  Although many classical IP geolocation algorithms are suitable to
rich-connected networks, their performances are seriously affected in
poor-connected networks with weak delay-distance correlation. This paper tries
to improve the performances of classical IP geolocation algorithms by finding
rich-connected sub-networks inside poor-connected networks. First, a new
delay-distance correlation model (RTD-Corr model) is proposed. It builds the
relationship between delay-distance correlation and actual network factors such
as the tortuosity of the network path, the ratio of propagation delay and the
direct geographical distance. Second, based on the RTD-Corr model and actual
network characteristics, this paper discusses about how to find rich-connected
networks inside China Internet which is a typical actual poor-connected
network. Then we find rich-connected sub-networks of China Internet through a
large-scale network measurement which covers three major ISPs and thirty
provinces. At last, based on the founded rich-connected sub-networks, we modify
two classical IP geolocation algorithms and the experiments in China Internet
show that their accuracy is significantly increased.
