Performance of TCP can be severely degraded in Mobile IP-based wireless networks where packet losses not related to network congestion occur frequently during inter-subnetwork handoffs by user mobility. To solve such a problem in the networks using Mobile IP, the packet buffering method at a base station recovers those packets dropped during handoff by forwarding the buffered packets at the old base station to the mobile users. But, when the mobile user moves to a congested base station in a new foreign subnetwork, those buffered packets forwarded by the old base station are dropped and TCP transmission performance of a mobile user degrades severely. In this paper, we propose a PFC (Packet Forwarding Controller) required at a base station to increase TCP throughput in Mobile IP-based networks. The PFC at the old base station forwards or discards the buffered packets during handoffs according to the current status of RED (Random Early Detection) buffer at the congested FA (Foreign Agent) router. Simulation results show that PFC increases throughputs of TCP flows and link utilization.