Implementing NAT traversal with Private Realm Gateway

A Network Address Translator (NAT) allows hosts in a private address space to communicate with servers in the public Internet. There is no accepted solution for an arbitrary host in the Internet to initiate a communication with a host located in a private address space despite the efforts to create one. This paper proposes to replace NATs with a new concept we call Private Realm Gateway (PRGW). Private Realm Gateway creates connection state based on incoming DNS queries towards the hosts in the private network. The state gives means for the private network operator to apply elaborate access control to packet flows arriving from the Internet to the private network. PRGW does not require changes in the hosts and the deployment can take place one network at a time. The paper shows that the PRGW is most applicable for connecting mobile and other wireless hosts to the Internet.