Research And Implementation Of Distributed Bidirectional Forwarding Detection Protocol

In the background of the large amount of modern Internet users, large traffic traffic and high real-time requirements, the quality of service(QoS) of the network appears to be particularly important.Guarantee of QoS mainly consists of two aspects,the fault detection and fault recovery. The Bidirectional Forwarding Detection (BFD) protocol implemented in the thesis is the one that can rapidly detect the link failures so as to ensure the communication system to be recovered from the failures as quickly as possible.Link failure detection technologies include the technologies contained in the protocol such as Hello, Keepliving, SDH and so on. However, these technologies either do not have the universal implementation or cannot achieve the level of milliseconds of adjusting rate to send packets. The BFD protocol realized in this thesis is a simple, lightweight and abstract method with the ability of real-time detection of both the network link and system communication forwarding capacity.Comparing with other ptotocols, BFD is a specific protocol because it is only a liveness detection mechanism which it don't interferenced by any protocol and any media interference, while its detection cycle can be configured and can avoid duplication of different detection methods. In one word, BFD protocol is a universal, standardized, media-independent and protocol-independent protocol with the ability of rapid fault detection.On the Basis of analysis of the advantages and disadvantages of distributed and centralized implementations for BFD protocol,this thesis adopts the distributed implementation so that it does not affect other sub-modules in the control level,so as not to affect the stability of the system. This thesis analyzes and solves the key technical issues must be solved during the distributed implementations of BFD,such as the link aggregation, the cards communication, synchronization and so on. On the basis of overall design, we focus on the implementation of link aggregations which can dynamicly maintand the aggregated link. And then the distributed system architecture of BFD is designed.In the detailed design of the system, the link aggregateion architecture,link aggregation processes, hot inserting and pulling out actions and other key functional modules are designed. In the detailed design of the link aggregation, it makes the distinction whether the link aggregation information is issued to the line card and determines the location of the switch module.On this basis,the detailed implementation process of distributed BFD,such as its master card, line card modules, hot inserting and pulling out action and standby switch action,and so on are discussed.Then the typical application examples is given. Finally the feasibility and efficiency of the scheme designed in the thesis are verified through functional and performance test. The test results show that the design is accuracy and can ensure that the realization of the BFD protocol does not affect the implementation of other functional modules of the system, and the system can achieve the telecom-level of 50ms in protection switching.