A Queueing Theoretic Analysis of Source IP NAT

Abstract

The number of devices connected to the Internet has outstripped the number of effectively assignable IPv4 addresses. In order to be globally reachable, many devices must share the same IPv4 address; current mechanisms only provide reachability when the device sharing the IPv4 address itself initiates communication. We describe a mechanism to make nodes behind a NAT globally reachable, even when communications are initiated from the global Internet. The intended application of the mechanism, denoted SIPNAT, is to allow for the first time bidirectional global reachability of IPv6 addresses by nodes in the global IPv4 Internet, in a scalable manner, thus resolving the major issue associated with IPv4-IPv6 translation. SIPNAT involves filtering flows at the gateway between the IPv4 and IPv6 domain through a combination of DNS request and timing information for the IPv4 initiated connection (the IPv6 to IPv4 connections are performed using typical NAT mechanisms, where the IPv6 domain takes the role of the private address space). We study the performance of the SIPNAT mechanism using queuing theoretic analysis, and show that our SIPNAT model is accurate on actual data traces.