Control traffic balancing in software defined networks
Control traffic balancing in software defined networks
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DOI：
10.1016/j.comnet.2015.08.004
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发表时间：
2016-09-04
影响因子：
5.6
通讯作者：
Luo, Min
中科院分区：
文献类型：
--
作者：
Lin, Shih-Chun;Wang, Pu;Luo, Min
为了保证软件定义网络（sdn）中的在线和自适应流量工程，控制消息，例如每个新流的第一个数据包和网络流量统计，应该以快速和健壮的方式从软件定义交换机转发到控制器。由于sdn中需要许多信令事件和控制平面操作，因此它们很容易产生大量必须与数据流量一起处理的控制流量。然而，带内控制信道的使用对控制业务的及时可靠传输提出了很大的挑战，而带外控制通常成本过高。为了解决这一问题，本文首先将控制流量均衡问题表述为一个非线性优化框架，其目标是找到每个交换机的最优控制流量转发路径，使整个网络的平均控制流量延迟最小化。这个问题在sdn中非常关键，因为由Openflow交换机发起的控制流量的及时交付直接影响路由策略的有效性。具体地说，给出了公式化的非线性问题和解集的基本数学结构，并据此提出了一种有效的算法，称为多项式时间逼近算法（PTAA），该算法利用乘法器的交替方向法（ADMM）快速收敛到近最优解。此外，研究了带内模式下控制器的最优配置问题，该问题旨在通过最小化控制消息延迟来找到控制器可以配置的最优开关位置。除了定量或启发式的结果外，目前还没有广泛的研究，但从交通统计的角度出发，提出了一种简单有效的算法来保证最优布局。仿真结果表明，所提出的PTAA能显著降低时延，极大地方便了大规模sdn中控制器的流量工程。(C) 2015 Elsevier B.V.版权所有
To promise on-line and adaptive traffic engineering in software defined networks (SDNs), the control messages, e.g., the first packet of every new flow and network traffic statistics, should be forwarded from software defined switches to the controller(s) in a fast and robust manner. As many signaling events and control plane operations are required in SDNs, they could easily generate a significant amount of control traffic that must be addressed together with the data traffic. However, the usage of in-band control channel imposes a great challenge into timely and reliable transmissions of control traffic, while out-band control is usually cost-prohibitive. To counter this, in this paper, the control traffic balancing problem is first formulated as a nonlinear optimization framework with an objective to find the optimal control traffic forwarding paths for each switch in such a way the average control traffic delay in the whole network is minimized. This problem is extremely critical in SDNs because the timely delivery of control traffic initiated by Openflow switches directly impacts the effectiveness of the routing strategies. Specifically, the fundamental mathematical structures of the formulated nonlinear problem and solution set are provided and accordingly, an efficient algorithm, called polynomial-time approximation algorithm (PTAA), is proposed to yield the fast convergence to a near optimal solution by employing the alternating direction method of multipliers (ADMM). Furthermore, the optimal controller placement problem in in-band mode is examined, which aims to find the optimal switch location where the controller can be collocated by minimizing the control message delay. While it is not widely researched except quantitative or heuristic results, a simple and efficient algorithm is proposed to guarantee the optimum placement with regards of traffic statistics. Simulation results confirm that the proposed PTAA achieves considerable delay reduction, greatly facilitating controller's traffic engineering in large-scale SDNs. (C) 2015 Elsevier B.V. All rights reserved.