Cascading Failure Analysis And Research On Detecting And Controlling Technologies In Internet

With the rapid development of Internet, especially the amount of users and applications growing at a tremendous rate in recent years, network topology is becoming larger and more complicated and traffic is growing exponentially. Although the throughput of routing equipment is constantly increasing, it lags behind the increasing rate of user's bandwidth demand. Then this makes certain nodes work in a state of high load. If such nodes are attacked, such as virus, it will lead to be overloadable and incapable of working, forcing data packets to reroute, thereby causing other routers to overload successively, and resulting in the cascading failures. Once the large-scale cascading failures take place, they often engender the destructivity and influence powerfully. Therefore, it is necessary to systematically research on the occurred mechanisms and control technologies of cascading failures of Internet.Currently, the varieties of scientific knowledge and research about various quantitative and qualitative features of the complex network have become an extremely important challenging topic in networkable era for scientific research. Recent studies have revealed that the failure of one or a few nodes or edges (this may be a random failure, also the result of deliberate attacks) can cause other nodes to fail through the coupled relations between nodes, then it would be a domino effect and lead to the collapse of a considerable number of nodes or even the entire network. Internet is the largest artificial complex network and traditionally it's mainly focusing most attention on preventing cascading failures, such as the capacity of the routers located in the trunk of Internet often being larger than normal, usually there being redundant links between core nodes, etc. However, the large-scale cascading failures still occur at times and people lack effective response mechanism to the cascading failures, it is mainly owing to the lack of the research on control technology and the understanding of cascading failures of Internet.Based on summarizing series of important research works of the complex network's cascading failures, analyzing the characteristics of Internet topology and traffic, in view of the characteristics of heterogeneous distribution of loads and learning from the worm early detection as well as the control technology of forest fire, this paper presents a"two-stage approach"control method for restraining the cascading failures of Internet by closing some nodes or links initiatively. Through the analysis of the propagational characteristics of the cascading failures, this method divides it into two phases: the slow start and the rapid propagation. Through effective control technologies we can detect the cascading failures at the slow-start phase, and then perform the fast response mechanism and timely take measures to prevent cascading failures into rapid-propagation phase so as to cause massive outbreak of Internet failures and then result in collapse of the entire network. Therefore, there are two key points: the early detection of cascading failures together with the effective and fast response mechanism for this approach.The goal of the early detection phase is as early as possible to detect cascading failures occurred. A threshold of "target" is generally defined in traditional methods, such as the number of computers infected by worm virus or nodes and links of their load exceeding the capacity, and then the shortcoming of the methodology is high false alarm rate. Combining the ideas of rate detection in the worm early detection area, this paper proposes the detection thinking of "detecting the trend not the threshold" and filters the number of "target" in unit time with some rules. One of characteristics of Internet communication is traffic burst so as to make the loads of some nodes occasionally exceed their capacity, however, that does not necessarily lead to the occurrence of cascading failures. Generally speaking, a communication protocol with the function of flow regulation would make the nodes carrying minor overload restore to the baseline without resulting in massive nodes overloaded, thus triggering cascading failures. It was thought that the phenomenon is noise and cascading failures occur only when the number of overloadable nodes and links exists a stable plus trend.The aim of effective and fast response mechanism is to slow and prevent cascading failures from the large-scale propagation. Traditional methods only just tolerate a small degree of traffic burst not completely avoid cascading failures, furthermore needing additional investment result in some waste of resources. The ignition-help method which is widely used to control the forest fire was absorbed in this paper. According to the loads of the various nodes and links in Internet when detecting the occurrence of cascading failures at the slow-start phase, premising not significantly reducing the efficiency of network, the method initiatively closes some of certain "flow generator" nodes or links with high load, mainly because from the perspective of traffic engineering, each node in Internet has two functions. They act as transmitters, which distribute load, and generators, which create load. The former than the latter is called "flow generator" node, which is the main traffic producer and has little impact on the connectivity of entire network; otherwise known as "flow transmitter" node which is the main flow distributor and constitutes the core of entire network. The method can reduce the load of the entire network by closing some of certain "flow generator" nodes, which can reach a balanceable distribution of load. Because the links with large load often connect with the "flow generator" nodes and "flow transmitter" nodes, the method closes such links that can effectively reduce the load of "flow transmitter" nodes and avoid their failures as a result of overload and leading to the collapse of the entire network for broken.The experiments show that the two-stage approach proposed in this paper is capable of not only effectively and timely restraining the large-scale propagation of cascading failures, but not significantly reducing the efficiency of the entire network, ensuring the majority of users can work normally.