Abstract: With IP level data collected from CAIDA， the characteristic of bottleneck in Internet was analyzed. Firstly， a statistical analysis about critical delay of network paths was made， which indicated that the bottleneck delay appeared in more than 80% network paths. And then a quantitative analysis on the bottleneck delay showed that the bottleneck made the similar network diameter’s network delay distinct. Furthermore， an analysis on IP addresses of the network delay and bottleneck delay from the degree of the geography location was performed， and it could be concluded that there was a big difference between network delay and bottleneck delay. Finally， a research on the causing of the bottleneck was made， which indicated that propagation delay was the main factor of the bottleneck delay for long distance， whereas the queue delay was the main factor for a short range.

Key words: bottleneck delay, Internet IPlevel, geography distance, propagation delay, queue delay