Question: In a chained scenario involving S2a/S2b and PMIP-based S8 interfaces, how does the Serving GW handle uplink and downlink payload packets for a given PDN connection?
Option 1: The Serving GW drops all uplink packets from the S2a/S2b interface to prevent tunneling conflicts.
Option 2: The Serving GW routes downlink packets directly to the UE, bypassing the PMIPv6 GRE tunnels.
Option 3: The Serving GW forwards both uplink and downlink payload packets between the S2a/S2b PMIPv6 GRE tunnel and the S8 PMIPv6 GRE tunnel.
Option 4: The Serving GW aggregates all payload packets before transmitting them over a single, shared GRE tunnel.
Explanation: In a chained scenario where S2a or S2b interfaces are combined with a PMIP-based S8 interface, the Serving Gateway (Serving GW) acts as an intermediary. Its role is to ensure seamless communication by properly directing packets between tunnel endpoints for a specific PDN connection. The Serving GW forwards both uplink and downlink payload packets between the respective GRE tunnels of S2a/S2b and S8 interfaces, ensuring data reaches its destination without interruption, maintaining the integrity of the PDN connection across the chained interfaces.