Unified communications as a service (UCaaS) is a cloud-delivered unified communications model that supports six communications functions:
Meetings (audio/video/web conferencing)
Instant messaging and presence (personal and team)
Communications-enabled business processes
UCaaS infrastructure is owned, operated, maintained and delivered by the provider. Typical characteristics include multitenancy (including tenant partitions residing on shared UC infrastructure, such as data centers, racks, compute, network, common equipment and blades) and self-service web portals for provisioning, management and performance/usage reporting. The provider delivers applications from a common platform and licenses the service for a monthly, recurring, subscription charge.