Cisco Cisco ASR 5000
Direct Tunnel
▀ Direct Tunnel Feature Overview
▄ SGSN Administration Guide, StarOS Release 18
Direct Tunnel Feature Overview
The direct tunnel architecture allows the establishment of a direct user plane (GTP-U) tunnel between the radio access
network equipment (RNC) and the GGSN/P-GW.
network equipment (RNC) and the GGSN/P-GW.
Once a direct tunnel is established, the SGSN/S-GW continues to handle the control plane (RANAP/GTP-C) signaling
and retains the responsibility of making the decision to establish direct tunnel at PDN context activation.
and retains the responsibility of making the decision to establish direct tunnel at PDN context activation.
Figure 24. GTP-U Direct Tunneling
A direct tunnel improves the user experience (for example, expedites web page delivery, reduces round trip delay for
conversational services) by eliminating switching latency from the user plane. An additional advantage, direct tunnel
functionality implements optimization to improve the usage of user plane resources (and hardware) by removing the
requirement from the SGSN/S-GW to handle the user plane processing.
conversational services) by eliminating switching latency from the user plane. An additional advantage, direct tunnel
functionality implements optimization to improve the usage of user plane resources (and hardware) by removing the
requirement from the SGSN/S-GW to handle the user plane processing.
A direct tunnel is achieved upon PDN context activation in the following ways:
3G network: The SGSN establishes a user plane (GTP-U) tunnel directly between the RNC and the GGSN,
using an Updated PDN Context Request toward the GGSN.