• Request – This type of primitive is invoked by a higher lower to the layer below and represents a service request at the service access point.
• Confirm – This type of primitive is supplied in response to a previous Request, from the lower layer to the higher layer, and provides the status of the completed service request.
• Indication – This type of primitive is supplied by a lower layer to the higher layer and is an asynchronous notification of receipt of an incoming request from a remote device.
• Response – This type of primitive is supplied by a higher layer to the lower layer and supplies the status of a previous Indication for transmittal to a remote device.
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