MANET中TCP数据包的乱序问题及其解决方案

Mechanism for Packet Reordering in MANET

在MANET中,节点的移动性会导致不同的TCP数据包沿不同的路径到达接收端,进而在接收端产生大量的乱序数据包,影响TCP协议的性能。提出了一种延时响应TCP协议(TCP-D),通过延时触发拥塞控制算法来提高TCP协议在MANET中的性能。对延时响应TCP协议的吞吐量分析表明,增加延时定时器后,TCP_D协议仍能保证对标准TCP协议的友好性。仿真实验表明,TCP_D算法可以明显减少乱序数据包的数量,获得较标准TCP协议更高的网络吞吐量。而在网络结构稳定、无乱序数据包的情况下,改进协议仍具有很好的公平性和友好性。

The standard implementation of TCP experiences heavy throughput degradation when packets are reordered. This paper presented a new version of the TCP protocol, called TCPD, which improves its performance to mobile-induced reordering packets in mobile ad hoc network （MANET）. In TCP_D, the response to the receipt of duplicate acknowledgement is delayed by a short period to allow the receiver to receive the packets that travel in different path. We analyzed TCP_D to show that its steady state throughput is similar to the native implementations of TCP when packet reordering does not occur. The simulation results show that TCP_D performs consistently better than standard implementations of TCP under persistent packets reordering. In the case that packets are not reordered TCP_D maintains the same throughput as typical implementation of TCP （TCP-NewReno） and shares network resource fairly.