Direct Tunnel:
In the direct tunnel solution, one GPRS Tunneling Protocol (GTP) tunnel between the RNC and GGSN is used instead of the two user-plane tunnels between the RNC and SGSN, and the SGSN and GGSN. The SGSN does not need to forward user-plane data, which saves user-plane resources, reduces investment needs and operating expenses, and optimizes the user-plane performance of the PS domain of the UMTS core network.
Benefits:
- for carriers:
Saves user-plane resources of the SGSN and reduces investments and operating expenses in the 3G network.
Ensures easy upgrades to the EPC network by separating the control plane from the user plane.
Improves network expandability because user-plane expansion involves only the GGSN and RNC. - for subscribers:
This feature reduces user data delay and improves user experience.
Scenarios Where the Direct Tunnel Feature Is Not Applicable
- For roamers
- RNC/SGSN/GGSN does not support direct tunnel feature
- GGSN does not support GTPv1 ( GTPC v0 messages cannot carry the Direct Tunnel extension flag )
The carriers’ charging policy