 to support your business objectives. Technical criteria: Select your points of interconnection to suit your business idea in the best possible way. In a real interconnection situation, the two interconnecting operators may have to include both national and sometimes regional (e.g. EU) laws and regulations into the agreement. Commercial criteria Technical criteria Service criteria Figure 15.8 Main parts of a service interconnection agreement Understanding Changing Telecommunications - Building a Successful Telecom Business A good help during the interconnection negotiations (at least in Europe) would be to consult the checklist 'Framework Interconnect Agreement' produced by the European Telecom Platform. The original definition of an SLA is: The SLA is a legal contract between a service provider and a customer that specifies, usually in measurable terms, what services the service provider will furnish. It defines also the consequences (penalties) if the service provider fails to deliver the specified services according to the specified conditions. This means that all users/subscribers indeed are embraced by an SLA. Today SLA also has a wider interpretation that covers contractual obligations in many types of interfaces, for example between two network operators. For such an interface much of the content in fundamental technical plans is relevant. Apart from technical parameters the monetary interconnection conditions are important. SLA is a cornerstone in establishing end-to-end QoS and security. Call termination/interconnect of data services is a big unresolved issue. For voice ser- vices call termination/interconnect is typically 25-30 % of total revenue. It will probably be a much lower percentage for Internet-based services. How do you charge for something that was free to send? 15.6 SERVICE INTERWORKING 15.6.1 VIRTUAL HOME ENVIRONMENT In mobile systems like GSM, the home mobile network does not control the services when the subscriber roams to a visited PLMN. Instead, service information is transferred from 