On the Scalability of Addressing in Private Networks Using RPX

Abstract

In recent times, the imminent lack of public IPv4 addresses has attracted the attention of both research community and industry. The cellular industry has decided to combat this problem by using IPv6 for all new terminals. However, the success of 3G network deployment will depend on the services offered to end users. Currently, almost all services reside in the public IPv4 address space, making them inaccessible to users in IPv6 networks. Thus, an intermediate translation mechanism is required. Previous studies on network address translation methods have shown that REBEKAH-IP with Port Extension (RPX) supports all types of services that can be offered to IPv6 terminals from the public IPv4 based Internet, and provides excellent scalability. However, this method suffers from an ambiguity problem which may lead to call blocking. In this paper, we present an improvement to RPX scheme in which the side effect is removed and fully scalable system. We firstly show the expected number of public IPv4 addresses utilization to the DNS of RPX server. This utilization is computed in terms of the probability of socket open requests from mobile terminals, the probability of call blocking and the estimated number of mobile terminals at the network initialization phase. The mathematical model is also provided as a guideline to determine the range of public IPv4 addresses allocated to an RPX gateway in a cellular network. In addition, the results are presented through a set of simulations. However, we proposed the RPX scheme to use a simple round robin scheduling algorithm is sub-optimal in terms of call blocking probability and further propose to use a priority queue algorithm to improve the scalability. In addition, we present extensive simulation results on the practical scalability of RPX with different traffic compositions to provide a guideline of the expected scalability in large-scale networks such as 3G networks.

Keywords