WLANs (Wireless Local Area Networks) have become ubiquitous in our everyday life, and are mostly based on IEEE 802.11 standards. In this paper, we consider the performance evaluation of an arbitrary-topology unsaturated network based on the IEEE 802.11 DCF. We present a conflict graph- based modeling approach to discover the attainable throughput of each node. Our model consists of a single Markov chain which aims at describing, at a high-level of abstraction, the current state of the entire wireless network. Owing to its low complexity, our approach is simple to implement, can cope with medium sized networks, and its execution speed is fast. We validate its accuracy against a discrete-event simulator. Results show that our approach is typically accurate, with associated relative errors generally less than 15%, and that it captures complex phenomena such as node starvation. We investigate two potential applications of our proposed approach in which, starting with a given network, we improve its performance in terms of overall throughput or fairness by throttling the throughput demand of a node, or by turning a node off altogether.