The IEEE802.11 standard for wireless local area networks is based on the CSMA/CA protocol for supporting asynchronous data transfers. CSMA/CA uses an acknowledgment mechanism for verifying successful transmissions and optionally, a handshaking mechanism for decreasing collisions overhead. In both cases, an exponential backoff mechanism is used. This work investigates the theoretical performance of both mechanisms in terms of throughput and delay under traffic conditions that correspond to the maximum load that the network can support in stable conditions. We present extensive numerical results in order to highlight the effect of the backoff mechanism parameters on network performance for both mechanisms.