This paper started with discussing the developing of Internet. First, we have discussed several questions which IPv4 is facing, such as the limit of IPv4 address space, the increasing size of the routing tables, the absence of QOS.

• 本文从Internet的发展谈起，讨论了目前IPv4所面临的几个主要问题：(1)地址空间的不足； (2)路由表过于庞大；