This chapter briefly describes the 3G UMTS direct tunnel feature, indicates how it is implemented on various systems (for example, the Serving GPRS Support Node (SGSN), the Gateway GPRS Support Node (GGSN), and the Home NodeB Gateway (HNB-GW), and provides feature configuration procedures. Direct tunnel is an enhanced feature, so some products may require a feature implementation license and all relevant products will require completion of basic service configuration. Refer to your product’s administration guide for feature licensing and basic service configuration information.
Important: This chapter provides a limited instruction set for configuring direct tunnel. Basic service configuration for the SGSN is provided in the
SGSN Service Configuration Procedures chapter of the
SGSN Administration Guide. Command details are provided in the Command
Line Interface Reference.
The direct tunnel architecture allows the SGSN to establish a direct user plane tunnel between the radio access network (RAN) and the GGSN. Once a direct tunnel is established the SGSN continues to handle the
control plane signaling. This improves the user experience (e.g., expedites web page delivery, reduces round trip delay for conversational services). Additionally, direct tunnel functionality implements the standard
SGSN optimization to improve the usage of user plane resources (and hardware) by removing the requirement from the SGSN to handle the user plane processing.
By default, direct tunnel support is disallowed on the SGSN and allowed on the GGSN. The SGSN’s direct tunnel functionality is enabled within the SGSN operator policy configuration.