Wireless networks bring a new market to service providers and terminal manufacturers. In fact after the success of the wired internet, wireless and mobile internet arrives with the ambition of providing new services to Internet users. However wireless networks face important challenging issues before attaining a similar or better success than the wired Internet. These issues are mainly related to the classical QoS, mobility, security problems, and the wireless specific problems such as the radio resource characteristics. In this article we are interested by the mobility problem and particularly the handover management problem. We introduce a policy based handover and we propose to combine the mobility management with the policy based architecture in order to achieve policy based handovers that are triggered not only on the signal strength basis, but also on policy constraints such as cost, resource availability or load balancing. The policy based architecture will provide the handover triggering mechanism and the decision support related to the best next cell where the mobile node will move. We also introduce mobility parameters in the Service Level Specification (SLS) that specifies the handover type, the accepted handover packet loss, and the accepted handover delay. Based on these SLS mobility parameters, the QoS service classes can be mapped to the smooth (minimum packet loss), the fast handover (minimum delay), or the seamless handover (fast and smooth).