Section: L.4 C-SGN
Content: The C-SGN (CIoT Serving Gateway Node) is a combined node EPC implementation option that minimizes the number of physical entities by collocating EPS entities in the control and user planes paths (e.g. MME, S-GW, P-GW), which may be preferred in CIoT deployments. The external interfaces of C-SGN implementation option are the interfaces of the respective EPC entity supported by the C-SGN, such as MME, S-GW, and P-GW. A C-SGN supports sub-set and necessary functionalities compared with the existing EPS core network elements and also supports at least some of the following CIoT EPS Optimisations: - Control Plane CIoT EPS Optimisation for small data transmission. - User Plane CIoT EPS Optimisation for small data transmission. - Necessary security procedures for efficient small data transmission. - SMS without combined attach for NB-IoT only UEs. - Paging optimisations for coverage enhancements. - Support for non-IP data transmission via SGi tunnelling and/or SCEF. - Support for Attach without PDN connectivity.