  A number of recent studies of the Internet topology at the autonomous systems
level (AS graph) are based on the BGP-based AS connectivity maps (original
maps). The so-called extended maps use additional data sources and contain more
complete pictures of the AS graph. In this paper, we compare an original map,
an extended map and a synthetic map generated by the Barabasi-Albert model. We
examine the recently reported rich-club phenomenon, alternative routing paths
and attack tolerance. We point out that the majority of the missing links of
the original maps are the connecting links between rich nodes (nodes with large
numbers of links) of the extended maps. We show that the missing links are
relevant because links between rich nodes can be crucial for the network
structure.
