PFQDN: SDN- and DNS-Assisted Transparent Communications Among Behind-NAT Networks

It is common knowledge that network address translation (NAT) is the most economical means of deployment large-scale users to access the IPv4-based Internet, which could be combined with a few, even single public IP addresses. Although the NAT issues do not catch more attention from the research community, it does not mean they are unimportant to modern network deployments, e.g., fifth-generation (5G) and Internet of Things (IoT). This article introduces a structured transparent communications service framework among NATed subdomains, consisting of software-defined networks and an authoritative domain name system. Through addressing via the private fully qualified domain name, the above components coordinate and provide bidirectional interconnect capability among NAT-enabled intranets. In other words, each internal host with a private IP address has a dedicated corresponding PFQDN on the outside. The proposed scheme emphasizes availability: which extends the IPv4 address space from 2
³²
to 2
⁵⁶
or even more; but at the expense of performance: which restricts the concurrent quantity of reverse connections during a time period (depending on the quantity of available public IP addresses). The proposed scheme features a high potential to solve the NAT traversal problems for Internet services and applications that may encounter IPv4 address exhaustion on the current Internet.