Which service parameter must be configured in Cisco Unified Communications Manager to enable SIP PUBLISH on a SIP trunk as the mechanism for presence interaction with Cisco Unified Presence?

The 'IM and Presence publish trunk' parameter explicitly marks a SIP trunk as the channel over which CUCM sends SIP PUBLISH messages containing phone presence information - such as on-hook or off-hook status - to the Cisco Unified Presence server. Without this parameter set, CUCM will not use the trunk for presence publication. This is the only parameter that directly enables the SIP PUBLISH mechanism for this integration.

Route class trunk is used for routing class of service classification on trunks and has no function related to SIP PUBLISH or presence signaling.

Processing on QSIG trunk pertains to QSIG protocol handling on PRI trunks, which is unrelated to SIP-based presence publication.

Fail call over SIP trunk is a redundancy and failover parameter that controls call rerouting behavior, not presence publication.