Suitable For Hybrid Wired / Wireless Network Transmission Control Protocol

The transmission Control Protocol (TCP) provides end-to-end, reliable, congestion controlled connections over the Internet. It has been the dominant transport mechanism for reliable data transfer over the Internet. However, Reliable transport protocol, TCP, that has been traditionally used for wired networks do not perform as well on wireless networks. This is because TCP assumes that packet loss and unusual delays are mainly caused by congestion. TCP is thus tuned to adapt to such congestion losses by slowing down the amount of data it transmit in order to reduce the load and congestion on the network. In wireless networks packet loss is often caused due to other factors besides congestion. Wireless channels often suffer from high bit error rates and intermittent connectivity due to handoffs. TCP has no mechanism to differentiate these losses from congestion, and therefore unfortunately treats all losses as congestion and invokes its congestion control measures by reducing its transmission window and in effect having the throughput of the connection. This results in an unnecessary reduction in end-to-end throughput.In this paper we propose WNR-TCP, a new improvement of TCP NewReno for wired/wireless networks. It can differentiate congestion loss from wireless link loss and invoke appropriate error recovery schemes for different cause. This method has three contributions: congestion is determined by calculating the relative forward delay that one data packet experiences as it traverses the wired/wireless networks; WNR-TCP monitors the packet's delay developing at the source and thus determine whether congestion is increasing in the network; it can then identify losses as either congestive or random; when the result shows that packet loss is due to congestion, the sender invoke the traditional congestion control method, otherwise the packet loss is due to link loss, the sender just need to retransmit the packet without decreasing the send rate.We have simulated WNR-TCP under ns-2 and implemented the prototype of WNR-TCP under Linux in order to testify its validity. The performance evaluation...