In this section, we describe how traffic makes its way from an application to the Internet. How it is treated depends on its type (IPv6, IPv4, TCP or UDP), its source, and its destination.

IPv6 from home network to IPv6 Internet

This traffic passes unaltered through the network. All home networks have global 2001::/16 prefix addresses and routing works as expected. There is no special treatment or translation of packets.

IPv6 from home network to IPv4 Internet

The IPv6 traffic to IPv4 services must be translated. We have opted for FAITH and NAT-PT. The former is a transport level connection translator, while the latter is a network level packet translator. While both translators are installed and operational, in practice, the transport level translator is used for daily use. The available NAT-PT implementation has a variety of non-trivial problems and does not seem ready for production use. It is installed and used in order to try to get a better understanding of its problems.

The problem with the faith implementation is that it only supports TCP. However, we have noticed that although there has not been support for UDPv4, no user request for it has been received. A lot of effort was saved this way. It is possible to add UDP support to FAITH and Invenia Innovation and the University of Tromsø have made an experimental implementation of such UDP support. This experiment was a successful proof-of-concept but further development needed for actual deployment was not performed due to limited interest compared to the effort involved and the number of problems to resolve. The most important application using UDP is DNS which is handled by the DNS proxy (Application Level Gateway). Most other UDP applications in use are multiparty games. At the moment there are few games with IPv6-capable clients that want to interoperate with their IPv4 counterparts.

In any way, DNS must be dealt with somehow in order for faith and NAT-PT to work transparently to the user. When a request is made, that results in an IPv4 address, the IPv6-only node would not know what to do with the result. To that end, we use the totd (Trick Or Treat) 6NET DNS proxy. This proxy needs to be accessible over both IPv4 and IPv6. Since the core is IPv6 only, this translation must occur at the “upper” edge of the network, i.e. at each home gateway.

Each home gateway then runs a totd DNS proxy, configured with the FAITH and/or NAT-PT network prefixes and the address of the ‘real’ recursive nameservers. In addition, the gateway is configured with a static route for these prefixes such that the traffic that requires translation is properly routed to the machines hosting the translators.