Utilizing TTL to Enhance TCP Fairness

The existed work shows that TCP has serious unfairness problem in multiple congested router. To improve TCP fairness, some queue management schemes, such as FRED, Balanced RED, have been developed to solve this problem, but most of them require to maintain per-flow state in routers. In our previous work, we have designed a two-category classifier for Active Queue Management (AQM) to enhance TCP fairness. Although it can achieve better TCP fairness in multiple congested router, it requires some modification to TCP header. Because it is incompatible for the standard TCP, it lacks of feasibility. In this paper, we will utilize TTL field in IP header to improve TCP fairness. A three-dimensional two-category classifier is designed by extending our previous work, and a based-hops fairness enhancement algorithm (BHFE) for AQM is developed. Simulation results show that it is not only effective to enhance TCP fairness in multiple congested router but also very well to keep queue length stable and small. Moreover, a very important advantage of BHFE is that it does not requires per-flow state in router and any modifications to the standard TCP/IP.