serving GPRS support node (GPRS) (SGSN)
The Serving GPRS Support Node (SGSN) is part of the packet-oriented GPRS network architecture. It provides the serving functions necessary for handling data traffic and uses several G interfaces, such as the Gb interface, which is used to exchange signalling information and subscriber data with the base station subsystem, or the Gn interface, which forms the transition to the gateway switching center (GSMC).
The Serving GPRS Support Node forwards IP packets destined for or sent by mobile stations in the SGSN coverage area. The tasks of an SGSN include routing and handover of packets into or out of the SGSN coverage area.
The node serves all mobile subscribers that are within the coverage area of the SGSN. In addition, the SGSN provides encryption and authentication, session and mobility management, and connectivity to the site directory( HLR), mobile switching center( MSC), base station controller ( BSC), and gateway GPRS support node ( GGSN).