SS7 ISUP Messages

SS7 ISUP Messages and their parameters :

Please Note : F = Fixed, O = Optional, V = Variable Length

You can find detailed information about parameters here :

ISUP Parameters

ACM (Address Complete Message)

An Address Complete Message (ACM) is sent in the "backward" direction to indicate that the remote end of a trunk circuit has been reserved. The originating switch responds to an ACM message by connecting the calling party's line to the trunk to complete the voice circuit from the calling party to the called party. The terminating switch sends a ringing tone to the calling party's line.

Parameter Type Length (octet) Message type F 1Backward Call Indicators F 2Optional Backward Call Indicators O 3Call Reference O 7Cause Indicators O 4-?User to User Indicators O 3User to User Information O 3-131Access Transport O 3-?Generic Notification Indicator O 3Transmission Medium Used O 3Echo Control Information O 3Access Delivery Information O 3Redirection Number O 5-12Parameter Compatibility Information O 4-?Call Diversion Information O 3Network Specific Facility O 4-?Remote Operations O 3-?Service Activation O 3-?Redirection Number Restriction O 3End of Optional Parameters O 1

ANM (Answer Message)

When the called party answers, the destination switch terminates power ringing of the called line, removes audible ringing tone from the calling line and sends an Answer Message (ANM) to the originating switch. The originating switch initiates billing after verifying that the calling party's line is connected to the reserved trunk.

Parameter Type Length (octet) Message type F 1Backward Call Indicators O 4Optional Backward Call Indicators O 3Call Reference O 7User to User Indicators O 3User to User Information O 3-131Connected Number O 4-12Access Transport O 3-?

Generic Notification Indicator O 3Call History Information O 4Transmission Medium Used O 3Generic Number O 4-12Echo Control Information O 3Access Delivery Information O 3Redirection Number O 5-12Parameter Compatibility Information O 4-?Network Specific Facility O 4-?Remote Operations O 3-?Service Activation O 3-?Redirection Number Restriction O 3End of Optional Parameters O 1

Call Progress Message (CPG)

CPG is sent in either direction during the set-up or active phase of the call, indicating that an event, which is of significance, and should be relayed to the originating or terminating access, has occurred.

Parameter Type Length (octet) Message type F 1Event Information F 1Cause Indicators O 4-?Backward Call Indicators O 4Optional Backward Call Indicators O 3Call Reference O 7User to User Indicators O 3User to User Information O 3-131Connected Number O 4-12Access Transport O 3-?Generic Notification Indicator O 3Call Diversion Information O 3Transmission Medium Used O 3Access Delivery Information O 3Redirection Number O 5-12Parameter Compatibility Information O 4-?Network Specific Facility O 4-?Remote Operations O 3-?Service Activation O 3-?Redirection Number Restriction O 3End of Optional Parameters O 1

Circuit Group Response Message (CQR)

Sent in response to a Circuit/CIC Group Query message to indicate the state of all circuits/CICs in a particular range.

Parameter Type Length (octet) Message type F 1Range and Status V 2Circuit State Indicator V 3-33

Circuit Group Reset Acknowledgement Message (GRA)

GRA is sent in response to a Circuit/CIC Group Reset message indicating that the requested group of circuits/CICs has been reset. The message also indicates the maintenance blocking state of each circuit/CIC.

Parameter Type Length (octet) Message type F 1Range and Status V 3-34

Confusion Message (CFN)

CFN is sent in response to any message (other than a confusion message) if the node does not recognize the message or detects a part of the message as being unrecognized.

Parameter Type Length (octet) Message type F 1Cause Indicators V 4-20End of Optional Parameters O 1

Connect Message (CON)

CON is sent in the backward direction indicating that all the address signals required for routeing the call to the called party have been received and that the call has been answered.

Parameter Type Length (octet) Message type F 1Backward Call Indicators O 2Optional Backward Call Indicators O 3Call Reference O 7User to User Indicators O 3User to User Information O 3-131Connected Number O 4-12

Access Transport O 3-?Generic Notification Indicator O 3Call History Information O 3Transmission Medium Used O 3Generic Number O 4-12Echo Control Information O 3Access Delivery Information O 3Redirection Number O 5-12Parameter Compatibility Information O 4-?Network Specific Facility O 4-?Remote Operations O ?Service Activation O 3-?Redirection Number Restriction O 3End of Optional Parameters O 1

Continuity Message (COT)

COT is sent in the forward direction indicating whether or not there is continuity on the preceding circuit(s) as well as of the selected circuit to the following exchange, including verification of the communication path across the exchange with the specified degree of reliability.

Parameter Type Length (octet) Message type F 1Continiuty Indicators F 1

Facility Reject Message (FRJ)

FRJ is sent in response to a facility request message to indicate that the facility request has been rejected.

Parameter Type Length (octet) Message type F 1Facility Indicators F 1Cause Indicators V 4User to User Indicators O 3End of Optional Parameters O 1

Information Message (INF)

INF is sent to convey information in association with a call, which may have been requested in an information request message.

Parameter Type Length (octet) Message type F 1Information Indicators F 2Calling Party's Category O 3Calling Party Number O 5-12Call Reference O 7Connection Request O 7-9Parameter Compatibility Information O 4-?Network Specific Facility O 6-?End of Optional Parameters O 1

Information Request Message (INR)

INF is sent by a node to request information in association with a call.

Parameter Type Length (octet) Message type F 1Information Request Indicators F 2Call Reference O 7Parameter Compatibility Information O 4-?Network Specific Facility O 4-?End of Optional Parameters O 1

IAM (Initial Address Message)

An Initial Address Message (IAM) is sent in the "forward" direction by each switch needed to complete the circuit between the calling party and called party until the circuit connects to the destination switch. An IAM contains the called party number in the mandatory variable part and may contain the calling party name and number in the optional part.

Parameter Type Length (octet) Message type F 1Nature of Connection Indicators F 1Forward Call Indicators F 2Calling Party's Category F 1Transmission Medium Requirement F 1Called Party Number V 4-11Transit Network Selection O 4-?Call Reference O 7Calling Party Number O 4-12Optional Forward Call Indicators O 3Redirecting Number O 4-12Redirection Information O 3-4Closed User Group Interlock Code O 6

Connection Request O 7-9Origional Called Number O 4-12User to User Information O 3-131Access Transport O 3-?User Service Information O 4-13User to User Indicators O 3Generic Number O 5-13Propagation Delay Counter O 4User Service Information Prime O 4-13Network Specific Facility O 4-?Generic Digit O ?Originating ISC Point Code O 4User Service Information Prime O 7Remote Operations O ?Parameter Compatibility Information O 4-?Generic Notification O 3Service Activation O 3-?Generic Reference O 5-?MLPP Precedence O 8Transmission Medium Requirement Prime O 3Location Number O 5-12End of Optional Parameters O 1

REL (Release Message)

A Release Message (REL) is sent in either direction indicating that the circuit is being released due to the cause indicator specified. An REL is sent when either the calling or called party "hangs up" the call (cause = 16). An REL is also sent in the backward direction if the called party line is busy (cause = 17).

Parameter Type Length (octet) Message type F 1Cause Indicators V 3-?Redirection Information O 3-4Redirection Number O 5-12User to User Indicators O 3User to User Information O 3-131Access Transport O 3-?Access Delivery Information O 3Parameter Compatibility Information O 4-?Network Specific Facility O 4-?signalingPoint Code O 4Automatic Congestion Level O 4Redirection Number Restriction O 3End of Optional Parameters O 1

Release Complete Message

A Release Complete Message (RLC) is sent in the opposite direction of the REL to acknowledge the release of the remote end of a trunk circuit and end the billing cycle as appropriate.

Parameter Type Length (octet) Message type F 1Cause Indicators O 5-6End of Optional Parameters O 1

Subsequent Address Message (SAM)

SAM is sent in the forward direction following an initial address message, to convey additional called party number information.

Parameter Type Length (octet) Message type F 1Subsequent Number V 3-10End of Optional Parameters O 1

User to User Information Message (USR)

USR is used for the transport of user to user signaling independent of call control messages.

Parameter Type Length (octet) Message type F 1User to User Information V 2-130Access Transport O 3-?End of Optional Parameters O 1

Forward Transfer Message (FOT)

A message sent in the forward direction on semi automatic calls when the outgoing international exchange operator wants the help of an operator at the incoming international exchange. The message will normally serve to bring an assistance operator into the call if the call is automatically set up at the exchange.

Parameter Type Length (octet) Message type F 1Call Reference O 7

End of Optional Parameters O 1

Resume (RES), Suspend (SUS) Messages

RES is sent in either direction indicating that the calling or called party, after having been suspended, is reconnected.

SUS is sent in either direction indicating that the calling or called party has been temporarily disconnected.

Parameter Type Length (octet) Message type F 1Suspend, Resume Indicators F 1Call Reference O 7End of Optional Parameters O 1

Blocking (BLO) , Blocking Acknowledgement (BLA), Continuity Check Request (CCR) , Loop Back Acknowledgement (LPA), Overload (OLM), Reset Circuit (RSC), Unblocking

(UBL), Unblocking Acknowledgement (UBA), Unequipped Circuit Identification Code (UCIC)

Blocking (BLO) message sent only for maintenance purposes to the exchange at the other end of a circuit, to cause an engaged condition of that circuit for subsequent calls outgoing from that exchange. When a circuit is used in the bothway mode of operation, an exchange receiving the blocking message must be capable of accepting incoming calls on the concerned circuit unless it has also sent a blocking message. Under certain conditions, a blocking message is also a proper response to a reset circuit message.

Blocking Acknowledgement (BLA) message sent in response to a blocking message indicating that the circuit has been blocked.

Continuity Check Request (CCR) message sent by an exchange for a circuit on which a continuity check is to be performed, to the exchange at the other end of the circuit, requesting continuity checking equipment to be attached.

Loop Back Acknowledgement (LPA) message sent in the backward direction in response to a continuity check request message indicating that a loop (or transceiver in the case of a 2-wire circuit) has been connected.

Overload (OLM) message sent in the backward direction, on non?priority calls in response to an IAM, to invoke temporary trunk blocking of the circuit concerned when the exchange generating the message is subject to load control.

Reset Circuit (RSC) message sent to release a circuit/CIC when, due to memory mutilation or other causes, it is unknown whether for example, a Release or a Release Complete message is appropriate. If, at the receiving end, the circuit/CIC is remotely blocked, reception of this message should cause that condition to be removed.

Unblocking (UBL) message sent to the exchange at the other end of a circuit to cancel, in that exchange, the engaged condition of the circuit caused by a previously sent blocking or circuit group blocking message.

Unblocking Acknowledgement (UBA) message sent in response to an unblocking message indicating that the circuit has been unblocked.

Unequipped Circuit Identification Code (UCIC) message sent from one node to another when it receives a message on a circuit/CIC that is not provisioned for use.

Parameter Type Length (octet) Message type F 1

Circuit Group Blocking (CGB), Circuit Group Blocking Ack. (CGBA), Circuit Group Unblocking (CGU), Circuit Group Unblocking Ack. (CGUA) Messages

Circuit Group Blocking (CGB) message sent to the node to permit the switching equipment or maintenance system to remove from (and return to) traffic a group of circuits/CICs. A node receiving a Circuit/CIC Group Blocking message must be able to accept incoming calls on the group of blocked circuits/CICs unless it has also sent a Circuit/CIC Group Blocking message.

Circuit Group Blocking Acknowledgement (CGBA) message sent in response to a Circuit/CIC Group Blocking message to indicate that the requested group of circuits/CICs has been blocked.

Circuit Group Unblocking (CGU) message sent to the node to cause cancellation in a group of circuits/CICs of a blocked condition invoked earlier by a Circuit/CIC Group Blocking message.

Circuit Group Unblocking Acknowledgement (CGUA) message sent in response to a Circuit/CIC Group Unblocking message to indicate that the requested group of circuits/CICs has been unblocked.

Parameter Type Length (octet) Message type F 1Circuit group supervision message type indicators F 1Range and Status V 3-34

Circuit Group Reset (GRS), Circuit Group Query (CQM) Messages

Circuit Group Reset (GRS) message sent to release an identified group of circuits/CICs when, due to memory mutilation or other causes, it is unknown whether for example, a release or release complete message is appropriate for each of the circuits/CICs in the group. If at the receiving end a circuit/CIC is remotely blocked, reception of this message should cause that condition to be removed.

Circuit Group Query (CQM) message sent on a routine or demand basis to request the far-end node to give the state of all circuits/CICs in a particular range.

Parameter Type Length (octet) Message type F 1Range and Status V 2

Facility Accepted (FAA), Facility Request (FAR) Messages

Accepted (FAA) message sent in response to a facility request message indicating that the requested facility has been invoked.

Facility Request (FAR) message sent from a node to another node to request activation of a facility.

Parameter Type Length (octet) Message type F 1Facility Indicators F 1Call Reference O 7User to User Indicators O 3Connection Request O 9Parameter Compatibility Information O 4-?End of Optional Parameters O 1

Pass-along (PAM) Message

Pass-along (PAM) message that may be sent in either direction to transfer information between two signalingpoints along the same signalingpath as that used to establish a physical connection between those two points.

Parameter Type Length (octet) Message type F 1

User Part Test (UPT), User Part Available (UPA) Messages

User Part Test (UPT) message sent in either direction to test the status of a user part marked as unavailable for a signaling point.

User Part Available (UPA) message sent in either direction as a response to a user part test message, to indicate that the user part is available.

Parameter Type Length (octet) Message type F 1Parameter Compatibility Information O 4-?

End of Optional Parameters O 1

Facility (FAC) Message

Facility (FAC) message sent in either direction at any phase of the call to request an action at another node. The message is also used to carry the results, error or rejection of a previously requested action.

Parameter Type Length (octet) Message type F 1Service Activation O 3-?Remote Operations O ?Message Compatibility Information O 4Parameter Compatibility Information O 4-?End of Optional Parameters O 1

Network Resorce Management (NRM) Message

Network Resource Management (NRM) message sent in order to modify network resources associated with a certain call. The message is sent along an established path in any direction in any phase of the call.

Parameter Type Length (octet) Message type F 1Echo Control Information O 3Transmission Medium Used O 3Message Compatibility Information O 4Parameter Compatibility Information O 4-?End of Optional Parameters O 1

Identification Request (IDR) Message

Identification Request (IDR) message sent in the backward direction to request action regarding the malicious call identification supplementary service.

Parameter Type Length (octet) Message type F 1MCID Request Indicators O 3-?Message Compatibility Information O 4-?Parameter Compatibility Information O 4-?End of Optional Parameters O 1

Identification Response (IRS) Message

Identification Response (IRS) message sent in response to the identification request message.

Parameter Type Length (octet) Message type F 1MCID Response Indicators O 3-?Message Compatibility Information O 4-?Parameter Compatibility Information O 4-?Calling Party Number O 5-12Access Transport O 3-?Generic Number O 5-13End of Optional Parameters O 1

Segmentation (SGM) Message

Segmentation (SGM) message sent in either direction to convey an additional segment of an overlength message.

Parameter Type Length (octet) Message type F 1User to User Information O 3-131Message Compatibility Information O 4-5Generic Digit O ?Generic Notification O 3Access Transport O 3-?Generic Number O 5-13End of Optional Parameters O 1