H.323 Signaling

H.323 operates using three main protocols, discussed at length in Chapter 4:

• Registration, Admission, and Status (RAS) for interaction with H.323 gatekeepers
• H.225 for the call signaling phase of a call
• H.245 for the media control phase of a call

RAS Messaging Details

The RAS protocol supported by CallManager includes specific message types and information elements. The RAS message support provided by CallManager is the H.225 version 2 protocol. Tables C-1 through C-7 describe the specific fields. The tables are arranged alphabetically by message type. Table C-1 shows the fields that an H.323 entity uses to discover the gatekeeper. CallManager does not currently support RAS discovery messages, but they are included here for completeness.

Table C-1. H.225 RAS Terminal and Gateway Discovery Message Details: User-User Information Element (UUIE) Fields

Message	Field Name	Comments
GRQ (Gatekeeper Request) to GK (Gatekeeper)	requestSeqNumber	Not used in CallManager 4.1
	protocolIdentifier
	nonStandardData
	rasAddress
	endpointType
	gatekeeperIdentifier
	callServices
	endpointAlias
	alternateEndpoints
	tokens
	cryptoTokens
	authenticationCapability
	algorithmsOIDs
	integrity
	integrityCheckValue
GCF (Gatekeeper Confirmation) from GK	requestSeqNumber	Allowed, but ignored when received
	protocolIdentifier
	nonStandardData
	gatekeeperIdentifier
	rasAddress
	alternateGatekeeper
	authenticationMode
	tokens
	cryptoTokens
	algorithmsOIDs
	integrity
	integrityCheckValue
GRJ (Gatekeeper Reject) from GK	requestSeqNumber	Allowed, but ignored when received
	protocolIdentifier
	nonStandardData
	gatekeeperIdentifier
	rejectReason
	altGKInfo
	Tokens
	cryptoTokens
	integrityCheckValue

CallManager uses registration messages to register with the gatekeeper that the manual or automatic discovery process identifies. CallManager attempts to register with the gatekeeper and, if not successful, retries the registration at configurable intervals.

Table C-2 shows the fields that CallManager uses to register with the gatekeeper.

Table C-2. H.225 RAS Registration Message Details: UUIE Fields

Message	Field Name	Comments
RRQ (Registration Request) to GK	requestSeqNumber	Unique sequence number that is incremented for each new request
	protocolIdentifier	Set to v2
	nonStandardData	Not used
	discoveryComplete	Set to false
	callSignalAddress	Set to the IP and port of the call signaling address
	rasAddress	Set to the IP and port of the RAS signaling address
	terminalType	Set to indicate terminal or gateway device
	terminalAlias	No alias set
	gatekeeperIdentifier	Gatekeeper ID set
	alternateEndpoints	Set to transport addresses of alternate CallManager nodes
	timeTolive	Set to configuration value; defaults to 60
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	keepAlive	Set to true if this is a refresh registration
	endpointIdentifier	Endpoint ID set
	willSupplyUUIEs	Defaults to false
RCF (Registration Confirmation) from GK	requestSeqNumber	Unique sequence number
	protocolIdentifier	CallManager does not screen this field
	nonStandardData	Not used
	callSignalAddress	CallManager sends H.225 signaling to this address
	terminalAlias	Not used
	gatekeeperIdentifier	Identifies the H.323 zone
	endpointIdentifier	Endpoint identifier
	alternateGatekeeper	Defines gatekeepers to contact if registering gatekeeper is unavailable
	timeTolive	CallManager periodically reregisters according to this timer
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	willRespondToIRR	Ignored
	pregrantedARQ	Not used
RRJ (Registration Reject) from GK	requestSeqNumber	Unique sequence number
	protocolIdentifier	Not screened
	nonStandardData	Not used
	rejectReason	Reject reason
	gatekeeperIdentifier	Indicates the zone of the rejecting gatekeeper
	altGKInfo	Indicates an alternate gatekeeper with which to register
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported

CallManager uses unregistration messages to unregister from the gatekeeper when a gatekeeper registered device is stopped. Table C-3 shows the fields that CallManager uses to unregister from the gatekeeper.

Table C-3. H.225 RAS Unregistration Message Details: UUIE Fields

Message	Field Name	Comments
URQ (Unregister Request) to GK	requestSeqNumber	Unique sequence number that is incremented for each new request
	protocolIdentifier	Not screened
	callSignalAddress	Set to the IP and port of the call signaling address
	endpointAlias	Not set
	nonStandardData	Not used
	endpointIdentifier	Indicates the identifier of the unregistering request
	alternateEndpoints	Not used
	gatekeeperIdentifier	Not set
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	reason	CallManager sets no reason and ignores the reason when receiving a URQ
UCF (Unregister Confirm) from GK	requestSeqNumber	Allowed, but ignored when received
	nonStandardData
	tokens
	cryptoTokens
	integrityCheckValue
URJ (Unregister Reject) from GK	requestSeqNumber	Allowed, but ignored when received
	rejectReason
	nonStandardData
	altGKInfo
	tokens
	cryptoTokens
	integrityCheckValue

CallManager uses call admission control to discover routes to other CallManager clusters and gateways and to determine whether enough bandwidth exists for CallManager to place or receive a call.

Table C-4 shows the fields that CallManager uses to exchange call admission control messages with the gatekeeper.

Table C-4. H.225 RAS Admission Message Details: UUIE Fields

Message	Field Name	Comments
ARQ (Admission Request) to GK	requestSeqNumber	Unique sequence number that is incremented for each new request
	callType	Set to point to point
	callModel	Not set
	endpointIdentifier	Set to endpoint ID
	destinationInfo	Up to 16 E.164 addresses
	destCallSignalAddress	IP address, if set by CallManager
	destExtraCallInfo	Not set
	srcInfo	If present, a list of up to 16 E.164 addresses
	srcCallSignalAddress	Set to the IP and port of the call signaling address
	bandwidth	Requested bandwidth to be used
	callReferenceValue	Set to call reference value for this call
	nonStandardData	Not used
	callServices	Set to None
	conferenceId	Unique conference identifier
	activeMC	Set to false for no multipoint controller (MC)
	answeredCall	Set to true if call is incoming, false on outgoing
	canMapAlias	Set to true
	callIdentifier	Unique call identifier
	srcAlternatives	Set to None
	gatekeeperIdentifier	Not set
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	transportQOS	Not supported
	willSupplyUUIEs	Defaults to false
ACF (Admission Confirm) from GK	requestSeqNumber	Unique sequence number
	bandWidth	Not used
	callModel	CallManager always acts as if the response is direct
	destCallSignalAddress	Uses the IP address to specify the call signaling address; used if configured for anonymous device; ignored otherwise
	irrFrequency	Used to specify the Information Request Response (IRR) frequency in seconds while on the call
	nonStandardData	Not used
	destinationInfo	Not used
	destExtraCallInfo	Not used
	destinationType	Not used
	remoteExtensionAddress	Not used
	alternateEndpoints	Transport address of associated H.323 trunks
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	transportQOS	Not supported
	willRespondToIRR	Not used
	uuiesRequested	Not used
ARJ (Admission Reject) from GK	requestSeqNumber	Unique sequence number
	rejectReason	Used only for ARJ trace display
	nonStandardData	Not used
	altGKInfo	If provided, CallManager contacts the alternate gatekeeper
	tokens	Not supported
	cryptoTokens	Not supported
	callSignalAddress	Not used
	integrityCheckValue	Not supported

CallManager does not use bandwidth control messages by default. Bandwidth control messages are used if you set the service parameter to enable bandwidth control. Table C-5 shows the bandwidth message fields.

Table C-5. H.225 RAS Bandwidth Message Details: UUIE Fields

Message	Field Name	Comments
BRQ (Bandwidth Request) from GK	requestSeqNumber	CallManager returns a BRJ (Bandwidth Reject)
	endpointIdentifier
	conferenceID
	callReferenceValue
	callType
	bandWidth
	nonStandardData
	callIdentifier
	gatekeeperIdentifier
	tokens
	cryptoTokens
	integrityCheckValue
	answeredCall
BRQ (Bandwidth Request) to GK	requestSeqNumber	Unique sequence number
	endpointIdentifier	Endpoint identifier
	conferenceID	Unique conference identifier
	callReferenceValue	Call reference value
	callType	Point to point
	bandWidth	New bandwidth
	nonStandardData	Not used
	callIdentifier	Unique call identifier
	gatekeeperIdentifier	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	answeredCall	True on terminating side
BCF (Bandwidth Confirm) from GK	requestSeqNumber	Unique sequence number
	bandWidth	Bandwidth granted
	nonStandardData	Not used
	tokens	Not used
	cryptoTokens	Not used
	integrityCheckValue	Not used
BRJ (Bandwidth Reject) from GK	requestSeqNumber	Unique sequence number
	rejectReason	Reason bandwidth change was disallowed
	allowedBandWidth	Amount of bandwidth allowed
	nonStandardData	Not used
	altGKInfo	ID of alternate gatekeeper
	tokens	Not used
	cryptoTokens	Not used
	integrityCheckValue	Not used

Gatekeepers use disengage messages to force a call to be dropped. CallManager uses disengage messages to indicate that an endpoint is being dropped.

Table C-6 shows the fields that CallManager uses to exchange disengage messages with the gatekeeper.

Table C-6. H.225 RAS Disengage Message Details: UUIE Fields

Message	Field Name	Comments
DRQ (Disengage Request) to or from GK	requestSeqNumber	Unique sequence number
	endpointIdentifier	Endpoint identifier
	conferenceID	Unique conference identifier
	callReferenceValue	Call reference value
	disengageReason	If sent, set to reason; if received, used to set the release complete reason
	nonStandardData	Not used
	callIdentifier	Unique call identifier
	gatekeeperIdentifier	Not used
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	answeredCall	Supported
DCF (Disengage Confirm) to or from GK	requestSeqNumber	Unique sequence number
	nonStandardData	Not used
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
DRJ (Disengage Reject) from GK	requestSeqNumber	Unique sequence number
	rejectReason	CallManager ignores
	nonStandardData	Not used
	altGKInfo	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported

The gatekeeper sends Information Request (IRQ) messages to request status information. CallManager responds to information request messages from the gatekeeper with Information Request Response (IRR) messages, but CallManager does not send unsolicited IRQ messages to the gatekeeper. IRR messages are sent at the intervals specified by the irrFrequency field in the ACF message.

Table C-7 shows the fields that CallManager uses to exchange information request messages with the gatekeeper.

Table C-7. H.225 RAS Information Request Message Details: UUIE Fields

Message	Field Name	Comments
IRQ (Information Request) from GK	requestSeqNumber	Unique sequence number
	callReferenceValue	Call reference value
	nonStandardData	Not used
	replyAddress	Not used
	callIdentifier	Not used
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	uuiesRequested	Not used
IRR (Information Request Response) to GK	nonStandardData	Not used
	requestSeqNumber	Unique sequence number
	endpointType	Set to terminal or gateway
	endpointIdentifier	Endpoint identifier
	rasAddress	Set to the IP address and port of the RAS signaling address
	callSignalAddress	Not present
	endpointAlias	Not present
	perCallInfo	See the following perCall fields
	perCallInfo.nonStandardData	Not used
	perCallInfo.callReferenceValue	Call reference value
	perCallInfo.conferenceId	Unique conference ID
	perCallInfo.originator	Set to false
	perCallInfo.audio	Not set
	perCallInfo.video	Not set
	perCallInfo.data	Not set
IRR (Information Request Response) to GK	perCallInfo.h245	Set to false
	perCallInfo.callSignaling	Not present
	perCallInfo.callType	Point to point
	perCallInfo.bandwidth	Set to 1280 for a G.711 call; 480 for a G.729 call
	perCallInfo.callModel	Set to direct
	perCallInfo.callIdentifier	Call ID
	perCallInfo.tokens	Not supported
	perCallInfo.cryptoTokens	Not supported
	perCallInfo.substituteConfIDs	Not supported
	perCallInfo.pdu	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	integrityCheckValue	Not supported
	needResponse	Not supported
IACK (Information Request Acknowledgement) from GK	requestSeqNumber	Allowed, but ignored when received
	nonStandardData
	tokens
	cryptoTokens
	integrityCheckValue
INAK (Information Request Negative Acknowledgement) from GK	requestSeqNumber	Allowed, but ignored when received
	nonStandardData
	nakReason
	altGKInfo
	tokens
	cryptoTokens
	integrityCheckValue

 

H.225 Messaging Details

H.323 messages, including the call signaling messages, follow the ITU-T Q.931 recommendation as specified in H.323. In H.323, the user-user information element (UUIE) conveys the H.323-related information. The H.323 user information protocol data unit (PDU) is ASN.1-encoded. The ASN.1 is encoded using the basic aligned variant of the packed encoding rules as specified in X.691. The ASN.1 structure begins with H323-UserInformation.

H.225 is the call signaling protocol that is supported in the H.323 protocol umbrella. H.225 includes the call signaling messages and the RAS messages. This section covers the specific details of the H.225 call signaling messages.

Table C-8 lists each H.225 message and provides the specific UUIE fields of the H.225 call signaling messages that CallManager exchanges with an H.323 gateway or CallManager H.323 trunk (gateway in table).

Table C-8. H.225 Call Signaling Message Details: UUIE Fields

Message	Field Name	Comments
Alerting from gateway	protocolIdentifier	Assumes version 2 (v2); only v2 fields are processed
	destinationInfo	Used
	h245Address	Used if present
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
Alerting to gateway	protocolIdentifier	Set to v2
	destinationInfo	Endpoint type terminal
	h245Address	If present at alerting, contains the IP address and port of the CallManager H.245 transport address
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
CallProceeding from gateway	protocolIdentifier	Assumes v2; only v2 fields are processed
	destinationInfo	Used
	h245Address	Used if present
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
CallProceeding to gateway	protocolIdentifier	Set to v2
	destinationInfo	Endpoint type terminal
	h245Address	If present at CallProceeding, contains the IP address and port of the CallManager H.245 transport address
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
Connect from gateway	protocolDiscriminator	Assumes v2; only v2 fields are processed
	h245Address	Used if present; required if not present in previous message
	destinationInfo	Used
	conferenceId	Required
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
Connect to gateway	protocolDiscriminator	Set to v2
	h245Address	Contains the IP address and port of the CallManager H.245 transport address
	destinationInfo	Endpoint type terminal
	conferenceId	Unique conference identifier
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
Facility from and to gateway	protocolDiscriminator	Set to v2
	alternativeAddress	Not used
	alternativeAliasAddress	Not used
	conferenceID	Not used
	reason	Used
	callIdentifier	Unique call identifier
	destExtraCallInfo	Not used
	remoteExtensionAddress	Not used
	tokens	Not used
	cryptoTokens	Not used
	conferences	Not used
	h245Address	Not used
UserInformation from gateway	protocolIdentifier	Assumes v2; only v2 fields are processed
	callIdentifier	Not used
UserInformation to gateway	protocolIdentifier	Set to v2
	callIdentifier	Unique call identifier
Progress from gateway	protocolIdentifier	Assumes v2; only v2 fields are processed
	destinationInfo	Not used
	h245Address	Used if present; required if not present in previous message
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
Progress to gateway	protocolIdentifier	Set to v2
	destinationInfo	Endpoint type terminal
	h245Address	Contains the IP address and port of the CallManager H.245 transport address
	callIdentifier	Unique call identifier
	h245SecurityMode	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
ReleaseComplete from gateway	protocolIdentifier	Assumes v2; only v2 fields are processed
	reason	Reason for disconnect
	callIdentifier	Unique call identifier
ReleaseComplete to gateway	protocolIdentifier	Set to v2
	reason	Reason for disconnect
	callIdentifier	Unique call identifier
Setup from gateway	protocolIdentifier	Assumes v2; only v2 fields are processed
	h245Address	Contains the IP address and port of the CallManager H.245 transport address
	sourceInfo	Not used
	sourceAddress	Source address if provided
	destinationAddress	Not used; E.164 address is in the Q.931 called party number IE (information element)
	destCallSignalAddress	Not used
	destExtraCallInfo	Not used
	destExtraCRV	Not used
	activeMC	Used
	conferenceId	Unique conference identifier
	conferenceGoal	Used
	callServices	Not used
	callType	Used
	sourceCallSignalAddress	Used
	remoteExtensionAddress	Not used
	callIdentifier	Unique call identifier
	h245SecurityCapability	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
	mediaWaitForConnect	Used if present; defaults to false if not present
	canOverlapSend	Not used
Setup to gateway	protocolIdentifier	Set to v2
	h245Address	Contains the IP address and port of the CallManager H.245 transport address
	sourceInfo	Endpoint type terminal
	sourceAddress	Source address as E.164 address, H.323 alias, or both
	destinationIAddress	E.164 address present here and also included in the Q.931 called party number IE (information element)
	destinationCallSignalAdd ress	Not used
	destExtraCallInfo	Not used
	destExtraCRV	Not used
	activeMC	Used
	conferenceId	Unique conference identifier
	conferenceGoal	Set to create
	callServices	Not used
	callType	Point to point
	sourceCallSignalAddress	Used
	remoteExtensionAddress	Not used
	callIdentifier	Unique call identifier
	h245SecurityCapability	Not supported
	tokens	Not supported
	cryptoTokens	Not supported
	fastStart	Supported
	mediaWaitForConnect	Set to true
	canOverlapSend	Set to false