MPTCP Is Not Pareto-Optimal: Performance Issues and a Possible Solution
MPTCP Is Not Pareto-Optimal: Performance Issues and a Possible Solution
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DOI：
10.1109/tnet.2013.2274462
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发表时间：
2013-10-01
影响因子：
3.7
通讯作者：
Le Boudec, Jean-Yves
中科院分区：
文献类型：
--
作者：
Khalili, Ramin;Gast, Nicolas;Le Boudec, Jean-Yves
最近提出了多路径TCP (MPTCP)，作为透明地支持到应用层的多个连接的机制。IETF正在对此进行讨论。然而，我们证明了当前的MPTCP存在两个问题：P1)将一些TCP用户升级到MPTCP会降低其他用户的吞吐量，而对升级后的用户没有任何好处，这是一种非帕累托最优的症状；P2) MPTCP用户可能对TCP用户过于咄咄逼人。我们将这些问题归因于MPTCP的链接增加算法（LIA），更具体地说，是由于在拥挤路径上传输的流量过多。LIA的设计迫使在最优资源池和响应性之间进行权衡。我们重新审视这个问题，并说明同时提供这两个属性是可能的。我们在Linux内核中实现了结果算法，称为机会关联增加算法（OLIA），并通过模拟和理论分析在我们的测试平台上研究了它的性能。我们证明了OLIA是pareto最优的，并且满足MPTCP的设计目标。因此可以避免P1和P2的问题。我们的测量和模拟表明，具有OLIA的MPTCP与具有LIA的MPTCP一样具有响应性和非flappy，并且它解决了问题P1和P2。
Multipath TCP (MPTCP) has been proposed recently as a mechanism for transparently supporting multiple connections to the application layer. It is under discussion at the IETF. We nevertheless demonstrate that the current MPTCP suffers from two problems: P1) Upgrading some TCP users to MPTCP can reduce the throughput of others without any benefit to the upgraded users, which is a symptom of not being Pareto-optimal; and P2) MPTCP users could be excessively aggressive toward TCP users. We attribute these problems to the linked-increases algorithm (LIA) of MPTCP and, more specifically, to an excessive amount of traffic transmitted over congested paths. The design of LIA forces a tradeoff between optimal resource pooling and responsiveness. We revisit the problem and show that it is possible to provide these two properties simultaneously. We implement the resulting algorithm, called the opportunistic linked-increases algorithm (OLIA), in the Linux kernel, and we study its performance over our testbed by simulations and by theoretical analysis. We prove that OLIA is Pareto-optimal and satisfies the design goals of MPTCP. Hence, it can avoid the problems P1 and P2. Our measurements and simulations indicate that MPTCP with OLIA is as responsive and nonflappy as MPTCP with LIA and that it solves problems P1 and P2.