Service providers also refer to converting the telephone service to Voice over IP (VoIP) due to disconnecting conventional telephone networks and implementing all-IP networks as migration. During this conversion, services to the end customer are to take place with as little impact on their equipment and with the least possible service interruption. To ensure that conventional analogue telephones, ISDN telephones or telephone systems can still be used with a Voice-over-IP connection, the internet access routers also work as analogue to VoIP adapters and provide conventional telephone connections for the end customer’s devices.
Different strategies are used depending on the migration to be performed. To ensure that migration remains manageable the ‘Chicken Little’ strategy uses several small, incremental individual steps executed successively. On the other hand there is the ‘Big Bang’ strategy which executes the actual conversion in one single, final step. First the new system is set up and tested alongside the old system. If the new system works properly, the old system is deactivated and the new system put into service in a ‘Big Bang’.
A migration must meet many requirements to be considered successful. It is crucial to ensure that the service is not be interrupted during the conversion, or with minimal interruptions. The amount of changes should therefore be as little as possible to minimise the risk of service interruptions. However, changes also need to be extensive enough to ensure the new system meets all requirements. A successful migration satisfies both conflicting requirements.