Migration phases
In Skype for Business Server 2019, you define sites on your network that contain Skype for Business Server 2019 components. A site is a set of computers that are well-connected by a high-speed, low-latency network, such as a single local area network (LAN) or two networks connected by a high-speed fiber optic network.
A Front End pool is a set of Front End Servers that are configured identically and work together to provide services for a common group of users. A pool provides scalability and failover capability to your users. Each server in a pool must run an identical server role or roles. A Standard Edition server, designed for small organizations, also defines a pool and runs on a single server. This enables you to have Skype for Business Server 2019 functionality for a lesser cost, but does not provide a true high-availability solution.
The following phases describe the process of a pool migration to Skype for Business Server 2019. For multiple sites containing multiple pools, each individual pool should follow this phased approach.