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구글 TensorFlow 소개

Software defined networking (SDN) decouples the control plane from the data plane of forwarding devices. This separation provides several benefits, including the simplification of network management and control. However, due to a variety of reasons, such as budget constraints and fear of downtime, many organizations are reluctant to fully deploy SDN. Partially deploying SDN through the placement of a limited number of SDN devices among legacy (traditional) network devices, forms a so-called hybrid SDN network. While hybrid SDN networks provide many of the benefits of SDN and have a wide range of applications, they also pose several challenges. These challenges have recently been addressed in a growing body of literature on hybrid SDN network structures and protocols. This paper presents a comprehensive up-to-date survey of the research and development in the field of hybrid SDN networks. We have organized the survey into five main categories, namely hybrid SDN network deployment strategies, controllers for hybrid SDN networks, protocols for hybrid SDN network management, traffic engineering mechanisms for hybrid SDN networks, as well as testing, verification, and security mechanisms for hybrid SDN networks. We thoroughly survey the existing hybrid SDN network studies according to this taxonomy and identify gaps and limitations in the existing body of research. Based on the outcomes of the existing research studies as well as the identified gaps and limitations, we derive guidelines for future research on hybrid SDN networks.

Hybrid SDN Networks: A Survey of Existing Approaches

It is widely acknowledged that the development of traditional terrestrial communication technologies cannot provide all users with fair and high quality services due to scarce network resources and limited coverage areas. To complement the terrestrial connection, especially for users in rural, disaster-stricken, or other difficult-to-serve areas, satellites, UAVs, and balloons have been utilized to relay communication signals. On this basis, SAGINs have been proposed to improve the users' QoE. However, compared with existing networks such as ad hoc networks and cellular networks, SAGINs are much more complex due to the various characteristics of three network segments. To improve the performance of SAGINs, researchers are facing many unprecedented challenges. In this article, we propose the AI technique to optimize SAGINs, as the AI technique has shown its predominant advantages in many applications. We first analyze several main challenges of SAGINs and explain how these problems can be solved by AI. Then, we consider the satellite traffic balance as an example and propose a deep learning based method to improve traffic control performance. Simulation results evaluate that the deep learning technique can be an efficient tool to improve the performance of SAGINs.

Optimizing Space-Air-Ground Integrated Networks by Artificial Intelligence

is a network or group of networks under a common administration and with common routing policies. BGP is used to exchange routing information for the Internet and is the protocol used between Internet service providers (ISP). Customer networks, such as universities and corporations, usually employ an Interior Gateway Protocol (IGP) such as RIP or OSPF for the exchange of routing information within their networks. Customers connect to ISPs, and ISPs use BGP to exchange customer and ISP routes. When BGP is used between autonomous systems (AS), the protocol is referred to as External BGP (EBGP). If a service provider is using BGP to exchange routes within an AS, then the protocol is referred to as Interior BGP (IBGP).

Border Gateway Protocol

The detection of DDoS attacks is an important topic in the field of network security. The occurrence of software defined network (SDN) (Zhang et al., 2018) brings up some novel methods to this topic in which some deep learning algorithm is adopted to model the attack behavior based on collecting from the SDN controller. However, the existing methods such as neural network algorithm are not practical enough to be applied. In this paper, the SDN environment by mininet and floodlight (Ning et al., 2014) simulation platform is constructed, 6-tuple characteristic values of the switch flow table is extracted, and then DDoS attack model is built by combining the SVM classification algorithms. The experiments show that average accuracy rate of our method is with a small amount of flow collecting. Our work is of good value for the detection of DDoS attack in SDN.

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A DDoS Attack Detection Method Based on SVM in Software Defined Network

Satellite networks are drawing more and more attention, since they can provide various services to everywhere on the earth. Communication devices in satellites are typically powered by solar panels and battery cells, which are carefully designed to guarantee power supply and avoid deficiency. However, we find that unrestrained use of energy will cause a satellite to age quickly, because the number of recharge/discharge of battery cells is limited. Due to the extremely high cost of satellites, the development of energy-efficient satellite routing to save energy and prolong satellite lifetimes has become significantly important. In this paper, we do comprehensive studies. First, we model the power consumption of a space router, power supply by solar panels, and aging of battery cells formally. Second, we define the energy-efficient satellite routing (EESR) problem, and prove that the EESR problem is NP-hard. Then, we develop three algorithms to gradually solve the EESR problem. GreenSR-B is a baseline algorithm which computes link costs iteratively to compute a routing that minimizes the total recharge/discharge cycle number. GreenSR-A selects space routers to switch into sleep mode to improve energy conservation. GreenSR jointly considers energy efficiency and QoS requirements of path length and the maximum link utilization ratio. We evaluate our algorithms by simulations on a low earth orbit satellite network with real Internet usage traces. The results show that GreenSR can prolong the lifetime of satellite battery cells by more than 40%, with little increment in path length and a small link utilization ratio.

Towards Energy-Efficient Routing in Satellite Networks

Software-Defined Networking (SDN) enables network innovations with a centralized controller controlling the whole network through the control channel. Because the control channel delivers all network control traffic, its security and reliability are of great importance. For the first time in the literature, we propose the CrossPath attack that disrupts the SDN control channel by exploiting the shared links in paths of control traffic and data traffic. In this attack, crafted data traffic can implicitly disrupt the forwarding of control traffic in the shared links. As the data traffic does not enter the control channel, the attack is stealthy and cannot be easily perceived by the controller. In order to identify the target paths containing the shared links to attack, we develop a novel technique called adversarial path reconnaissance. Both theoretic analysis and experimental results demonstrate its feasibility and efficiency of identifying the target paths. We systematically study the impacts of the attack on various network applications in a real SDN testbed. Experiments show the attack significantly degrades the performance of existing network applications and causes serious network anomalies, e.g., routing blackhole, flow table resetting, and even network-wide DoS.

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The CrossPath Attack: Disrupting the SDN Control Channel via Shared Links.

The emerging Software-Defined Networking (SDN) is being adopted by data centers and cloud service providers to enable flexible control. Meanwhile, the current SDN design brings new vulnerabilities. In this paper, we explore a stealthy data plane based attack that uses a minimum rate of attack packet to disrupt SDN. To achieve this, we propose the LOFT attack that computes the lower bound of attack rate to overflow flow tables based on the inferred network configurations. Particularly, each attack packet always triggers or maintains consumption of one flow rule. LOFT can ensure the attack effect with various network configurations while reducing the possibility of being captured. We demonstrate its feasibility and effectiveness in a real SDN testbed consisting of commercial hardware switches. The experiment results show that LOFT can incur significant network performance degradation and potential network DoS at an attack rate of only tens of Kbps.

Disrupting SDN via the Data Plane: A Low-Rate Flow Table Overflow Attack

The Internet is generally not energy-efficient since all network devices are running all the time and only a small fraction of consumed power is actually related to traffic forwarding. Existing studies try to detour around links and nodes during traffic forwarding to save powers for energy-efficient routing. However, energy-efficient routing in traditional IP networks is not well addressed. The most challenges within an energy-efficient routing scheme in IP networks lie in safety and practicality. The scheme should ensure routing stability and loop- and congestion-free packet forwarding, while not requiring modifications in the traditional IP forwarding diagram and shortest-path routing protocols. In this paper, we propose a novel energy-efficient routing approach called safe and practical energy-efficient detour routing (SPEED) for power savings in IP networks. We provide theoretical insight into energy-efficient routing and prove that determining if energy-efficient routing exists is NP-complete. We develop a heuristic in SPEED to maximize pruned links in computing energy-efficient routings. Extensive experimental results show that SPEED significantly saves power consumptions without incurring network congestions using real network topologies and traffic matrices.

Safe and practical energy-efficient detour routing in IP networks

Recently, QUIC proposed by Google has drawn great attentions due to several attractive features which improve the page load time for Web applications. The features of QUIC lie across different protocol layers, and the benefits and the limitations introduced by each feature have not been understood sufficiently. In this paper, we focus on the transport aspect of QUIC, with the packet pacing mechanism for congestion control. We conduct an experimental study to evaluate the performance of QUIC as a general-purpose transport protocol, especially when QUIC is used concurrently with TCP, which is still the dominating transport protocol on the Internet. By doing so, we can exploit the potential of QUIC as a transport protocol in other application scenarios besides HTTP/2. It is also useful for the improvement of QUIC itself, because each object transmitted in one stream of a QUIC connection has to compete for resources with other transport protocols on the Internet. We do both testbed and real Internet experiments, on typical network environments such as 4G and WiFi. Our main findings indicate that, QUIC is less competitive than TCP in a network with little loss rate, large buffer, or large propagation delay; the 0-RTT connection establishment feature of QUIC has little advantage over TCP in practice; and the main benefit of QUIC lies in the multi-stream-based multiplexing mechanism.

Yuan Yang

Papers

Towards Energy-Efficient Routing in Satellite Networks

The CrossPath Attack: Disrupting the SDN Control Channel via Shared Links.

Disrupting SDN via the Data Plane: A Low-Rate Flow Table Overflow Attack

Safe and practical energy-efficient detour routing in IP networks

When QUIC meets TCP: An experimental study