Method Of Internet Topology Discovery

Capturing the Internet topology is very important as it can be used to design and evaluation of new protocols and services.Internet topology has the characteristics of heterogeneity,diversity and dynamic,which makes it difficult to obtain the accurate network topology.The network topology discovery technology is mainly used to detect the unknown network topology and discovery the topology of the network automatically.According to the network protocol,network topology can be divided into two categories:switch level and router level.Switch level is mainly for Ethernet topology,and router level is mainly for the subnet or Internet topology.In this thesis,the network topology is inferred from the delay which measured by end-to-end.Due to the large scale of Internet network,it is difficult to deploy a large number of probe hosts for delay measurement.Considering the existence of many terminals in the Internet,and most of them open TCP(Transmission Control Protocol)port,the three-way handshake in TCP is used to measure the delay from host to each node in the path in this thesis.By constructing the probe packet group,making full use of the TTL(Time To Live)field in IP(Internet Protocol)packet,the delay from host to each node in the path is measured.And constructing two sets of packets with different destination,the delay of the shared path from the two terminals to host is measured.According to the delay of the shared path and the delay of each node in the path,the nearest parent node of two terminals in the topology tree is deduced.Running the nearest parent algorithm for each terminal,network topology tree can be inferred.In order to improve speed of the delay measurement which is time consuming task,a centralized multi-host detection scheme is designed in this thesis.In this thesis,a distributed host is used to make the route of packet as much as possible,so that the topology of the mesh network can be deduced.Comparing the topology tree obtained by distributed host,we can judge whether there is a ring in the topology tree and infer the position of ring.Finally,the correctness of the proposed scheme and the completeness of the inferred topology are verified in the simulation platform.The experimental environment is set up in the simulation platform,and then the scheme is applied in it.Comparing the number of nodes and links inferred by experiments,to show the improvement of completeness in this thesis.