Question: In a PMIPv6-based mobility setup, what is used for multiplexing and demultiplexing traffic of different PDN connections at the Mobility Access Gateway (MAG) and Local Mobility Anchor (LMA)?
Option 1: Different, per-interface, per-PDN connection, per-direction (uplink and downlink) Generic Routing Encapsulation (GRE) keys
Option 2: Shared, global GRE keys for all PDN connections
Option 3: Dynamic Host Configuration Protocol (DHCP) identifiers
Option 4: IP-in-IP encapsulation with source IP differentiation
Explanation: In a PMIPv6 setup, to efficiently manage multiple PDN connections and ensure proper routing of traffic, different GRE keys are utilized. These keys are specific to each interface, each PDN connection, and differentiate between uplink and downlink traffic. This approach enables the MAG and LMA to correctly multiplex (combine) and demultiplex (separate) traffic belonging to various PDN connections, ensuring data integrity and proper delivery.