PF 41-packet forwarding for seamless use of IPv6 devices behind IPv4-only NAT gateways

This paper describes a PF (protocol field) 41-packet forwarding mechanism for seamless use of IPv6 devices behind IPv4-only NAT (network address translation) gateways. The PF 41-packet forwarding enables IPv6 nodes to set-up symmetric end-to-end connections with other IPv6 nodes located behind an IPv4-only NAT gateway. The symmetry, meaning both outgoing as well as incoming connections are possible, is one of the most important requirements for proper functioning of peer-to-peer applications like A/V conferencing, IP telephony and multi-user gaming.