Internet Topology Discovery Using mrinfo

The Internet Group Management Protocol (IGMP - RFC1112) was initially designed to allow hosts to report their active multicast groups to the multicast router on their LAN. However, IGMP also provides some management tools such as the messages used by mrinfo. In practice, an mrinfo reply provides similar information as a show command on the router's command line interface. Therefore, mrinfo allows us to silently collect useful topological information.

The research community has developed many tools to try to map the topology of the Internet. As the Internet is a decentralised network composed of more thank 30000 different networks, it is very difficult (and perhaps impossible) to obtain a detailed map of the network. The most widely use to infer the router-level topology of the Internet is traceroute.