Question: In a GTP-U Tunnel, what is the primary purpose of the Tunnel Endpoint ID (TEID) in the GTP header?
Option 1: To specify the maximum transmission unit (MTU) size for the inner IP packet.
Option 2: To identify the Access Point Name (APN) for routing decisions.
Option 3: To multiplex and de-multiplex packets between a given pair of GTP-U Tunnel Endpoints.
Option 4: To signal the control plane protocol version used (e.g., GTPv1-C, GTPv2-C).
Explanation: The TEID is crucial for identifying which tunnel a particular T-PDU belongs to, enabling the multiplexing and de-multiplexing of packets between two specific GTP-U Tunnel Endpoints. This ensures that packets are correctly routed within the network, highlighting the importance of TEID in managing multiple tunnels efficiently.