Shiduan Cheng

On reliability-optimized controller placement for Software-Defined Networks

By decoupling control plane and data plane, Software-Defined Networking (SDN) approach simplifies network management and speeds up network innovations. These benefits have led not only to prototypes, but also real SDN deployments. For wide-area SDN deployments, multiple controllers are often required, and the placement of these controllers becomes a particularly important task in the SDN context. This paper studies the problem of placing controllers in SDNs, so as to maximize the reliability of SDN control networks. We present a novel metric, called expected percentage of control path loss, to characterize the reliability of SDN control networks. We formulate the reliability-aware control placement problem, prove its NP-hardness, and examine several placement algorithms that can solve this problem. Through extensive simulations using real topologies, we show how the number of controllers and their placement influence the reliability of SDN control networks. Besides, we also found that, through strategic controller placement, the reliability of SDN control networks can be significantly improved without introducing unacceptable switch-to-controller latencies.

On the placement of controllers in software-defined networks

Abstract The software-defined network (SDN) approach assumes a logically centralized control plane, which is physically decoupled from the data plane. Since this approach simplifies network management and speeds up network innovations, these benefits have led not just to production-intent prototypes, but real SDN deployments. For wide-area SDN deployments, multiple controllers are often required, and the placement of these controllers influences every aspect of an SDN. Since optimizing every metric is generally an non-deterministic polynomial (NP)-hard problem, it is of great importance to find an efficient controller placement algorithm. In this paper, we develop several placement algorithms to make informed placement decisions, which can be used to maximize the reliability of SDN, since network failures could easily cause disconnections between the control and forwarding planes. These algorithms are evaluated using real topologies. Simulation results show that the controller placement strategies are crucial to SDN performance, and a greedy algorithm provides placement solutions that are close to optimal.

QoE-Driven Cross-Layer Optimization for Wireless Dynamic Adaptive Streaming of Scalable Videos Over HTTP

Recently, Dynamic Adaptive Streaming over HTTP (DASH) has attracted significant attention. In this paper, we consider DASH-based transmission of scalable videos in wireless broadband access networks (e.g., long-term evolution and WiMAX), and propose three methods to enhance the quality of experience of wireless DASH users. First, we design an improved mapping scheme from scalable video coding layers to DASH layers that can provide the desired bitrates, enhance the video end-to-end throughput, and reduce the HTTP communication overhead. Second, we develop a DASH-friendly scheduling and resource allocation algorithm by integrating the DASH-based media delivery and the radio-level adaptation via a cross-layer approach. It utilizes the characteristics of video content and scalable video coding, and greatly reduces the possibility of video playback interruption by considering the client buffer status. The optimization problem is formulated as a mixed binary integer programming problem, and is solved by a subgradient method. Finally, a DASH proxy-based bitrate stabilization algorithm is proposed to improve the video playback smoothness that can achieve the desired tradeoff between playback quality and stability. Simulations with the Qualnet tool demonstrate that our schemes achieve better performances than other methods in the literature.

Fault management for Internet Services: Modeling and Algorithms

A modeling approach is proposed in this paper to build the bipartite fault propagation model (FPM) for Internet services. The FPM is layered as Internet services involve multiple layers. Two fault localization algorithms, MCA (Max-Covering Algorithm) and MCA+, are designed for the bipartite FPM. MCA+ is an extension of MCA, taking lost and spurious symptoms into account. Simulation results show that MCA+ achieves high detection rate, low false positive rate and has polynomial computational complexity even in the presence of lost and spurious symptoms.

Scheduling and resource allocation for wireless dynamic adaptive streaming of scalable videos over HTTP

Recently dynamic adaptive streaming over HTTP (DASH) has gained significant attentions. In this paper, we study DASH-based transmission of scalable videos in wireless broadband access networks (e.g. LTE, WiMAX), and propose a DASH-friendly scheduling and resource allocation scheme (DFSRA) to enhance the Quality-of-Experience (QoE) of wireless DASH users. By integrating DASH-based media delivery and radio-level adaptation in a cross-layer manner, the scheme can determine the optimal wireless resource allocation. A gradient-based algorithm is proposed to solve the optimization problem, which has the following advantages over traditional algorithms: (1) The characteristics of video content and scalable video coding are utilized. (2) The client buffer status is considered to reduce video playback interruption and buffer overflow. Simulations with the Qualnet tool demonstrate that our scheme achieves better performance than existing methods in the literature.

Energy-performance tradeoffs in IaaS cloud with virtual machine scheduling

In the cloud data centers, how to map virtual machines (VMs) on physical machines (PMs) to reduce the energy consumption is becoming one of the major issues, and the existing VM scheduling schemes are mostly to reduce energy consumption by optimizing the utilization of physical servers or network elements. However, the aggressive consolidation of these resources may lead to network performance degradation. In view of this, this paper proposes a two-stage VM scheduling scheme: (1) We propose a static VM placement scheme to minimize the number of activating PMs and network elements to reduce the energy consumption;(2) In the premise of minimizing the migration costs, we propose a dynamic VM migration scheme to minimize the maximum link utilization to improve the network performance. This scheme makes a tradeoff between energy efficiency and network performance. We design a new two-stage heuristic algorithm for a solution, and the simulations show that our solution achieves good results.

Virtual machine placement optimizing to improve network performance in cloud data centers

Abstract With the wide application of virtualization technology in cloud data centers, how to effectively place virtual machine (VM) is becoming a major issue for cloud providers. The existing virtual machine placement (VMP) solutions are mainly to optimize server resources. However, they pay little consideration on network resources optimization, and they do not concern the impact of the network topology and the current network traffic. A multi-resource constraints VMP scheme is proposed. Firstly, the authors attempt to reduce the total communication traffic in the data center network, which is abstracted as a quadratic assignment problem; and then aim at optimizing network maximum link utilization (MLU). On the condition of slight variation of the total traffic, minimizing MLU can balance network traffic distribution and reduce network congestion hotspots, a classic combinatorial optimization problem as well as NP-hard problem. Ant colony optimization and 2-opt local search are combined to solve the problem. Simulation shows that MLU is decreased by 20%, and the number of hot links is decreased by 37%.

Control traffic protection in software-defined networks

Software Defined Networking (SDN) is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnections between switches and their controllers could result in substantial packet loss and performance degradation. To achieve resilient control traffic forwarding, this paper investigates the protection of control traffic in SDNs with multiple controllers. We propose a control traffic protection scheme that combines both local rerouting and constrained reverse forwarding protections. This scheme enables switches to locally react to failures and redirect the control traffic to controllers by using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protection control network, where as much control traffic as possible can benefit from the proposed protection scheme. We formulate the protection control network problem and develop an algorithm to solve it. Simulation results on real topologies show that our approach significantly improves the resilience of control traffic.

A cloud-assisted DASH-based Scalable Interactive Multiview Video Streaming framework

Interactive multiview video streaming (IMVS) allows viewers to periodically switch viewpoint. Its user experience can be further enhanced by creating virtual views from neighboring coded views using view synthesis techniques. Dynamic adaptive streaming over HTTP (DASH) is a new standard that can adjust the quality of video streaming according to the network condition. In this paper, we propose an improved DASH-based IMVS scheme over wireless networks. The main contributions are twofold. First, our scheme allows virtual views to be generated at either the cloud-based server or the client, and can adaptively select the optimal approach based on the network condition and the cost of the cloud. Second, scalable video coding is used in our system. Simulations with the NS3 tool demonstrate the advantage of our proposed scheme over the existing approach with client-based view synthesis and single-layer video coding.

On the feasibility and efficacy of control traffic protection in software-defined networks

Software Defined Networking (SDN) is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnections between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to failures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles protectability and performance (e.g., switch-to-control latency). Through extensive simulations based on real topologies, we show that our approach significantly improves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.摘要创新点1、提出了多控制器软件定义网络中, 同时使用本地重路由保护和受限的逆向路径转发保护的使用方法.2、对可保护控制网络问题进行建模, 并证明了计算一个允许一定逆向路径转发跳数的可保护控制网络是 NP-难问题, 并分析了保证可保护性的充分条件.3、提出了一种新的基于模拟退火的可保护控制网络计算算法. 该算法不但考虑了多控制器环境中控制流保护方案的应用, 而且在优化可保护性的同时最小化了对网络传播延时的影响.4、进行了基于真实网络拓扑的详尽实验, 对所提出的控制流保护机制及算法加以验证.