The Research And Implementation On The Fault Detection And Recovery Of BFD-based MPLS Tunnel

With the expansion of network size and the diversification of network applications, the network is required to detect the fault and recover from it quickly. However, traditional IP network can not meet the requirements of some real-time services like multi-media which need a fast recovery. Being the core technology of the next-generation backbone network, the most important characteristics of Multi-protocol label switching (MPLS) are the faster detection, faster recovery and higher reliability when the network fault occurs. The MPLS label switching technology doesn't only provide more effective QoS guarantee and traffic engineering, but also has stronger survivability than the traditional IP network.In order to reduce the influence on current business when some network equipment is out of order and improve the network's reliability, the network equipment needs to detect the network communication fault among itself and its adjacent network equipments as soon as possible, and then takes corresponding measures to ensure that the current businesses continue to run normally. Bidirectional Forwarding Detection (BFD) protocol provides a simple, lightweight and abstract method for rapid fault detection on network link and forwarding. Compared with the traditional fault detection of "Hello" mechanism, BFD fault detection mechanism has many unique advantages such as Low-cost and short cycle. Because of its simplicity and unitary method of fault detection, BFD can focus on the forwarding plane, which makes the fault detection capacity of BFD up to the millisecond level, and thus becomes the best solution of rapid fault detection.In order to improve network fault's detectability and restorability, this thesis researches on the fault detection and recovery of BFD-based MPLS tunnel to increase the speed of network fault detection and recovery. The thesis includes two aspects. One is the fault detection of MPLS tunnel based on BFD technology, and the other is fault recovery technology based on protected switching mechanism.In order to make up for the defects in BFD fault detection mechanism, the thesis implements a project called the MPLS tunnel fault detection by combining the BFD and the MPLS LSP-Ping together. MPLS LSP-Ping can be used to detect the consistency between the data plane and the control plane, and BFD detection mechanism is used to detect the fault of the data plane on the MPLS label switched path, so that the overall capacity of the network fault detection is improved.For the network fault recovery, the thesis focuses on the project of fault recovery scheme based on the protected switching mechanism. On one hand, by the way of establishing a backup tunnel for the protected tunnel in advance to increase the speed of network fault recovery, it doesn't only shorten the recovery time of network fault but also reduce the loss rate of network packets. On the other hand, the problem of network packets disorder in Haskin scheme has been solved efficiently through embedding a disorder control label in the inner layer of MPLS packets as a symbol of network packets sequence.According to the methods mentioned above, a system solution for fault detection and recovery of BFD-based MPLS tunnel has been formed. It triggers the mechanism of protected switching of MPLS tunnel quickly via the result of fault detection based on BFD, and then increases the speed of network fault detection and recovery. After tested by various ways of networking, this program achieves satisfying results, not only increasing the detection rate and the recovery rate of network fault largely, but also reducing the network packets'loss and disorder greatly, which meets the requirements of the high real-time services like multi-media.