  To measure the IPv6 internet AS-level topology, a network topology discovery
system, called Dolphin, was developed. By comparing the measurement result of
Dolphin with that of CAIDA's Scamper, it was found that the IPv6 Internet at AS
level, similar to other complex networks, is also scale-free but the exponent
of its degree distribution is 1.2, which is much smaller than that of the IPv4
Internet and most other scale-free networks. In order to explain this feature
of IPv6 Internet we argue that the degree exponent is a measure of uniformity
of the degree distribution. Then, for the purpose on modeling the networks, we
propose a new model based on the two major factors affecting the exponent of
the EBA model. It breaks the lower bound of degree exponent which is 2 for most
models. To verify the validity of this model, both theoretical and experimental
analyses have been carried out. Finally, we demonstrate how this model can be
successfully used to reproduce the topology of the IPv6 Internet.
