Studies of existing P2P systems have shown that the architecture used can evolve over time (Gnutella). Although P2P systems set out to give all their nodes equal status, in reality this will never be totally achievable due to the different resources available to each node. These resources can range from network bandwidth, hard disc space, to processor power.
From studies of Gnutella it was observed that the nodes with more resources would move to the centre of the logical network and those with the least would move to the edge. This is understandable as the nodes with greater bandwidth are much more likely to act as routers to other nodes.