Multi-edged network address translation - protocol translation

Abstract

IPv6 is a new version of the internetworking protocol designed to address the scalability and service shortcomings of the current standard, IPv4. Since, IPv6 is not compatible with IPv4, programs and systems based on one protocol cannot communicate with those based on the other. Consequently, it is necessary to develop a smooth transition mechanism that enables applications to continue working while the network is being upgraded. There have proposed several transparent transition services that translate packet headers as they cross between IPv4 and IPv6 networks. Network Address Translation-Protocol Translation(NAT-PT) is one of such transition mechanisms that have been proposed. However, NAT-PT has a topology limitation that each IP session between an IPv6 host and an IPv4 host must be routed through the same NAT-PT router, as the NAT-PT router maintains the state information for sessions established through it. It is often suggested that NAT-based routers be operated on a border router unique to a stub domain, where all IP packets are either originated from the domain or destined to the domain. However, such a configuration would turn a NAT router into a single point of failure. Besides, if the NAT-PT router is heavily utilized, it may become a performance bottleneck. These problems can be removed by using multiple NAT-PT routers. We have developed two different methods. One is Packet Forwarding via Multicast(PFM). Every NAT-PT router in a stub domain joins IPv4 and IPv6 multicast groups, and sends packets to the group when no mapping state exists in the address mapping table. The other is Sharing Mapping States (SMS). Every NAT-PT router in a stub domain shares their mapping states by sending special mapping information packets to other routers using Mapping States Distribution Protocol (MSDP). We propose one outstanding mechanism which is most effective in terms of performance. We evaluated the performance by formulas under predefined network model....