Event ACRs Generated for Unsuccessful Session Attempts

When any of the following responses are received in response to a SIP Invite, an Event ACR message is created to indicate there has been an unsuccessful session attempt:

• 4xx Request Failure Code — this code is used when the SIP transaction is terminated due to an IMS node receiving a 4xx error response.
• 5xx Server Failure Code — this code is used when the SIP transaction is terminated due to an IMS node receiving a 5xx error response.
• 6xx Global Failure Code — this code is used when the SIP transaction is terminated due to an IMS node receiving a 6xx error response.

This example call flow shows how a 5xx server failure results in the sending of an Event ACR.

Call Flow Example Showing Event ACR Generation Due to 5xx Server Failure

The following call flow example shows two session agents. The first session agent replies with 503, which results in an Event ACR with cause code 503. The second session agent replies with 200OK that causes the sending of a Start ACR. The generate-start parameter is OK.

Call Flow Example Showing Sending of an Event and Start ACR

This example call flow illustrates the same call flow when generate-start are equal to Invite. In this case, Start, Interim and Stop ACRs are sent. The generate-start parameter is OK.

Call Flow Example Showing Generation of Event ACRs Due to 5xx Server Failures

This example call flow shows how a session is created and a Start ACR is sent but then a 5xx server failure occurs that results in sending an Interim ACR. The generate-start parameter is Invite.

Call Flow Example Showing Sending of Start and Interim ACRs

This example call flow shows how the SD rejects a call before a session is created. When the enhanced-cdr option is not set, an Event ACR is then sent.

Call Flow Example Showing Unsuccessful Session Creation and Sending of a Event ACR