The purpose of this paper is to analyze the so-called backoff technique of the IEEE 802.11 protocol with buffers. In contrast to existing models, packets arriving when a station (or node) is in backoff state are not discarded, but are stored in a buffer of infinite capacity. As in previous studies, the key point of our analysis hinges on the assumption that the time on the channel is viewed as a random succession of transmission slots (whose duration corresponds to the length of a packet) and mini-slots during which the backoff of the station is decremented. These events occur independently, with given probabilities and there is a Poisson external process. The state of a node is represented by a three-dimensional Markov chain in discrete-time, formed by the triple (backoff counter, number of packets at the station and the transmission attempt number). The stability (ergodicity) conditions are obtained for an arbitrary station and interpreted in terms of maximum throughput. Several approximations related to these models are also discussed.