Performance Analysis of the Objective Functions in IPv6 Routing Protocol for LLN’s used in IOT Applications

The Internet of Things network consists of smart devices connected to each other and deployed in domains of Industrial Monitoring, Military, Automatic Meter reading, Environment, Home automation, Healthcare etc. The network here is classified as LLN (Low Power and Lossy Network) due to resource constraints and the noisy employment environment. The design of Routing Algorithm is a crucial factor governing the performance of LLN's. The RPL (IPv6 Routing protocol for LLN's), specially designed for LLN's, is proposed by IETF ROLL working group. This protocol aims to construct a Destination Oriented DAG using a set of parameters and constraints defined within the chosen Objective Function. The two standard OF's documented in this protocol are Minimum rank with Hysteresis Objective Function (MRHOF) and Objective Function zero (OF0). The selection of Objective Function during the network implementation impacts the formation of the DODAG and in turn influences crucial parameters like Power Consumption, Packet Delivery Ratio, Latency, Convergence time, Network Lifetime etc. This paper aims to evaluate the RPL performance with OF0 and MRHOF, using Contiki-2.7 OS based COOJA simulator, for light and medium density networks. The simulation results indicate that MRHOF out performs OF0 for networks up to 70 nodes with respect to Energy Consumption. Above 110 nodes performance of OF0 is seen to be comparable to MRHOF.