Deploying Carrier Grade NATs (CGNs) enables Mobile Broadband Network Operators (MNOs) to provide Internet access services to a very large number of customers with a limited amount of public IP addresses. However, CGNs impose a number of functional and potentially performance penalties. In the project we have developed a measuring tool, called CGNWatcher that executes a number of active tests to fully characterize CGN deployments in MNOs. The CGNWatcher tool systematically tests more than 30 behavioural requirements of NATs defined by the Internet Engineering Task Force (IETF) and also multiple CGN behavioural metrics.
We have deployed CGNWatcher in MONROE and performed large measurement campaigns to characterize the real CGN deployments of the MNOs serving the MONROE nodes. The tool was designed to easily allow future features to easily be integrated.
As part of the project, we characterize roaming across Europe for 16 different MNOs deployed in six countries. The goal of the experiment was to try to understand if the MNO changes CGN while roaming, for this reason, we run a series of measurements that enable us to identify the roaming setup, infer the network configuration for the 16 MNOs that we measure and quantify the end-user performance for the roaming configurations which we detect.
The measurement results obtained through CGNWatcher are relevant to application and protocol developers to inform their design about how to overcome the limitations imposed by CGNs. The information retrieved through CGNWatcher are also useful for experimenters using MONROE, as CGNs may have an important impact in the feasibility of experiments and can potentially bias the results if not accounted for.
Moreover, we will disseminate the results through academic publications in the next months and we will promote the adoption of the proposed metrics in the IETF in order to obtain a standardized set of metrics for CGN characterization. Results from roaming have been accepted to be published in the 24th Annual International Conference on Mobile Computing and Networking (MobiCom ’18).