links. Because of that, 6LoWPAN format defines how IPv6 communication is carried in 802.15.4 frames and specifies the adaptation layer’s key elements:

  • Header compression: IPv6 header fields are compressed by assuming usage of common values. Header fields are elided from a packet when the adaptation layer can derive them from link-level information carried in the 802.15.4 frame or based on simple assumptions of shared context. 40Bytes of IPv6 header are compressed into 2 Bytes of 6LowPAN header.

  • Fragmentation: IPv6 packets are fragmented into multiple link-level frames to accommodate the IPv6 minimum MTU requirement. 1280 Bytes of IPv6 frame (minimum IPv6 MTU) have been fragmented to 127Bytes, which is the  802.15.4 MTU.


  • Layer-two forwarding: To support layer-two forwarding of IPv6 datagrams, the adaptation layer can carry link-level addresses for the ends of an IP hop. Mesh Addressing header is used to forward 6LoWPAN playloads over multiple radio hops and support layer-two forwarding and includes the Hop Limit, Source Adrress and Destination Adress.

RPL

RPL is a routing protocol over low-power and lossy networks like 6LoWPAN. It’s very useful in urban networks (including Smart Grid applications) and in building, industrial and home automation. DODAG (Destination Oriented Directed Acyclic Graph) is specified  to use in LLNs (Low Power and Lossy Networks) and support traffic with very different requirements in terms of path quality (poor, fair and good).

Nowadays, several groups are working on 6LoWPAN networking. ISA100 group, for example, is working to standardize wireless systems for automation.

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