The handoff schemes in mobile IP

In this paper the mobile IP and its handoff issues are introduced. Three main factors that affect mobile IP´s handoff performance, mobility detection, re-registration, interaction with higher layer protocols, are analyzed thoroughly. Some new schemes are proposed. A new option is proposed and is added into foreign agent advertisement message. The option contains the link layer identifiers of all the links managed by that foreign agent. Then mobile host can determine whether a mobile IP handoff is required or not soon after the link´s layer handoff. So the mobile IP handoff can be accelerated and unnecessary handoffs can be avoided. When mobile host is the TCP sender, it is proposed to send all the unacknowledged segments soon after the handoff, so as to prevent TCP timeout retransmission; when mobile host is the TCP receiver, it sends several TCP SACKs to trigger the senders fast retransmission of lost segments. The implementations of the new proposals are also outlined. At last, all the new schemes are simulated and the results show that through these schemes, the performances of mobile IP handoff are improved significantly.