A Improvement Of The CETEN Scheme Based On Probability Estimate

The wireless link has become an important constituent of network nowadays. Nevertheless, while providing the brand-new experiences, the wireless network actually has the flaws, for example, the low bandwidth, high error rate and so on. The TCP is a most wide protocol and be used most wide at present. It has been applied to broad domain. The TCP consider the packet loss caused by the congestion, in the wired network TCP can avoid congestion very effectively. But when TCP is applied to the wireless network, there exist some certain questions. TCP is unable to distinguish the reasons of the package loss. It only considers the package caused by congestion, but actually this packer is caused by error, so the TCP use the unnecessary mechanisms to avoid the congestion. By do this, the performance will decline. In the wireless network, CETEN(Cumulative Explicit Transport Error Notification) can be used to enhance the performance of the TCP.For reducing the dependence on router, this paper in view of the CETEN to make the improvement. In receiver side, the OTTE algorithm used to estimate drop rate of the packets which caused by error. OTTE uses the holes which in the TCP receive stack, and use the timestamp to judge the cause of formation of the holes. Thus the quantities of loss packages created by mistake and by congestion will be estimated, and the loss rate by mistake will be computed too. At last, transmit the information to the sender by the explicit feedback mechanism, and adjust the congestion control algorithm of TCP. The biggest advantages of OTTE is need the support by the router, is more accord with end-to-end design. Compare with the CETEN which can accurate estimate the error rate of the link, the OTTE can improve the performance about 10%.The primary negative factor which affects the CETEN's performance is the packet reordering, it make LEAST algorithm estimated value inaccuracy. Actually, the packet reordering is inevitable, the only way to reduce its adverse effect is reduce re-transmit data packet. This paper use bubble sorting in the receiver side to estimated reordering probability, and notice the sender by explicit feedback. The sender alters the dupthresh value, achieves the goal of reduced nonessential re-transmitted packets. This scheme can gains 41%-57% increment of the throughput, and compare to CETEN, the RE-CETEN also obtained the higher friendliness.Packet Reordering also is the primary factor which is limiting OTTE to apply in the complex network environment. The Reordering make the value of OTTE to have deviation, the performance not as good as CETEN. This paper applies the ordinal packets which are the attached result of RE-CETEN, as input of OTTE, achieve the goal to shields the influence of reorder, and make OTTE to adapt to the more complex network. Simultaneously, uses the timestamp of OTTE also enhance the efficiency of RE-CETEN in a certain extent.