An Enhanced TCP Scheme for Distinguishing Non-congestion Losses from Packet Reordering over Wireless Mesh Networks

Wireless Mesh Network (WMN) is a communication networks, which aims to provide ubiquitous high bandwidth access for a large number of users. Transmission Control Protocol (TCP) is the most popular connection oriented transport layer protocol used in the current internet. However, when TCP operates in WMNs, the throughput of TCP degrades drastically due to its inability to distinguish non-congestion events such as non-congestion losses and packet reordering from network congestion. In addition, when non-congestion loss and packet reordering are co-existed the number of unnecessary retransmission increases and will have adverse effects on TCP and its congestion control mechanism which deteriorate the poor performance of TCP. Several loss differentiation algorithms have been proposed for distinguishing the non-congestion events from network congestion. However, the existing schemes have no mechanism to differentiate non-congestion losses from packet reordering. In this paper, we designed a new TCP scheme called TCP NJ-Plus, which is capable of distinguishing non-congestion losses from packet reordering by gathering information from the current status of the network at the time of receiving three duplicate acknowledgments and react accordingly. The simulation results using Qualnet 4.5 confirm that, TCP NJ-Plus achieves more than 20% throughput improvement over existing TCP schemes when the network co-existed with congestion, non-congestion loss and packet reordering.