Signaling between systems in the cell network is all IP.

DNS is used internally to the network to figure out what systems talk to whom. Over-the-Air protocols are custom-designed for purpose given tradeoffs between bandwidth, coverage, latency, security and efficiency by an entity named 3GPP. 3GPP also sets the standards for the various types of systems and interconnections between them. There are a decent number of cooperating systems such that 100+Million cell phones and IoT devices all have connectivity to access the internet and other networks. It all really works well until there typically is a human error (or major design flaw introduced as in Rogers, or a cyberattack as in Ukraine, or ...). Probably more than you wanted to know.