Hash-based internet traffic distribution and tcp performance analysis
Francis L. Merat, Ju-Yeon Jo · 2003
IP packet transmission over multiple parallel links is in extensive use in today's Internet and its use is growing due to its scalability, reliability and cost-effectiveness. To maximize the efficiency of parallel links load balancing is necessary among the links; however, this may cause a problem with packet reordering. Since packet reordering impairs the performance of TCP or other application, it is important to reduce the amount of reordering. Hashing offers a simple solution to maintaining the packet order by sending a flow over a unique link; however, static hashing and conventional dynamic hashing do not achieve load balancing at adequate levels. We have enhanced the dynamic hashing algorithm to use flow volume information to reassign only appropriate flows. This new method, called dynamic hashing with flow volume (DHFV), eliminates unnecessary reassignments of small flows. It achieves load balancing very quickly without load fluctuation by accurately predicting the amount of transferred load between the links. We provide the general framework of DHFV and address the challenges in implementing DHFV. We analyze the TCP performance under packet loss and packet reordering to show that packet reordering has less impact on TCP performance. Simulation results show that DHFV reduces the packet loss by 97% compared to static hashing and reduces the number of flow reassignments by 98% compared to dynamic hashing. When compared with a single link, Multilink with DHFV allows the receiving host to receive approximately 98% of the TCP traffic with only 0.4% additional traffic generated. Static hashing allows approximately 97% of the TCP traffic to be received with 5.5% additional traffic as compared to a single link. Dynamic hashing does not perform well either and allows only 89% of the TCP traffic to be received with 6.9% additional traffic. DHFV performs better than either static or dynamic hashing with performance approaching that of a comparable single link.