Optimized link state routing for quality-of-service provisioning: Implementation, measurement, and performance evaluation

This paper provides a measurement-based performance evaluation of the Optimized Link State Routing (OLSR) protocol. Two versions of OLSR, OLSR-ETX and OLSR-ETT, are implemented and evaluated on a mesh network that we built from off-the-shelf commercial components and deployed within our department building. OLSR-ETX uses the Expected Transmission Count (ETX) metric, whereas OLSR-ETT uses the Expected Transmission Time (ETT) metric as a means of assessing link quality. The paper describes our implementation process of the ETT metric using the plug-in feature of OLSRd, and our calculation method of link bandwidth using the packet-pair technique. A series of measurements are conducted in our testbed to analyze and compare the performance of ETX and ETT metrics deemed useful for quality of service. Our measurements show that OLSR-ETT outperforms OLSR-ETX significantly in terms of packet loss, end-to-end delay, jitter, route changes, bandwidth, and overall stability, yielding much more robust, reliable, and efficient routing.