This paper reviews 802.16 2001's MAC layer QoS metric. It explains the importance of QoS and its parameter set; defines types of services supported by this standard; explores the main entity of the MAC layer used for transportation that is service flow and how the QoS metric is associated with it, as well as the relationship of service class and service flow. It further explains the authorization model and two phase activation. In the end it explains dynamic service flow and dynamic service messages in detail ...