In Cisco Unified Communications Manager, for which type of trunk is URI dialing available?

H.225 trunks in CUCM are gatekeeper-controlled trunks that leverage the H.225 call signaling protocol within the H.323 framework, and CUCM supports URI-based directory routing on this trunk type through gatekeeper URI resolution. The gatekeeper can resolve directory URIs and map them to IP endpoints, enabling URI dialing across the H.225 trunk. This makes H.225 the applicable trunk type in CUCM when URI dialing is required in an H.323 gatekeeper-managed environment.

SIP trunks natively use SIP URIs, but the question targets the specific CUCM trunk type classification where URI dialing is enabled through the H.225 gatekeeper-controlled trunk, not the SIP trunk.

QSIG is a supplementary services signaling protocol used over ISDN PRI for PBX interconnects and has no mechanism for URI-based dialing.

H.323 trunks in CUCM are non-gatekeeper-controlled trunks that use direct IP addressing for routing and do not support URI dialing in this context.