5.2.2 Message flows and types for online charging

32.2813GPPAnnouncement serviceCharging managementRelease 17Telecommunication managementTS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The following figures show the Reserve Units transactions that are required between the IMS-GWF/AS and the OCS for session-related IMS procedures when the Announcement service is invoked.

The SIP messages and Charging Data transactions associated with these charging scenarios are shown primarily for general information and to illustrate the charging triggers. They are not intended to be exhaustive and they depend on the Reserve Units Request triggers configured by the operator.

All of the scenarios depict originating sessions only.

Scenario 1: Pre-quota announcement with successful session establishment

Figure 5.2.2.1 shows the Reserve Units transactions that are required in the IMS-GWF/AS during a SIP session establishment for which a pre-quota announcement is requested with successful session establishment.

Figure 5.2.2.1: Message sequence chart for pre-quota announcement with successful session establishment

1) An initial SIP Invite Request is received in the S-CSCF. This request is forwarded to the IMS-GWF/AS.

2) The IMS-GWF/AS sends a Reserve Units Request[Initial] to the OCS requesting service units. The online Credit-Control session is initiated.

3) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result and requests an announcement to be played to the calling party immediately. Announcement information may indicate whether or not the granted quota for the IMS session shall be used for playing the announcement.

3a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

3b) The MRFP plays the announcement to the calling party.

3c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

4) The IMS-GWF/AS and S-CSCF forward the initial SIP INVITE.

5) A final response is received in the IMS-GWF/AS.

6) If the trigger is active, the SIP 200 OK answer triggers a Reserve Units Request[Update] in the IMS-GWF/AS in order to update the Credit-Control session. New service units are requested in a Multiple Unit Operation. Also the used service units (if any) are reported in the Multiple Unit Operation. If the indication in step 3 is to use the granted quota then the quota usage allocated for playing the announcement shall be reported by the IMS-GWF/AS to the OCS in the used service units.

7) The OCS sends the Reserve Units Response to acknowledge the Reserve Units Request. New service units are granted in a Multiple Unit Operation.

8) The final answer is forwarded.

Scenario 2: Pre-quota announcement with session termination

Figure 5.2.2.2 shows the Reserve Units transactions that are required in the IMS-GWF/AS during a SIP session establishment for which a pre-quota announcement is requested with the termination of the session.

Figure 5.2.2.2: Message sequence chart for pre-quota announcement with session termination

1) An initial SIP Invite Request is received in the S-CSCF. This request is forwarded to the IMS-GWF/AS.

2) The IMS-GWF/AS sends a Reserve Units Request[Initial] to the OCS requesting service units. The online Credit-Control session is initiated.

3) The OCS rejects the session in the Reserve Units Response with an unsuccessful Operation Result and requests an announcement to be played to the calling party immediately. No quota is used during the announcement playback when the SIP session is to be terminated.

3a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

3b) The MRFP plays the announcement to the calling party.

3c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

4) The IMS-GWF/AS and S-CSCF releases the session with a SIP BYE that is forwarded by the S-CSCF towards the calling party. The message sequence shown here assumes that the announcement playback established a SIP dialog with the calling party in Step 3a. For other variations of SIP session termination for use when announcement playback utilized signalling for early media, see Annex B of TS 32.260 [20].

5) A final response is forward by the S-CSCF to the IMS-GWF/AS.

Scenario 3: Mid-quota announcement during IMS session

Figure 5.2.2.3 shows the Reserve Units transactions that are required in the IMS-GWF/AS for a mid-quota announcement during an established IMS session, followed by session continuation.

Figure 5.2.2.3: Message sequence chart for mid-quota announcement during IMS session

1) During an ongoing SIP session, a charging trigger encountered for an update as per table 5.3.1.1 in TS 32.260 [20]. The IMS-GWF/AS sends a Reserve Units Request[Update] to the OCS requesting service units.

2) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result and requests an announcement to be played to the calling party prior to quota exhaustion. Announcement information may indicate whether or not the granted quota for the IMS session shall be used for playing the announcement. The announcement is indicated as to be played to a specified duration before the end of the quota is reached.

2a) When the timing conditions are met for the requeted announcement, the IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

2b) The MRFP plays the announcement to the calling party.

2c) When the announcement is complete, the IMS-GWF/AS re-connects the called party, disconnecting the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

Scenario 4: Post-quota announcement with IMS session termination

Figure 5.2.2.4 shows the Reserve Units transactions that are required in the IMS-GWF/AS for a post-quota announcement which is initiated at final quota exhaust.

Figure 5.2.2.4: Message sequence chart for post-quota announcement with IMS session termination

2) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result, a final unit indication and a request for an announcement to be played when the quota is exhausted. Granted quota shall not be used for an announcement playback at final quota exhaust.

3) When end of quota is reached, the IMS-GWF/AS initiates session termination to the called party by sending a SIP BYE message which is forwarded by the S-CSCF.

4) The final answer to the SIP BYE message is forwarded by the S-CSCF to the IMS-GWF/AS ending the SIP dialog with the called party. The IMS-GWF/AS does not wait for this response before continuing the message sequence.

5a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

5b) The MRFP plays the announcement to the calling party.

5c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

6) The IMS-GWF/AS initiates session termination to the calling party by sending a SIP BYE message which is forwarded by the S-CSCF.

7) The IMS-GWF/AS sends a Reserve Units Request[Terminate] reporting the used service units in a Multiple Unit Operation.

8) The OCS sends a Reserve Units Response. The online Credit-Control session is terminated.

9) The final answer to the SIP BYE message is forwarded by the S-CSCF to the IMS-GWF/AS ending the SIP dialog.

Scenario 5: Combined pre- and post-quota announcements with IMS session termination

Figure 5.2.2.5 shows the Reserve Units transactions that are required in the IMS-GWF/AS during a SIP session establishment for which a pre-quota announcement is requested at IMS session initiation along with a post-quota announcement to be played at final quota exhaust.

Figure 5.2.2.5: Message sequence chart for combined pre- and post-quota announcement with IMS session termination

1) An initial SIP Invite Request is received in the S-CSCF. This request is forwarded to the IMS-GWF/AS.

2) The IMS-GWF/AS sends a Reserve Units Request[Initial] to the OCS requesting service units. The online Credit-Control session is initiated.

3) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result and a final unit indication. The OCS requests an announcement to be played immediately and an announcement to be played at the final end of quota. Only the announcement information for the immediate announcement may indicate to use granted quota for the announcement playback.

3a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

3b) The MRFP plays the announcement to the calling party.

3c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

4) The IMS-GWF/AS and S-CSCF forward the initial SIP INVITE.

5) A final response is received in the IMS-GWF/AS.

6) The final answer is forwarded.

7) When end of quota is reached, the IMS-GWF/AS initiates session termination to the called party by sending a SIP BYE message which is forwarded by the S-CSCF.

8) The final answer to the SIP BYE message is forwarded by the S-CSCF to the IMS-GWF/AS ending the SIP dialog with the called party. The IMS-GWF/AS does not wait for this response before continuing the message sequence.

9a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

9b) The MRFP plays the announcement to the calling party.

9c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

10) The IMS-GWF/AS initiates session termination to the calling party by sending a SIP BYE message which is forwarded by the S-CSCF.

11) The IMS-GWF/AS sends a Reserve Units Request[Terminate] reporting the used service units in a Multiple Unit Operation. If the indication in step 3 is to use the granted quota for the announcement playback then the quota usage for playing the announcement shall be reported by the IMS-GWF/AS to the OCS in the used service units. This is applicable only for an announcement initiated prior to end of granted quota.

12) The OCS sends a Reserve Units Response. The online Credit-Control session is terminated.

13) The final answer to the SIP BYE message is forwarded by the S-CSCF to the IMS-GWF/AS ending the SIP dialog.

Scenario 6: Combined mid- and post-quota announcements with IMS session termination

Figure 5.2.2.6 shows the Reserve Units transactions that are required in the IMS-GWF/AS for a mid-quota announcement prior to final quota exhaust. An example would be to play a low balance warning tone to the calling party before the end of the call and then play a terminating announcement reminding the user to top up the account.

Figure 5.2.2.6: Message sequence chart for combined mid- and post-quota announcements with IMS session termination

2) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result and a final unit indication. The OCS requests an announcement to be played a specified number of seconds prior to end of quota and an announcement to be played at the final end of quota. Only the announcement information for the announcement prior to end of quota may indicate to use granted quota for the announcement playback.

2a) When the time prior to end of quota is reached, the IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

2b) The MRFP plays the announcement to the calling party.

2c) When the announcement is complete, the IMS-GWF/AS re-connects the called party, disconnecting the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

3) When end of quota is reached, the IMS-GWF/AS initiates session termination to the called party by sending a SIP BYE message which is forwarded by the S-CSCF.

5a) The IMS-GWF/AS establishes a SIP session between the calling party and an MRFC/MRFP for the requested announcement as per TS 24.628 [244] and TS 24.229 [204].

5b) The MRFP plays the announcement to the calling party.

5c) When the announcement is complete, the IMS-GWF/AS disconnects the SIP session with the MRFC/MRFP as per TS 24.628 [244] and TS 24.229 [204].

6) The IMS-GWF/AS initiates session termination to the calling party by sending a SIP BYE message which is forwarded by the S-CSCF.

7) The IMS-GWF/AS sends a Reserve Units Request[Terminate] reporting the used service units in a Multiple Unit Operation. If the indication in step 2 is to use the granted quota then the quota usage for playing the announcement shall be reported by the IMS-GWF/AS to the OCS in the used service units. This is applicable only for an announcement initiated prior to end of granted quota.

8) The OCS sends a Reserve Units Response. The online Credit-Control session is terminated.

9) The final answer to the SIP BYE message is forwarded by the S-CSCF to the IMS-GWF/AS ending the SIP dialog.

Scenario 7: Announcement handling subsequent to a Re-Auth-Request

Figure 5.2.2.7: Message sequence chart for of announcement handling subsequent to Re-Auth-Request message

2) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result and requests an announcement to be played to the calling party. Announcement information may indicate whether or not the granted quota for the IMS session shall be used for playing the announcement. A timing indicator is provided that can indicate the announcement be played immediately or delayed to a specified number of seconds before the end of the quota is reached.

3) As a result of an external event (e.g. recharge activity), the OCS decides that announcement needs to be cancelled.

4) The OCS sends a Re-Auth-Request to the IMS-GWF/AS requesting to perform new Reserve Units Request.

5) The IMS-GWF/AS sends a Re-Auth-Answer response to the OCS.

6) The IMS-GWF/AS sends a Reserve Units Request[Update] to the OCS requesting service units.

7) The OCS grants units in a Multiple Unit Operation of the Reserve Units Response with a successful Operation Result (with or without request for announcement). This cancels any pending announcement related to the previous granted quota.