CUCM

Cisco Unified Communications Manager (CUCM) is the core call-processing component of Cisco's Unified Communications system. It provides call control and signaling for voice, video, and other collaboration applications over IP networks. First released as Cisco CallManager, CUCM serves as the centralized software platform that enables enterprises to manage dial plans, endpoints, gateways, and related communications services across a converged network.

Architecture and deployment: CUCM runs as software on Cisco hardware platforms or as a supported virtualized instance. It operates in clusters that consist of a publisher and one or more subscribers. The publisher stores the primary configuration database, while subscribers handle call processing and services. Clusters can be deployed across sites to provide redundancy and disaster recovery. Endpoints include Cisco IP phones and softclients, with connectivity to the PSTN via gateways or SIP trunks.

Features and integrations: CUCM provides call routing, feature-rich telephony capabilities, and signaling support for SIP and legacy protocols (SCCP, H.323 in older versions). It integrates with other Cisco collaboration components and third-party applications for voicemail, messaging, presence, and conferencing. Common integrations include Cisco Unity Connection for voicemail, Cisco Jabber for clients, and Cisco Unified Contact Center Express for call center functionality. Administration and monitoring are performed through the CUCM Administration interface and RTMT.

Licensing and lifecycle: CUCM is typically licensed per user or device, with maintenance and software upgrades delivered as part of Cisco's software lifecycle. Upgrades are applied through the administration interfaces, with supported migration paths between major releases to preserve configuration and services.