Appendix C. SCCP Messages (ANSI/ETSI/ITU-T) The table in this appendix summarizes Signaling Connection Control Part (SCCP) messages and the purpose of each. For an introduction to SCCP, refer | Appendix C. SCCP Messages ANSI ETSI ITU-T The table in this appendix summarizes Signaling Connection Control Part SCCP messages and the purpose of each. For an introduction to SCCP refer to Chapter 9 Signaling Connection Control Part SCCP . Table C-1. SCCP Messages MESSAGE CODE FULL MESSAGE NAME PURPOSE CR 0 0 0 0 0 0 0 1 Connection Request Sent by SCCP to another SCCP peer to request a setup of a logical signaling connection between them so that data transfer can take place in a connection-orientated fashion. CC 0 0 0 0 0 0 1 0 Connection Confirm Sent in response to a CR message to indicate that the node has performed the setup of the requested logical signaling connection. CREF 0 0 0 0 0 0 1 1 Connection Refused Sent by the destination or an intermediate SCCP node in response to a CR message to indicate a refusal to set up a logical signaling connection. AK NE 0 0 0 0 1 0 0 0 Data Acknowledgment May be sent when using protocol class 3 to control the window flow. DT1 0 0 0 0 0 1 1 0 Data Form 1 Sent by either end of a logical signaling connection to pass SCCP user data transparently between two SCCP nodes. DT1 is only used in protocol class 2. DT2 NE 0 0 0 0 0 1 1 1 Data Form 2 Sent by either end of a logical signaling connection to pass SCCP user data transparently between two SCCP nodes. DT2 is only used in protocol class 3. ED NE 0 0 0 0 1 0 1 1 Expedited Data Performs the same function as the DT2 message but includes the capability to bypass the flow control mechanism and is therefore only used in protocol class 3. EA NE 0 0 0 0 1 1 0 0 Expedited Data Acknowledgment Used to acknowledge an ED message. Each ED message must be acknowledged before another is sent. XUDT 0 0 0 1 0 0 0 1 Extended Unitdata Used by SCCP to transmit data with optional parameters using connectionless classes 0 and 1. XUDTS 0 0 0 1 0 0 1 0 Extended Unitdata Service Sent back in response to a XUDT message if the XUDT message cannot be delivered to its destination. Only used when the .
