Study On Topology Automatic Discovery In Computer Network

With the rapid development of computer network technology, every organizations depends on computer network so much that network management has become more and more vital. Therefore, it leads to a higher request to network management system. In the network management system, network topology information is the foundation of other functions. Only when the structure of network topology is mastered, can correct and effective administration operation be implemented. At present, how to discover network topology fast, efficiently and accurately is a major concern in network management field.In the field of computer network, topology is a reflection of the distribution of network devices and connections among them. Topology in administrative domain is mainly studied in the paper, and there are two levels of topology for discussion. One level is topology of network layer which is the structure of network backbone, which describes routers, subnets and connections among them. The other one is topology of data link layer which is the structure in one subnet, which describes switches, hosts and connections among them.To obtain network topology information, it is necessary to use some protocols and tools. Some technologies and tools which have been widely used in topology discovery are introduced in the paper, and their merits, shortcomings and situation of being suitable for use are also discussed.At the network layer topology discovery, two algorithms in common use are introduced. The first is based on SNMP protocol, whose merits is simple and discovered quickly while the shortcoming is not suitable for wide use. The second is based on universal protocols, whose merits are supported in most situations, and shortcomings are too complicated and discovered slowly. An improved algorithm which synthesizes the two algorithms introduced before is presented in the paper. Through this algorithm, discovery process will be simple, high-effective, and have excellent applicability. Meanwhile, the problem of subnet discovering and how to identify a multi-address router is also solved.At the data link layer topology discovery, connections among switches are the most important. The discovery method of using FDB (Forwarding Database) is mainly studied in the paper. At present, the algorithm requires FDB should be more complete, and to implement is too complicated. Therefore, to overcome these shortcomings, an improved algorithm is presented. The improved algorithm can reduce reliance to FDB completion and make implement simpler. Meantime, the improved algorithm designs a scheme to solve the situation that there are some devices not supporting SNMP protocol during discovering.Finally, a prototype system based on these improved algorithms has been designed and implemented in the paper, in which system structure and key solution of prototype system has also been discussed. In real computer network environment, the prototype system has been tested. By analyzing the test result and comparing with other algorithms, the Correction and Feasibility have been proved.