Stateful vs stateless NF design

Why Some NFs Are Inherently Stateful

Several 5GC NFs hold per-UE or per-session state that defines their function. AMF maintains the registration context for every connected UE — security context, served slices, last-known cell, paging state. SMF holds the PDU session context including allocated IP address, QoS rules, UPF binding, and timers. UDR/UDM persist subscriber data. UPF buffers user-plane packets and enforces packet detection rules. This state is not incidental; it is the function. An "AMF without UE context" is not an AMF. So when we talk about "stateless NF design" for these functions, we mean carefully decoupling the…