The meet-in-the-middle network provides a simple way to restore end-to-end connectivity between distant hosts located behind network address translators, and does so without reconfiguring the NAT devices that lie on the path between the hosts.
Citation:
Atsushi Kara, "Private-to-Private Communications over the Internet," Computer, vol. 37, no. 5, pp. 53-59, May 2004, doi:10.1109/MC.2004.1297242