Cisco Cisco ASR 5000
Direct Tunnel
▀ Direct Tunnel Feature Overview
▄ SGSN Administration Guide, StarOS Release 18
3. Direct Tunneling - LTE Network, S12 Interface
A major consequence of deploying a direct tunnel is that it produces a significant increase in control plane load on both
the SGSN/S-GW and GGSN/P-GW components of the packet core. Hence, deployment requires highly scalable
GGSNs/P-GWs since the volume and frequency of Update PDP Context messages to the GGSN/P-GW will increase
substantially. The SGSN/S-GW platform capabilities ensure control plane capacity will not be a limiting factor with
direct tunnel deployment.
the SGSN/S-GW and GGSN/P-GW components of the packet core. Hence, deployment requires highly scalable
GGSNs/P-GWs since the volume and frequency of Update PDP Context messages to the GGSN/P-GW will increase
substantially. The SGSN/S-GW platform capabilities ensure control plane capacity will not be a limiting factor with
direct tunnel deployment.
The following figure illustrates the logic used within the SGSN/S-GW to determine if a direct tunnel will be setup.