8.1.7   Fast connect procedure
H.323 endpoints may establish media channels in a call using either the procedures defined in Recommendation H.245 or the "Fast Connect" procedure described in this subclause. The Fast Connect procedure allows the endpoints to establish a basic point-to-point call with as few as one round-trip message exchange, enabling immediate media stream delivery upon call connection.
The calling endpoint initiates the Fast Connect procedure by sending a Setup message containing the fastStart element to the called endpoint. The fastStart element consists of a sequence of OpenLogicalChannel structures describing media channels which the calling endpoint proposes to send and receive, including all of the parameters necessary to immediately open and begin transferring media on the channels. Details of the content and usage of the fastStart element are discussed below.

OpenLogicalChannel    ::=SEQUENCE
{
    forwardLogicalChannelNumber    LogicalChannelNumber,

    forwardLogicalChannelParameters    SEQUENCE
    {
        portNumber    INTEGER (0..65535) OPTIONAL,
        dataType    DataType,
        multiplexParameters    CHOICE
        {
            h222LogicalChannelParameters    H222LogicalChannelParameters,
            h223LogicalChannelParameters    H223LogicalChannelParameters,
            v76LogicalChannelParameters    V76LogicalChannelParameters,
            ...,
            h2250LogicalChannelParameters    H2250LogicalChannelParameters,
            none    NULL  -- for use with Separate Stack when
                  -- multiplexParameters are not required
                  -- or appropriate

        },
        ...,
        forwardLogicalChannelDependency    LogicalChannelNumber OPTIONAL,
            -- also used to refer to the primary logical channel when using video redundancy coding
        replacementFor    LogicalChannelNumber OPTIONAL

    },

DataType        ::=CHOICE
{
    nonStandard    NonStandardParameter,
    nullData    NULL,
    videoData    VideoCapability,    
    audioData    AudioCapability,
    data        DataApplicationCapability,
    encryptionData    EncryptionMode,
    ...,
    h235Control    NonStandardParameter,
    h235Media    H235Media,
    multiplexedStream    MultiplexedStreamParameter
}

B.2.2.1 Capability Table
A TerminalCapabilitySet may contain zero or more CapabilityTableEntrys. At the start, no table entries are defined. When a CapabilityTableEntry is received, it replaces the previously received CapabilityTableEntry with the same CapabilityTableEntryNumber. A CapabilityTableEntry without a Capability may be used to remove the previously received CapabilityTableEntry with the same CapabilityTableEntryNumber.

B.2.2.2    Capability Descriptors
CapabilityDescriptors are used to indicate a terminal's capability to transmit and receive. Each CapabilityDescriptor provides an independent statement about the terminal's capabilities.

B.2.2.3    Capability
The choices receiveVideoCapability, receiveAudioCapability, receiveDataApplicationCapability, receiveUserInputCapability and receiveMultiplexedStreamCapability indicate the capability to receive according to the respective VideoCapability, AudioCapability, DataApplicationCapability, UserInputCapability and MultiplexedStreamCapability.
The choices transmitVideoCapability, transmitAudioCapability, transmitDataApplicationCapability, transmitUserInputCapability and transmitMultiplexedStreamCapability indicate the capability to transmit according to the respective VideoCapability, AudioCapability, DataApplicationCapability UserInputCapability and MultiplexedStreamCapability.
The choices receiveAndTransmitVideoCapability, receiveAndTransmitAudioCapability, receiveAndTransmitDataApplicationCapability, receiveAndTransmitUserInputCapability and receiveAndTransmitMultiplexedStreamCapability indicate the capability to receive and transmit symmetrically according to the respective VideoCapability, AudioCapability, DataApplicationCapability and UserInputCapability and MultiplexedStreamCapability. These code points may be useful for indicating that the receive and transmit capabilities are not independent

Capability        ::=CHOICE
{
    nonStandard    NonStandardParameter,

    receiveVideoCapability    VideoCapability,
    transmitVideoCapability    VideoCapability,
    receiveAndTransmitVideoCapability    VideoCapability,

    receiveAudioCapability    AudioCapability,
    transmitAudioCapability    AudioCapability,
    receiveAndTransmitAudioCapability    AudioCapability,

    receiveDataApplicationCapability    DataApplicationCapability,
    transmitDataApplicationCapability    DataApplicationCapability,
    receiveAndTransmitDataApplicationCapability    DataApplicationCapability,

    h233EncryptionTransmitCapability    BOOLEAN,
    h233EncryptionReceiveCapability    SEQUENCE
    {
        h233IVResponseTime    INTEGER (0..255),    -- units milliseconds    
        ...
    },
    ...,
    conferenceCapability    ConferenceCapability,
    h235SecurityCapability    H235SecurityCapability,
    maxPendingReplacementFor    INTEGER (0..255),
    receiveUserInputCapability    UserInputCapability,
    transmitUserInputCapability    UserInputCapability,
    receiveAndTransmitUserInputCapability    UserInputCapability,

    genericControlCapability    GenericCapability,
    receiveMultiplexedStreamCapability    MultiplexedStreamCapability,
    transmitMultiplexedStreamCapability    MultiplexedStreamCapability,
    receiveAndTransmitMultiplexedStreamCapability    MultiplexedStreamCapability,
    receiveRTPAudioTelephonyEventCapability    AudioTelephonyEventCapability,
    receiveRTPAudioToneCapability    AudioToneCapability
}

8.1.7.2    Switching to H.245 procedures
After establishment of a call using the Fast Connect procedure, either endpoint may determine that it is necessary to invoke call features that require the use of H.245 procedures. Either endpoint may initiate the use of H.245 procedures at any point during the call using tunneling as described in 8.2.1 (if h245Tunneling remains enabled). An H.323 Version 4 or higher entity that uses Fast Connect in a call shall use H.245 tunneling when an H.245 Control Channel is required and shall always set the h245Tunneling field to TRUE. The process for switching to a separate H.245 connection is described in 8.2.3 and may be used by Version 3 or older entities or by newer H.323 entities when communicating with Version 3 or older entities for the purpose of maintaining backward compatibility.
When a call is established using the Fast Connect procedure, both endpoints shall keep the Q.931 Call Signalling Channel open until either the call is terminated or, for compatibility with older endpoints, until a separate H.245 connection is established.
When H.245 procedures are activated, all mandatory procedures of H.245 that normally occur upon initiation of an H.245 connection shall be completed prior to initiation of any additional H.245 procedures. The media channels that were established in the Fast Connect procedure are "inherited" as though they had been opened using normal H.245 openLogicalChannel and openLogicalChannelAck procedures. In order for such "inheritance" to succeed, media sessions opened during the Fast Connect procedure shall use only well-known sessionID values defined in Recommendation H.245.
.......SKIP......
However, an endpoint may exchange the terminalCapabilitySet message and the masterSlaveDetermination message in the Setup message as described in section 8.2.4. Such an exchange constitutes the opening of the H.245 Control Channel, but does not preclude either endpoint from proceeding with Fast Connect.

If en bloc receiving is used, the SETUP message shall contain all the information required by the
called user to process the call. In this case, the SETUP message may contain the Sending complete
information element.

When the called endpoint desires to proceed with the Fast Connect procedure, it sends a Q.931 message (Call Proceeding, Progress, Alerting, or Connect) containing a fastStart element selecting from amongst the OpenLogicalChannel proposals offered by the calling endpoint. The calling endpoint shall process each of these messages until it determines that Fast Connect is accepted or refused. Although the calling endpoint may receive the fastStart element in a Facility message sent by a Gatekeeper, the called endpoint shall not use the Facility message to send fastStart. Channels thus accepted are considered opened as though the usual H.245 openLogicalChannel and openLogicalChannelAck procedure had been followed. The called endpoint shall not include a fastStart element in any Q.931 message sent after the Connect message and shall not include fastStart in any Q.931 message unless the Setup message contained a fastStart element.