rnets, Intranets, and Extranets Chapter 7 The combination of the packet switching technologies (X.25 and IP) make the transfer of data communications a smooth operation in today's networks. Although X.25 has waned in its popularity, it is still used throughout the world in emerging countries that have older networks in place. The use of IP makes use of the connectionless transfer of data more robust and simplifies its implementation. Nearly every computer manufac- turer today has embedded IP in the os as a core protocol element. GPRS takes advantage of the standard interfaces that have evolved over the years to support the packet data networks through these simple inter- faces. That way, GPRS can be implemented as an on-ramp service to a pub- lic data network, rather than having to build a whole new architecture or set of protocols. Having spent the time to consider the use of public X.25 networks and the Internet, coupled with the intranet and extranet, we now have a basis on which the applications can be supported from a hand-held wireless interface. In Chapter 11, "Future Enhancements and Services," these applications of the intranet and Internet integartion culminate in some of the application-specific uses for GPRS in the future. 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. CHAPTER Mobile Station to SGSN Interface Mobile Station to SGSN Interface Chapter 8 Objectives Upon completion of this chapter, you should be able to Understand the way the mobile station communicates with the SGSN via LLC. Discuss the ways the data protocols work at Layer 2 and 3. Describe the use of SNDCP protocols. Understand the services that the SGSN offers to the mobile station. Describe how the protocols stack up. Describe the use of the TLLI. Logical Link Control (LLC) Layer The Logical Link Control (LLC) layer provides a reliable logical link between the 