aggregate behaviour that enables delivery of service at agreed levels. The policy itself may be stored in a directory. Mobility agent. This function provides support for handling personal mobility, terminal mobility and service mobility. Interconnection 15.1 OBJECTIVES To explain: what is meant by interconnect and interworking relationships between interworking and fundamental technical plans interconnect and roaming, roaming between technologies interconnect and VHE interconnect and e2e performance interconnect and signalling interconnect and charging and accounting interconnect and SLA the need for cooperation between technologies, such as UMTS and WLAN. Figure 15.1 gives a hint on involved areas. Media/border gateway control function Other networks Terminal Service network or home network if any Applications Service enablers Roaming Mobility management (PDP context) network control and intelligence IW signalling Border Access Core connectivity gate- Connectivity Might be visited network Figure 15.1 Dedicated interworking parts of the reference model - in a particular call other 'ordi- nary' parts will be involved as well Understanding Changing Telecommunications - Building a Successful Telecom Business, by A. Olsson © 2003 Ericsson och Student litteratur. ISBN: 0-470-86851-1 Understanding Changing Telecommunications - Building a Successful Telecom Business 15.2 INTRODUCTION It has been said before: it is the user perception that counts. The main user perceived areas in this book are services, QoS and security, all perceived end to end. The strong relationship between interconnect and user perception is therefore obvious. In Europe the EC sees interconnection as a key element in the future competitive environment, allowing new market entrants access to existing end users, on a basis that will encourage increased investment and market growth in the telecommunications sector. Among the main interconnection/interworking success factors are roaming or 'remote service access' including virtual home environment (VHE)