TCP Fairness in Multipath Transport Protocols
Ronald Tse · 2006
Abstract — Multipath transfers are a promising technique for enhancing the reliability of Internet connections, making better use of multihoming, and using spare network capacity. However, naive designs and implementations of multipath transfer protocols risk substantial unfairness to well-behaved TCP flows. In this paper, we propose two definitions of multipath TCP-fairness, and we show that multipath transport can compete fairly with traditional TCP flows. We describe three approaches for achieving fair multipath TCP transfers. In each scheme, congestion control is performed independently on each of many subflows over which data are striped. We examine each scheme’s ability to adhere to our proposed definitions of multipath TCP fairness, and evaluate two promising, novel approaches: a priority-based scheme that rapidly backs off on most congested paths, and a bilevel scheme that performs an additional level of congestion control on top of its many subflows. Our evaluation shows that both approaches meet our definition of multipath fairness while readily consuming spare bandwidth. Comparisons to previous multipath approaches demonstrate scenarios in which they exhibit unfairness to traditional TCP flows. I.