Delayed-duplicated ACK (DDA) algorithm for TCP performance enhancement to overcome packet sequence disruption in fast-handoff of Mobile IPv6

Mobile IP is proposed to support host mobility in the Internet. However, during a handoff the Mobile IP suffers from packet sequence disruption as well as packet loss. The handoff also severely affects the conventional TCP, which was designed without considering mobility. Several versions of mobile TCPs are introduced focusing on freezing the transfer during the handoff. Also, although existing fast handoff proposals can reduce handoff latency and packet loss, there remains packet sequence disruption (i.e., out-of-order delivery). We describe a new TCP, delayed-duplicated ACK (DDA) TCP, to overcome the out-of-order delivery problem in the Mobile IP networks. The TCP-DDA estimates the time duration, UTP (unstable time period), while the packet can be out-of-order. It then suppress sending duplicated ACK during the UTP so that it does not enter the retransmission procedure. The proposed scheme maintains end-to-end TCP semantics and does not require any new entity between the sender and the receiver. Only a small change is required to estimate the UTP value at the TCP receiver. Simulation result shows that the proposed scheme can yield better performance than the conventional TCP.