Ad hoc networks have attracted a lot of attention due to their decentralized architecture and potential mobility. The volatile links that are inherent to these networks have generated a need for a cross-layering interface at the medium access layer (MAC) to provide reliable link metrics. Such metrics can be used for local route and quality of service decisions, as well as being disseminated to participating hosts. This thesis presents a wireless device driver that incorporates implementations of both an active probing and a passive listening method for residual bandwidth estimation. The estimates are calculated per peer for the shared channel. We also show how the estimates can be used by a network layer traffic shaper for class based traffic differentiation, thus encompassing cross-layer architecture issues.