Doing More with Less: End-to-End Consistent IPv4 Address Sharing

The Internet is rapidly nearing IPv4 address space exhaustion. Current projections predict that within the next two years, all IPv4 address blocks will have been assigned. IPv6 adoption on the other hand has been slower than anticipated. It is becoming increasingly clear that there will be an extended period of during which both protocols will coexist as services and applications are slowly migrated to IPv6. As we transition from an Internet built on an abundance of IPv4 addresses to one of scarcity, innovative techniques that allow us to do more with less will become increasingly important. One such class of emerging techniques attempts to utilize unused port ranges to implement IP address sharing. We call this class of approaches Port Scavenging. In this paper we present a unique approach that allows multiple end hosts to share a single IPv4 address by relying on a modified device address resolution protocol. Our approach is fundamentally different from other techniques, as it does not require that packets from the end-host be modified at the network layer by an intermediate entity as they transit the network. Each end-host can use a valid routable public IP address. We have implemented our ideas in a modified Linux kernel to demonstrate the feasibility of our approach. Though not suitable for all environments, this technique can be a valuable addition to the IPv6 transition toolchest.