  We show that the Internet topology at the Autonomous System (AS) level has a
rich--club phenomenon. The rich nodes, which are a small number of nodes with
large numbers of links, are very well connected to each other. The rich--club
is a core tier that we measured using the rich--club connectivity and the
node--node link distribution. We obtained this core tier without any heuristic
assumption between the ASes. The rich--club phenomenon is a simple qualitative
way to differentiate between power law topologies and provides a criterion for
new network models. To show this, we compared the measured rich--club of the AS
graph with networks obtained using the Barab\'asi--Albert (BA) scale--free
network model, the Fitness BA model and the Inet--3.0 model.
