ACM (Address Complete Message)

Address Complete Message (ACM) is a message sent by a public switched telephone network (PSTN) to a calling party to indicate that a call is being connected to the called party. ACM is an important component of the call setup process in a PSTN and is used to signal the successful completion of a call setup attempt.

In this article, we will discuss in detail the various aspects of ACM, including its purpose, format, and usage.

Purpose of ACM

The primary purpose of the ACM message is to notify the calling party that the call setup attempt has been successful, and that the call is being connected to the called party. The ACM message is sent by the network after it has received an answer message (such as an Answer or Connect message) from the called party's network. The ACM message contains information about the call setup attempt, such as the reason for the call setup failure, if any, and the cause of the call release, if the call is subsequently released.

ACM messages are typically used in circuit-switched networks, where calls are set up using dedicated circuits between the calling and called parties. In such networks, the ACM message is an essential component of the call setup process, as it indicates to the calling party that the network has successfully set up the call and that the parties can now communicate with each other.

Format of ACM

The format of the ACM message is defined by the ITU-T Q.763 standard. The message consists of a header and one or more parameters. The header contains information about the message type, the length of the message, and other administrative information. The parameters contain information about the call setup attempt and its status.

The following is the format of the ACM message:javaCopy code

Header Message Type (MT) : ACM (0x08) Message Length (ML) : Total length of the message in octets, including the header Mandatory Fixed Length Parameters (MFLP) : Number of mandatory fixed length parameters in the message Mandatory Variable Length Parameters (MVLP) : Number of mandatory variable length parameters in the message Optional Parameters (OP) : Number of optional parameters in the message Parameters Mandatory Fixed Length Parameters Circuit Identification Code (CIC) : The circuit identification code for the circuit used for the call setup attempt Mandatory Variable Length Parameters Called Party Number (CDPN) : The phone number of the called party Cause Indicators (CI) : Information about the cause of the call setup attempt, such as the reason for failure or release Optional Parameters User-User Information (UUI) : Optional information provided by the calling party to the called party

Usage of ACM

The ACM message is used by the PSTN to indicate to the calling party that the call setup attempt has been successful and that the parties can now communicate with each other. The message is sent after the PSTN has received an answer message (such as an Answer or Connect message) from the called party's network.

When the calling party initiates a call, the PSTN sends a setup message to the called party's network to request the setup of a circuit for the call. The called party's network responds with an answer message, which can be an Answer or Connect message, indicating whether the call setup attempt was successful or not. If the call setup attempt is successful, the PSTN sends an ACM message to the calling party to indicate that the call is being connected to the called party.

If the call setup attempt fails, the PSTN sends a release message to the calling party, indicating the reason for the failure. The release message may contain information about the cause of the failure, such as a busy signal or a network error.

In addition to the above, the ACM message can also be used to convey additional information about the call setup attempt and its status. For example, the Cause Indicators parameter in the ACM message can provide information about the reason for the call setup failure or the cause of the call release.

The User-User Information parameter in the ACM message is optional and can be used to convey additional information from the calling party to the called party. This parameter can be used to provide additional context or instructions for the call, such as indicating that the call is urgent or providing a reference number for the call.

ACM messages are an important component of the call setup process in a PSTN. They provide critical information to the calling party about the status of the call setup attempt, and they enable the parties to communicate with each other once the call has been successfully set up.

Conclusion

In conclusion, Address Complete Message (ACM) is a message sent by a PSTN to a calling party to indicate that a call is being connected to the called party. ACM messages are an essential component of the call setup process in a PSTN, as they indicate to the calling party that the network has successfully set up the call and that the parties can now communicate with each other.

The ACM message format is defined by the ITU-T Q.763 standard and consists of a header and one or more parameters. The parameters contain information about the call setup attempt and its status, such as the reason for the call setup failure or the cause of the call release.

ACM messages are an important part of the PSTN and enable efficient communication between parties. As communication technology continues to evolve, new messaging systems may replace the PSTN, but the concepts and principles of messages like the ACM will continue to be important.