This paper presents a comparative analysis on the signaling cost functions of Mobile IP (MIP) with different paging protocols and schemes and investigates constructing optimal paging areas using discrete system model as a mobility model. In wireless mobile Internet, mobile users often visit foreign networks that might be far away from their home networks and the occurrences of their inter-domain movement are relatively rare. In this scenario, our analytical results show that paging, particularly individual paging, can significantly improve the total signaling cost of MIP. We show that Domain paging can bring about considerable cost saving compared to FA (Foreign Agent) paging. Our results also demonstrate the significant advantages of Individual paging over Aggregate paging. The results show that specifying the optimal PA size is critical in saving signaling cost of MIP with paging support.