IP (Internet Protocol) addresses identify devices on a network — like postal addresses for the internet. IPv4: 32-bit addresses like 192.168.1.1 — about 4.3 billion possible addresses (running out!) IPv6: 128-bit addresses like 2001:0db8::1 — virtually unlimited addresses In mobile networks, your phone gets an IP address when it establishes a PDU session (data connection). In 5G, this IP is assigned by the SMF/UPF.