Impact of Carrier-Grade NAT on Web Browsing

International audiencePublic IPv4 addresses are a scarce resource. WhileIPv6 adoption is lagging, Network Address Translation (NAT)technologies have been deployed over the last years to alleviateIPv4 exiguity and their high rental cost. In particular, Carrier-Grade NAT (CGN) is a well known solution to mask a wholeISP network behind a limited amount of public IP addresses,significantly reducing expenses.Despite its economical benefits, CGN can introduce connectivityissues which have sprouted a considerable effort in research,development and standardization. However, to the best of ourknowledge, little effort has been dedicated to investigate theimpact that CGN deployment may have on users’ traffic. Thispaper fills the gap. We leverage passive measurements froman ISP network deploying CGN and, by means of the Jensen-Shannon divergence, we contrast several performance metricsconsidering customers being offered public or private addresses.In particular, we gauge the impact of CGN presence on users’web browsing experience.Our results testify that CGN is a mature and stable technologyas, if properly deployed, it does not harm users’ web browsingexperience. Indeed, while our analysis lets emerge expectedstochastic differences of certain indexes (e.g., the difference inthe path hop count), the measurements related to the qualityof users’ browsing are otherwise unperturbed. Interestingly, wealso observe that CGN protects customers from unsolicited, oftenmalicious, traffic.