National National Regional Aggregation Site router router router Region A/Operator A Region B/Operator B Voice transferred on top of RTP/UDP/IP/MPLS Figure 15.4 Example of two alternative connection paths between two MGWs in two intercon- nected core networks based on IP transport. Alternative paths create reliability Marketing expenses, Business Total market Competitors pricing (all users) and cooperating roles User needs Revenue User segments (Other operators Market share, churn and service (Regulations) providers, content providers etc.) Service offerings Operating expenses Financial Interconnect calculations, ROCE, NPV ROI, risk Investments Network Accounting Figure 15.5 Position of an interconnect plan with vertical interconnect that specifies agreements and important mutual information. Because of all the possible roles according to Chapter 4, there is a need for many other interconnect plans as well Interconnection Obviously, if there is an efficient and relevant communication and written agreements between B and C, things should work. What type of communication is then relevant? Let us call it an interconnection plan or an interworking plan and integrate it among our fundamental plans. The position is seen in Figure 15.5. Not surprisingly, it turns out that the plan contains most of the other plans. Interfacing gateway locations and the values in the interfaces between the actors must be clearly defined. See also the paragraph on reference points below. 15.3 INTERCONNECTION IN TELE-CENTRIC FIXED VOICE NETWORKS Critical issues are: Point of interconnect (POI) Services Subscriber access Number portability Charges and payments Billing Numbering Signalling and interface standards Network design and routing principles (e.g. emergency) Synchronization Network management, installation, operation and maintenance Obviously the issues deal mainly with fundamental technical plans. It should be noted that mobility management has to be added for mobile networks, and security and QoS for the network dealt with in this 