Although routing is among the key issues of 6LoWPAN research, the way to encapsulate a new routing header in the 6LoWPAN packet has yet been investigated thoroughly. In this paper, different ways of routing header encapsulation in 6LoWPAN protocol stack is discussed. The simplified version Ad-Hoc On-Demand Distance Vector (AODV) such as On-Demand Distance Vector (LOAD) and Dynamic MANET On-demand for 6LoWPAN (DYMO-low) have currently been proposed in 6LoWPAN routing. Hierarchical routing (HiLow) is another routing protocol that is used in 6LoWPAN to increase the network scalability. Some comparisons of these routing protocols have been made in terms of their routing metric such as number of hops count. The used control messages for the route discovery in different routing protocols have also been investigated. These comparisons show that each routing protocol has its own advantage depends on the involved applications. There are some tradeoffs of respective routing protocols. The routing protocol that uses hello message may provide more reliable but results a higher delay in the packet routing.

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The feature of 6LoWPAN is the capability of the dynamic assignment of 16-bit short addresses. Hierarchical routing (HiLow) algorithm that uses dynamically assigned 16-bit unique short address as its interface identifier has an advantage of memory saving. The 16-bit unique short address is assigned to a 6LoWPAN device during an association operation with a neighbor node which is also called parent node in HiLow. Besides reducing the overhead of maintaining routing table, HiLow also supports for larger scalability. However, previous research did not deal with the path recovery when sensor nodes in HiLow are failed. The node failure may be due to the battery lifetime of the 6LoWPAN device. This kind of failure will cause the expiration of the association event and make the previously assigned 16-bit short address of the child node from the failure parent node become invalid within PAN. In this paper, a new path recovery mechanism so-called step parent node (SPN) algorithm is proposed to conventional HiLow to reassign the valid 16-bit short addresses for the child nodes of the failure parent node and provide the path robustness. The child nodes of the failure parent node will broadcast a step parent node request message (spn_request) to the neighbor nodes. The neighbor node whose child nodes do not exceed the maximum child value will act as a step parent node of the new child nodes. It enhances the reliability of conventional hierarchical routing mechanism.

6LoWPAN has become a new technology to provide the internet connectivity to the traditional WSN. The introduction of 6LoWPAN adaptation layer enables the smooth delivery of packet from network layer to MAC layer. In this paper, the LOAD-based routing protocol with the proposed originator recognition (OR) path recovery mechanism is introduced. The proposed OR path recovery mechanism modifies the IETF conceptual LOAD protocol message by inserting an identity key in the generated RERR message. The identity key is then used by the originator of a failed data packet to initialize path recovery during the link failure. The developed OR-LOAD has examined under the 6LoWPAN environment in Qualnet simulator. Its performance is evaluated and compared to AODV in terms of packet delivery ratio and throughput.

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