SN (some may depend on the manufacturers road map) include: IPv6, mobility management, session management, QoS, multiple PDP context per IP address, tunnelling, charging, IPSec, lawful interception, SMS, pre-paid. 2 With UDI ISDN H.324 inter-working for example. The UMTS Development Platform 3.2.5.1.1 Functional Characteristics GPRS and the 3G SGSN As noted above, the 3G SGSN and the 2G SGSN do have some capital differences when it comes to functionality. If we pair them with the RNC and BSC, respectively, we can see the different functions in Table 3.1b. Table 3.1b The 2G- and 3G-SGSN functional characteristics 3G SGSN 2G SGSN Mobility management Interaction with HLR, MSC/HLR 3G MSC only Charging and statistics High capacity routing IP telephony Real time multimedia Authentication Radio protocol to IP conversion GTP tunnelling to GGSN Ciphering Compression While there remains similarities between the 2G/3G SGSNs, major differences also exist, e.g. ciphering and compression no longer takes place at the 3G SGSN but at the RNC. Mobility management takes place in the 3G SGSN and the RNC. Before, the BSC did not perform any of these functions. 3G SGSN will support delay sensitive ap- plications, e.g. IP telephony and real time multimedia requiring high capacity routing; these functions did not take place at the 2G SGSN. Thus, migration to the 3G SGSN has added some functions with demand for higher processing capacity. 3.2.5.2 The Gateway GPRS Support Node (GGSN) A 2G GGSN in most cases will not need structural changes besides probably a SW up- grade to support 3G. In any case, it acts as an interface between the GPRS/3G network and external networks. It connects the GPRS and 3G core to the Internet world, ISPs and private or corporate Intranets, thereby allowing 2G (GPRS) and 3G mobile users to have data services. On the other hand, because we see the GGSN as a router from exter- nal networks, major changes will occur only with additional unique functions. Other common functions, depending also on the manufacturer's 