The GPRS system must provide means of transmission in the user plane between the MS and external data packet network, according to the QoS related to a PDP context and the interface constraints of the PLMN. Despite the variety of interfaces across the GPRS network, the system must ensure an end-to-end transmission path.
This chapter deals with the user plane between the MS and the accessed external packet network. Protocols such as subnetwork dependent convergence protocol (SNDCP), LLC enable IP PDUs to be conveyed between the MS and the SGSN in acknowledged or unacknowledged modes. The user plane between the MS and SGSN is described in Section 8.1. As for the GTP layer line, it carries the IP PDUs within the GPRS backbone network. The user plane within the backbone network is described in Section 8.2. The user plane related to the air interface and Gb interface is covered in Chapters 5 and 6, respectively. Scenarios for IP sending within the GPRS PLMN are provided in Section 8.3.
A GPRS PLMN interconnects with an external data packet network. Interworking is described in Section 8.4.