H.323 Supported Messages and Protocols

If an optional Gatekeeper is present in the network, H.225 defines the RAS (Registration, Admission, and Status) messages used to communicate with the gatekeeper. Below is a list of supported RAS messages.

ARQ (Admission Request)

A request from an endpoint to a gatekeeper for permission to participate in a call. The gatekeeper formulates its reply based on several factors, including the availability of bandwidth in the network.

ACF (Admission Confirm)

An positive response from a gatekeeper that authorizes the endpoint to participate in a call. The ACF contains an IP address of the terminating gateway/gatekeeper and enables the gateway sending the request to initiate call control.

ARJ (Admission Reject)

A message sent from the gatekeeper rejecting the ARQ message that initiates a call.

RRQ (Registration Request)

Message is sent to a gatekeeper by an endpoint to request that the endpoint be registered and become under the control of that gatekeeper. Registration requests are predefined in the systems administrative setup.

RCF (Registration Confirm)

A message sent from a gatekeeper to an endpoint in response to a RRQ. The message confirms registration into the gatekeeper.

RRJ (Registration Reject)

A message sent from the gatekeeper to an endpoint that rejects the RRQ message initially sent by the endpoint.

IRQ (Info Request)

This message is sent from a gatekeeper to request status information of its recipient endpoints.

IRR (Info Request Response)

This message is sent from an endpoint to a gatekeeper in response to an IRQ. This message is also sent from an endpoint to a gatekeeper if the gatekeeper requests periodic status updates. The IRR is used by gateways to inform the gatekeeper about the active calls.

IACK (Info Request Acknowledge)

Message sent from the gatekeeper which is in response to an IRQ message.

INAK (Info Request Neg Acknowledge)

Message sent from the gatekeeper which is in response to an IRQ message.

GRQ (Gatekeeper Request)

A message sent from an endpoint to a gatekeeper to "discover" gatekeepers willing to provide service.

GCF (Gatekeeper Confirm)

A response to a gatekeeper Request sent from the gatekeeper to the endpoint. The response indicates the transport address of the gatekeeper RAS channel.

GRJ (Gatekeeper Reject)

A response in regards to a GRQ from the gatekeeper to the endpoint indicating the gatekeeper rejected the endpoints request. This message is usually sent due to a gateway or gatekeeper configuration error.

DRQ (Disengage Request)

Message sent from the endpoint to the gatekeeper when the call ends. The Billing Information Token (contains the duration of the call) is embedded  within the message

DCF (Disengage Confirm)

Message sent from the gatekeeper to the endpoint in response to the Disengage Request message sent.

DRJ (Disengage Reject)

Message sent from the gatekeeper to the endpoint in response to the Disengage Request message sent. The gatekeeper is rejecting the Disengage Request message initially sent.

URJ (Unregistration Request)

Message is sent from the endpoint to the gatekeeper to cancel a registration between the endpoint and the gatekeeper

UCF (Unregistration Confirm)

Message is sent from gatekeeper to endpoint confirming the unregistration request.

URJ (Unregistration Reject)

Message sent from gatekeeper to endpoint indicating the endpoint was not pre-registered with the gatekeeper.

BRQ - Bandwidth Request

BCF - Bandwidth Confirm

BRJ - Bandwidth Reject

LRQ - Location Request

LCF - Location Confirm

LRJ - Location Reject

RIP -  Request in Progress

RAI - Resource Availability Indicator

RAC - Resource Availability Confirm