SCTP (Stream Control Transmission Protocol): A transport protocol designed for telecom signaling. Combines the reliability of TCP with message boundaries (like UDP). Supports multi-homing (multiple IP addresses) for redundancy. Used for: • NGAP: gNB ↔ AMF (N2 interface) in 5G • S1AP: eNB ↔ MME (S1 interface) in 4G • Diameter over SCTP in some deployments