Figure A3.1 A common target network is assumed for different types of operators Understanding Changing Telecommunications - Building a Successful Telecom Business. Edited by A. Olsson © 2004 John Wiley & Sons, Ltd ISBN: 0-470-86851-1 Understanding Changing Telecommunications - Building a Successful Telecom Business The migration strategy is also a matter of actor competence. A gradual migration facilitates the actor task to manage the competence issue, keeping pace with the new technology, new processes and possibly new organization. OBJECTIVES The main objective of this appendix is to make the vertical to horizontal network migration process more concrete to the reader by means of illustrating a stepwise migration towards a target network for an incumbent operator. It is assumed that the target network is fairly common for different actors. 'All roles go for multi-service and multimedia' (Chapter 4, Figure 4.25). In this appendix we will therefore look at the left path of Figure A3.1, corresponding to an incumbent operator. The figure uses some expressions that might need clarification. Voice trunking means some kind of packetized transfer of voice in the trunk (= inter- exchange) network. Whether or when to use ATM or IP is under debate. For fixed voice centric operators migration experience is becoming increasingly available, which is the basis for this appendix. Internet offload in the right path in the figure means that the data/Internet calls over modems in telephony networks are extracted from the telephony network. In the following we will describe, in a simplified and pedagogical way, a possible migration of an existing circuit-switched telephony network into a packet-switched ATM based multi-service network. TARGET NETWORK Figure A3.2 shows a target connectivity network vision, exemplifying the future packet- switched multi-service network. Local switches, access nodes, enterprises, servers etc. are connected via multi-service gateways (MSG) to a common connectivity network. In this context 'service' me