The ETX Objective Function for RPL

The ETX metric of a wireless link is the expected number of transmissions required to successfully transmit and acknowledge a packet on the link. The Routing Protocol for Low Power and Lossy Networks (RPL) allows the use of objective functions to construct routes that optimize or constrain a routing metric on the paths. This specification describes ETXOF, an objective function that minimizes ETX. The RPL path computation using ETXOF results in minimum-ETX paths from the nodes to the DAG roots, i.e., paths that minimize the number of packet transmissions for packet delivery from nodes in the network to the DAG root.