IPv4 Address Sharing and Allocation for IPv6 Transition

摘要

A globally routable network address is critical to innovative Internet services and a great user experience. However, due to the rapid growth of Internet services and users, public IPv4 address space is unable to support the increasing demand. It's difficult to provide each subscriber with one public IPv4 address. The industry has made efforts toward IPv6 deployment, but the long-term coexistence of IPv4 and IPv6 is inevitable. Sharing IPv4 addresses is quite important for IPv4 service continuity when the Internet is smoothly transitioning to IPv6. The IETF proposes IPv4 address-sharing mechanisms, which will affect the network architecture especially in regards to addressing, routing, and forwarding during the transition period. This article discusses the principles of IPv4 address sharing, surveys the IPv4 address sharing and allocation mechanisms, and provides the recent standardization efforts in this area from the IETF.