Signaling System No.7 Protocol Architecture And Sevices part 67

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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

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Nội dung Text: Signaling System No.7 Protocol Architecture And Sevices part 67

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 FULL MESSAGE MESSAGE/CODE NAME PURPOSE CR Connection Sent by SCCP to another SCCP peer to Request request a setup of a logical signaling 00000001 connection between them so that data transfer can take place in a connection- orientated fashion. CC Connection Sent in response to a CR message to Confirm indicate that the node has performed 00000010 the setup of the requested logical signaling connection. CREF Connection Sent by the destination or an Refused intermediate SCCP node in response to 00000011 a CR message to indicate a refusal to set up a logical signaling connection. AK (NE) Data May be sent when using protocol class Acknowledgment 3 to control the window flow. 00001000 DT1 Data Form 1 Sent by either end of a logical signaling connection to pass SCCP 00000110 user data transparently between two SCCP nodes. DT1 is only used in protocol class 2. DT2 (NE) Data Form 2 Sent by either end of a logical signaling connection to pass SCCP 00000111 user data transparently between two SCCP nodes. DT2 is only used in
protocol class 3. ED (NE) Expedited Data Performs the same function as the DT2 message, but includes the capability to 00001011 bypass the flow control mechanism and is, therefore, only used in protocol class 3. EA (NE) Expedited Data Used to acknowledge an ED message. Acknowledgment Each ED message must be 00001100 acknowledged before another is sent. XUDT Extended Unitdata Used by SCCP to transmit data with optional parameters, using 00010001 connectionless classes 0 and 1. XUDTS Extended Unitdata Sent back in response to a XUDT Service message if the XUDT message cannot 00010010 be delivered to its destination. Only used when the optional field in XUDT is set to "return on error." Protocol class indeterminate due to absence of protocol class parameter. IT Inactivity Test May be sent periodically by either end of a logical signaling connection to 0 0 01 0 0 0 0 make sure the logical signaling connection is active and to audit the consistency of connection data at both ends. Used in connection-orientated classes 2 and 3. LUDT Long Unitdata Used by SCCP to transmit data with optional parameters, using 00010011 connectionless 0 and 1. If ATM is the underlying network, it allows sending of Network Service Data Unit (NSDU) sizes up to 3952 octets without segmentation. LUDTS Long Unitdata Sent back in response to a LUDT Service message if the LUDT message cannot 00010100 be delivered to its destination. Only
used when the optional field in LUDT is set to "return on error." Protocol class indeterminate due to absence of protocol class parameter. ERR Protocol Data Unit Sent on detection of any protocol Error errors. Used during the data transfer 00001111 phase in connection-orientated classes 2 and 3. RLC Release Complete Sent in response to the Released (RLSD) message to indicate that the 00000101 RLSD message was received and that the necessary procedures have been performed. Used during connection release phase in connection-orientated classes 2 and 3. RLSD Released Sent to indicate that the sending SCCP wishes to release a logical signaling 00000100 connection and that the associated resources have been brought into the disconnect pending condition. Also indicates that the receiving node should release the logical signaling connection and its associated resources. Used during connection release phase in connection-orientated classes 2 and 3. RSC (NE) Reset Confirm Sent in response to a Reset Request (RSR) message to indicate that RSR 00001110 has been received and that the necessary procedure has been performed. Used during the data transfer phase in connection-orientated class 3. RSR (NE) Reset Request Sent to indicate that the sending SCCP wishes to initiate a reset procedure (re-
00001101 initialization of sequence numbers) with the receiving SCCP. Used during the data transfer phase in protocol class 3. SBR (M)(A) Subsystem Backup Optional message sent before rerouting Routing traffic to the backup subsystem. 11111101 Provides more connectivity information so the end node can determine the traffic mix received for a subsystem. SNR (M)(A) Subsystem Normal Optional message sent prior to Routing rerouting traffic to the primary 111111110 subsystem, to the backup of the subsystem that is now allowed. Allows the end node to update the traffic mix information that the subsystem is receiving. SRT (A) Subsystem Routing Optional message sent to verify the Status Test routing status of a subsystem marked 11111111 as under backup routing. SSA (M) Subsystem Used by SCCP subsystem management Allowed (SCMG) to inform SCMG at 00000001 concerned destinations that a formerly prohibited subsystem (such as VLR/HLR) is now available, or that a previously unavailable SCCP is now available. As a result, the node receiving the SSA updates its translation tables. SSP (M) Subsystem Used by SCCP subsystem management Prohibited (SCMG) to inform SCMG at 00000010 concerned destinations that a subsystem (such as VLR/HLR) has failed. The receiving end of an SSP message updates its translation tables; as a result, traffic could be re-routed to
a backup subsystem, if available. SST (M) Subsystem Status Used by SCCP subsystem management Test (SCMG) to verify the status of a 00000011 subsystem marked prohibited or the status of an SCCP marked unavailable. The receiving node checks the status of the named subsystem and, if the subsystem is allowed, sends an SSA message in response. If the subsystem is prohibited, no reply is sent. SOR (M) Subsystem Out-of- Used by SCCP subsystem management Service Request (SCMG) to allow subsystems to go 00000100 out-of-service without degrading performance of the network. SOG (M) Subsystem Out-of- Used by SCCP subsystem management service-grant (SCMG) in response to a Subsystem 00000101 Out-of-Service Request (SOR) message to the requesting SCCP if both the requested SCCP and the backup of the affected subsystem agree to the request. SSC (M)(I) SCCP/subsystem- Sent when an SCCP node experiences congested congestion. 00000010 UDT Unitdata Used by SCCP to transmit data, using connectionless classes 0 and 1. 00001001 UDTS Unitdata Service Sent in response to a UDT message if the UDT message cannot be delivered 00001010 to its destination. Only used when the optional field in UDT is set to "return on error." Used in connectionless protocol classes 0 and 1. KEY: (A)—Messages supported in ANSI SCCP Messages not supported in ETSI SCCP [].cellular network, does not seem place to define them as reader should
know them only [2]. (I)—Messages supported in ITU-T SCCP only [60]. (NE)—Messages not supported in ETSI SCCP [10]. (M)—SCCP subsystem management (SCMG). These are transmitted within the data parameter a UDT, XUDT or LUDT message.