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University: Case Western Reserve University
Professor: Prof. Frank L. Merat
Department: Department of Electrical Engineering and Computer Science

Research Topic: Load balancing schemes for multilink and their impact on TCP performance

Sending IP packets 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, but it may cause the problem of packet reordering. Since packet reordering impairs TCP performance, it is important to reduce the amount of reordering as well as packet loss. While resequencing the out-of-order packets is considered expensive, hashing offers a simpler solution by sending a flow over a unique link. However static hashing does not guarantee an even distribution of the traffic amount among the links, which could lead to packet loss under a heavy load. Dynamic hashing offers some degree of load balancing but suffers from load fluctuations and excessive packet reordering.

To overcome these shortcomings, we have enhanced the dynamic hashing algorithm to utilize the flow volume information. This new method, called dynamic hashing with flow volume (DHFV), eliminates unnecessary flow reassignments of small flows and achieves load balancing very quickly without load fluctuation by accurately predicting the amount of transfered load between the links.

To observe the behavior of TCP under various load-balancing methods, we are using OPNET Modeler to create a multilink environment and to generate massive TCP flows. We are studying the effect of packet loss and reordering for different versions of TCP. Current simulation result shows that DHFV is much more TCP-friendly than static or dynamic hashing with very little packet loss.