A Technique for Counting NATted Hosts

There have been many attempts to measure how many hosts are on the Internet. Many of those end-points, however, are NAT boxes (Network Address Translators), and actually represent several different computers. We describe a technique for detecting NATs and counting the number of active hosts behind them. The technique is based on the observation that on many operating systems, the IP header's ID field is a simple counter. By suitable processing of trace data, packets emanating from individual machines can be isolated, and the number of machines determined. Our implementation, tested on aggregated local trace data, demonstrates the feasibility (and limitations) of the scheme

Random Number Generation: Types and Techniques

What does it mean to have random numbers? Without understanding where a group of numbers came from, it is impossible to know if they were randomly generated. However, common sense claims that if the process to generate these numbers is truly understood, then the numbers could not be random. Methods that are able to let their internal workings be known without sacrificing random results are what this paper sets out to describe. Beginning with a study of what it really means for something to be random, this paper dives into the topic of random number generators and summarizes the key areas. It covers the two main groups of generators, true-random and pseudo-random, and gives practical examples of both. To make the information more applicable, real life examples of currently used and currently available generators are provided as well. Knowing the how and why of a number sequence without knowing the values that will come is possible, and this thesis explains how it is accomplished