name: S4
full_form: Interface between SGSN and SGW for control plane
context: The Create Indirect Data Forwarding Tunnel Request message shall be sent on the S11/S4 interface by the MME/SGSN to the SGW as part of the Handover procedures or TAU/RAU procedure with Serving GW change and data forwarding as specified in clause 5.3.3.1A of 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3]. Table 7.2.18-1 specifies the presence requirements and the conditions of the IEs in the message. Table 7.2.18-1: Information Elements in a Create Indirect Data Forwarding Tunnel Request Table -2: Bearer Context within Create Indirect Data Forwarding Tunnel Request
description: The S4 interface is a critical control plane interface between the Serving GPRS Support Node (SGSN) and the Serving and Packet Data Network Gateway (SGW) in the Evolved Packet Core (EPC) architecture. It plays a vital role in managing data forwarding during handover procedures, Tracking Area Update (TAU), and Routing Area Update (RAU) with Serving GW change, as specified in 3GPP TS 23.401.
explanation: S4 is classified as an Interface because it facilitates communication between the SGSN and SGW for control plane operations, enabling efficient data forwarding and handover procedures within the EPC network.
section_title: 7.2.18 Create Indirect Data Forwarding Tunnel Request
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