ll Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. System Architecture Chapter 3 packets. Additionally, a type field in which the PDU type is specified and a QoS parameter is included. Three routing protocols are available: Static Open Shortest Path First (OSPF) Layer 2 subnetwork architectures that may be used below IP include Ethernet Token Ring Fiber-Distributed Data Interface (FDDI) Integrated Services Digital Network (ISDN) GPRS will support interworking of mobile stations with IP first and X.25 later. Further, GPRS will transmit the corresponding PDU transparently by encapsulation and decapsulation. The G interface between Public Land Mobile Network (PLMN)/GPRS and the Intranet/Internet Service Provider (ISP) is carried out via the pub- lic network. IP Security (IPSec) protocols may be used to provide authenti- cation and encryption of the link. This enables confidential transport of the G interface over the public domains such as the Internet. Initial Implementations The first releases of GPRS products must support IP and interworking with the Internet and intranets. Figure 3-9 shows a view of the initial imple- mentation networks. Only one SGSN will be required due to the relatively low number of users in North America. Interconnection between GGSN and GSM/NSS nodes (MSC/VLR, HLR, and SMSC) requires a Signaling System Number 7 (SS7)/IP gateway, or SIG, to link the IP backbone with G5, G1, and Gd interfaces. To manage IP addresses, a server that contains the following functions will be used: Domain Name Server (DNS) To translate domain names to IP addresses and vice versa Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. System Architecture System Architecture Figure 3-9 PSTN/ Initial implementations. SS7/IP Internet Gateway & DMS Agprs Private IP Intranet Backbone PCUSN OMC-C Charging Int