Due to the depletion of the global IPv4 address pool, the internet service providers will be able to supply their new clients with IPv6 addresses only in the near future. The application of the DNS64 and NAT64 technologies can enable the IPv6 only clients to communicate with the still dominant IPv4 only servers. However, the clients of certain applications such as HTTP and FTP use multiple sessions and thus they consume multiple ports. This phenomenon may cause a lack of ports situation at the NAT64 gateway. Therefore the port consumption of the different applications is an important design parameter of the NAT64 gateways. In this paper, the port consumption of different NAT64 compatible applications was measured. It was also determined what factors can influence the port consumption of a web or an ftp client. The detailed description of our measurement method is given. Our results can give a valuable help for careful design and configuration of a NAT64 gateway.

The proliferation of smart phones and other Internet capable devices together with the depletion of the global IPv4 address pool will be a huge driving force for the deployment of IPv6 in the forthcoming years. The communication of an IPv6 only client with an IPv4 only server is a typical practical task to be solved among the many issues of the co-existence of IPv4 and IPv6. The usage of DNS64+NAT64 may be a good solution if our applications can flawlessly work with it. As for NAT64 implementations, TAYGA running under Linux and Packet Filter (PF) of OpenBSD were tested with the following application level protocols: HTTP, HTTPS, SMTP, POP3, IMAP4, Telnet, SSH, FTP, OpenVPN, RDP, Syslog, BitTorrent, Skype and SIP. The client-server application protocols could traverse through the NAT64 gateway flawlessly but the peer to peer ones failed. In contrast to the results of other researchers, OpenVPN worked perfectly with NAT64.