SSC Mode Session and Service Continuity Mode
A 5G mode that governs how a PDU (Protocol Data Unit) Session is maintained, relocated or released as the UE (User Equipment) changes access or when the user-plane anchor, the UPF (User Plane Function) acting as the PSA (PDU Session Anchor), needs to change. The SSC mode is associated with a PDU Session at establishment and remains fixed for its lifetime. The SMF (Session Management Function) selects the mode based on the UE's request, the SSC mode selection policy in the UE's URSP (UE Route Selection Policy), subscription data and local configuration. SSC Mode 1 "anchor preserved", the PSA and IP address are retained for the session's lifetime regardless of UE movement, giving the strongest continuity but potentially sub-optimal routing. SSC Mode 2 "break-before-make", the network releases the session and IP address, then directs the UE to re-establish, allowing a new, better-placed anchor after a brief interruption. SSC Mode 3 "make-before-break", a new anchor is established before the old one is released, relocating the PSA without loss of connectivity, ideal for edge computing.
