acm sigcomm

Control-plane protocols are complex in cellular networks. They communicate with one another along three dimensions of cross layers, cross (circuit-switched and packet-switched) domains, and cross (3G and 4G) systems. In this work, we propose signaling diagnosis tools and uncover six instances of problematic interactions. Such control-plane issues span both design defects in the 3GPP standards and operational slips by carriers. They are more damaging than data-plane failures. In the worst-case scenario, users may be out of service in 4G, or get stuck in 3G.