us make it possible to continue to connect more local switches and data sources to the backbone network. When the new routes have been tested and are working perfectly, we can remove more of the old routes from the local switches. See Figure A3.5. In this way we can, step by step, take more and more of the voice traffic through the ATM backbone network and reduce the traffic load on the tandem switches. Phase 3 At a certain stage in this process, when a big part of the voice traffic is routed through the ATM backbone network, it could be wise to introduce a second telephony server - for reliability reasons. See Figure A3.6. Phase 4 During this migration process there might be a need to expand the network with new subscribers. With this multi-service network solution it is possible to connect access nodes (AN) directly to the MSGs and thus there is no need to invest in any more local switches. See Figure A3.7. In modern access nodes it is possible to combine narrowband and broadband access, SO the operator can now also offer broadband services to subscribers who want this. Appendix 3: Development Tracks Router Router 12 LS's 12 LS's Router Router Figure A3.5 Second phase in the migration process Router Router 12 LS's 12 LS's Router Router Figure A3.6 Phase 3 in the migration process Understanding Changing Telecommunications - Building a Successful Telecom Business Router Router 12 LS's 12 LS's Router Router Figure A3.7 Phase 4 in the migration process Phase 5 In the process of replacing routes to the tandem switches with routes to the MSGs, we finally get to a stage where the tandem switches are not needed any longer. They can actually be taken away, and maybe be used somewhere else in the network. See Figure A3.8. Figure A3.9, where the tandem/transit switches have been removed, shows a network structure, which is very close to the vision, the packet-switched multi-service network. In the long run, the local switches will probably be replaced by access nodes. MIGRATION FROM ATM TO IP Today an ATM backbone network