DNS (Domain Name System): Translates human-readable names (google.com) to IP addresses (142.250.80.46). Without DNS, you'd have to memorize IP addresses for every website. DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses to devices joining a network. In mobile networks, the core network (SMF in 5G) handles IP assignment instead. NAT (Network Address Translation): Allows many devices to share one public IP address. Your home router uses NAT — all your devices appear as one IP to the internet.