Embedded Guru

Transmission of IPV6 packets over LoWPAN devices was considered nearly impossible once because the MTU of IPV6 packets is 1280 bytes which is much larger than the MTU of IEEE 802.15.4 data link layer (127 bytes). So 6LoWPAN implements an adaptation layer between data link layer and network layer to support transmission of IPV6 packets over 802.15.4 . Main purpose of the adaptation layer is to fragment and reassemble the IPV6 packets. Routing in 6LOWPAN can be divided into two categories based on the decision taken either on adaptation layer or on the network layer. If the routing decision is taken under the adaptation layer it is Mesh Under. If the routing decision is taken on the network layer it is Route Over. Mesh Under:           In mesh under scheme, routing and forwarding are performed at link layer . To send a packet to a particular destination,the EUI 64 bit address or the 16 bit address is used and sent to the neighbour node  so t...

Characteristics of LoWPAN's are as follows: 1. Small packet size : Maximum physical layer packet size=127 bytes.                                 Maximum frame size at the media aceess control layer=102 octets                                Link-layer security imposes further overhead,which in the maximum case has                                   21  octets as overhead leaving 81 octets for data packets. 2. Support for both 16-bit short or IEEE 64-bit extended media access control addresses. 3.L ow Data rates :  Data rates --->Physical Layer                               250kbps  ---->2.4GHz             ...