n the PLMN and to schedule and deliver MBMS transmissions. The two distinct interfaces Gi and Gmb between GGSN and BM-SC are shown in the architecture model (Figure 8.4). The information on the Gi interface is routed to the device transparently via the GGSN, while information on the Gmb interface interconnects to the GGSN [9]. 8.2.1.5 Release 7 The 3GPP Release 7 introduces the concept of Direct Tunneling which enables a split between the control plane and user plane towards the packet core networks. In direct tunnel architecture, the SGSN controls mobility, authentication and control plane accounting to decide whether one or two tunnels are needed. When only one tunnel is created, the user plane traffic bypasses the SGSN making SSGN a signaling-only entity as shown in Figure 8.5. Direct Tunneling formerly known as "One Tunnel" approach offers a solution that optimizes Rel-6 PS core architecture without impacts to UE and can be deployed independently of the EPS architecture. Rel-8 TR 23.919 [10] further develops the One Tunnel approach described in Rel-4 TR 23.873 [11] and identifies what changes are needed to PS core and potentially to UTRAN functionalities and protocols to support the One Tunnel functionality [9]. All existing SGSN features (like MBMS, PS Handover, etc.) can co-exist with direct tunneling with the exemptions like (legal interception, Camel based pre paid service or charging only on S-Call Data Records) as payload is not passing through SGSN. The direct tunnel approach enables efficient handling of user plane traffic in the core network. Direct tunnel is a software feature that allows creating a tunnel directly between RAN and GGSN for user traffic. Since most of the traffic can be carried by standard IP routers and switches it not only simplifies the CN architecture but also provides savings to the operators. Another benefit of this approach is that operators no longer need to over-dimension SGSNs to guarantee safe delivery of user plane data. Direct tunnel technique can be also used in ATM net