In an H.323 call that is not interworked, meaning that both the caller and the callee are using the H.323 protocol, the Expressway acts as an H.323 gatekeeper and routes the following signaling protocols through itself:

Q.931: This is the call signaling protocol that is used to establish, maintain, and terminate calls between any two H.323 entities. Q.931 messages are exchanged over a TCP connection between the endpoints and the Expressway. The Expressway can perform address translation, admission control, and call routing based on the Q.931 messages.

RAS: This is the registration, admission, and status protocol that is used between an H.323 endpoint and the Expressway to provide services such as endpoint registration, address resolution, bandwidth management, and zone management. RAS messages are exchanged over a UDP connection between the endpoints and the Expressway. The Expressway can accept or reject registration requests, allocate bandwidth, and monitor the status of the endpoints based on the RAS messages.

H.245: This is the control protocol for multimedia communication that is used to negotiate the capabilities, open and close logical channels, and exchange control and indication signals for audio, video, and data streams. H.245 messages are exchanged over a TCP connection between the endpoints and the Expressway. The Expressway can modify or enforce the capabilities, allocate ports, and relay the media control signals based on the H.245 messages.

The other protocols, such as RTP, RTCP, and H.254, are not routed through the Expressway in an H.323 call that is not interworked. RTP and RTCP are the protocols for sending or receiving multimedia information (voice, video, or text) between the endpoints. H.254 is not a valid protocol name, but it might be a typo for H.264, which is a video coding standard that defines how video streams are compressed and decompressed. These protocols are exchanged directly between the endpoints over UDP connections, without involving the Expressway. References := Cisco Expressway Administrator Guide (X14.0) - About H.323Cisco Expressway Basic Configuration Deployment Guide (X14.0) - H.323 Call Flow [Cisco Expressway Administrator Guide (X14.0) - Configuring H.323]