Research On Sctp Transition Mechanism In Wireless Network

With the rapid and diversified development of communication technology, there are more and more network access methods. The decline in the cost of network equipment also means that more and more terminals can have several different types of network interface. TCP protocol as the traditional end-to-end transport layer protocol is being abandoned, because of some shortcomings, and that it does not support multi-homed features. SCTP transport layer protocol as a new one was born to transmit SS7signaling in an IP network. As it has a number of new features that TCP does not have, more and more researchers consider using SCTP instead of TCP, to carry Internet end-to-end business. In addition, in recent years, the explosive growth of mobile Internet also inspired a lot of SCTP researches for wireless networks.The transition of SCTP from transmitting signaling to host the end-to-end business, from wired IP network to mobile Internet, still has many challenges. Take failover mechanism studied in this thesis for example:the signaling transport is machine-oriented, thus lies heavily on reliability but lightly on efficiency. But the user-oriented service transmission needs to give more considerations to the efficiency. Wired network link is usually considered to be stable, and can set a primary path for the transaction when setting up the association, while mobile network’s bandwidth, lantency, lossrate are always changing. With a higher loss-rate, failover in mobile network tends to cause a "pingpong effect". Therefore, the study of SCTP failover mechanism in mobile network end-to-end traffic is of great importance.After careful analysis of the advantages and disadvantages of existing SCTP failover mechanisms, a new path status is introduced in the thesis, for the purpose of fast path switching and reducing the handover interruption time. Then a new state recovery algorithm related to outage time is introduced, in order to reduce the "ping-pong effect". A bandwidth estimation algorithm relies on heartbeat packets on an idle link is also discussed in the thesis. At last, a new SCTP failover mechanism is introduced based on the three algorithms studied.After theoretical analysis of the failover mechanism, NS2simulations are done by modifying the NS2source code on SCTP module, and writting the corresponding scene simulation script. Simulation results show that the failover mechanism can obviously improve the reliability and efficiency of SCTP in mobile network.At the end, the SCTP protocol stack of MAC OS X is rewritten and the mechanism is tested in a real network scenario. In the test, problems of the bandwidth estimation in short-range multi-hop wireless network are found, and the solution of improvement is also discussed.