Military applications in tactical networks have quality of service (QoS) requirements. The purpose of this paper is to show that these requirements can be fulfilled by our QoS support mechanisms, implemented in a MANET based on the IEEE802.11b and the OLSR protocols. After a brief presentation of our solution, we describe its implementation on a MANET testbed made of 18 routers. Results of performance evaluation obtained from measurements are reported and compared with simulation's. They allow to conclude that this QoS support improves the quality perceived by the users in terms of delivery rate and granted throughput. The flooding optimization present in OLSR is also preserved. With QoS support, simulation results show that the network is able to admit more user flows than without it. The overhead of this QoS support is evaluated and extensive simulations also show that it is scalable to large networks.