6LoWPAN is an acronym for "IPv6 over Low power Wireless Personal Area Network" (English: IPv6 for WPAN with low energy consumption). 6LoWPAN is a communication protocol for wireless data transmission and a working group of the IETF, which is responsible for this standard.
The standard includes the possibility header compression method, which make it more efficient to transmit IPv6 packets over IEEE 802.15.4 based networks. The Internet Protocol is the basis for the network structures of the Internet and local networks. 6LoWPAN aims to integrate wireless PANs with little effort as possible into existing networks.
The basic specification of the protocol, which was developed by the 6LoWPAN working group of the IETF is held in RFC 4944. Some problems of 6LoWPAN are listed in RFC 4919. Since the header compression from the initial design ( HC1 ) in only a few cases leads to good results, a new method was introduced in RFC 6282 ( IPHC ) and the old will no longer be used.
6LoWPAN Adaptation Layer
The main component of the 6LoWPAN protocol is the 6LoWPAN adaptation layer that works on the switching level of the OSI model and tasks such as header compression, packet fragmentation and defragmentation, and routing takes over in mesh networks.
Of the 127 bytes of the maximum transmission unit (MTU) 25 used for the MAC layer. An optional additional layer, which is another 21 bytes for AES -CCM -128 encryption, remain only 81 bytes for the overlying layer. The IPv6 header requires 40 bytes, the UDP header further 8 bytes, thus only 33 bytes are available for user data. By Kompromierung IPv6 and UDP headers of the two 6LoWPAN headers can be compressed, in the ideal case, up to seven bytes.
Packet fragmentation and defragmentation
IPv6 requires an MTU of at least 1280 bytes. However, IEEE 802.15.4 provides only for a packet size of 127 bytes. The 6LoWPAN adaptation layer enables transparent fragmentation of IP packets so that these larger MTU is virtually available.
IP Routing in Meshed networks ( Meshes ) with mobile nodes raises two sub- problems:
- Update the routing tables through the ever-changing mesh
- To ensure the reachability of the IPv6 routing each node from the Internet
6LoWPAN offers the possibility to incorporate the routing through the mesh network. For this, a mesh header is placed in front of the compression and fragmentation header containing the start and end ID of the node and the number of remaining hops. This form of routing is called mesh under.
The start and end ID of the node is in mesh -under no IP address, but eg the MAC address of each node.
So information ( MAC address) of the data link layer and thus the area of network technology (IEEE 802.15.4 ) for the identification of nodes in the routing can be used. That's why the name mesh under- routing.
For mesh under special routing algorithms are being developed that take into account the mobility of the network nodes. One of the most common is the distance vector algorithm. In 6LoWPAN a simplified version of the AODV protocol is used in 6LoWPAN Ad hoc Routing Protocol (LOAD ), which is specified in RFC 3561.
More specific 6LoWPAN mesh routing protocols are DYMO ( Dynamic MANET On Demand) and HiLow ( hierarchical routing protocol for 6LoWPAN ).
A routing based on IP (network layer) is called route -over. Designed for 6LoWPAN RPL provides a way of the route- over.
In the area of open source:
- 6LoWPAN implementation in Linux
- 6LoWPAN implementation in Contiki
- BLIP: 6LoWPAN implementation in TinyOS
- 6LoWPAN implementation in RIOT
As a proprietary implementations:
- Nanostack and Nano Router Sensinode