An Empirical Study of Global RCS Deployments

Abstract

Rich Communication Services (RCS) is the mobile industry's answer to increasingly popular over-the-top (OTT) instant messaging applications such as WhatsApp, iMessage, and Signal. RCS is a successor to SMS and MMS that adds many modern messaging features expected from OTT messaging applications, but not available with SMS and MMS. RCS adoption has gained traction, driven by the GSMA's mandate for 5G user equipment and Apple's adoption, bringing RCS to a large group of new users. Despite the growing importance of this technology, there is little public, empirical data on the current deployment landscape. This thesis presents an empirical study of global RCS deployments along three axes. First, we measure the RCS autoconfiguration ecosystem by querying more than three million candidate configuration-server domains and classifying the responding deployments by hosting provider and implementation. Second, we analyze configuration documents from a chosen set of providers, assessing their specification compliance and security aspects. Finally, we use a capability discovery mechanism to determine which features different clients and operators support and how they differ across them. Our results show that current RCS infrastructure is highly centralized, with 98% of deployments being hosted on Google's Jibe cloud platform. We further find multiple specification-related inconsistencies in configuration documents. Our analysis of advertised client capabilities reveals that the client implementations associated with an arbitrary phone number can be identified through the set of announced features.