Cisco Unified Communications Manager backup servers use which protocol to transfer files?

TFTP is used by CUCM to distribute firmware images and device configuration files to IP phones and other endpoints, not to transfer backup archives.

CUCM's Disaster Recovery System (DRS) requires an SFTP server as the remote backup destination for cluster data. SFTP provides an encrypted and authenticated file transfer channel, ensuring that backup archives are securely transmitted from the CUCM publisher and subscriber nodes to the configured storage device.

SSH provides a secure remote shell session but is not the file transfer protocol used by CUCM DRS to move backup data to a storage server.

NDMP is a network backup protocol used by enterprise storage systems and NAS devices but is not supported by or used in the CUCM Disaster Recovery System.