Content for TS 23.334 Word version: 18.1.0

1… 4… 5… 5.11… 5.12… 5.14… 5.18… 5.19… 5.20… 5.21… 6… 6.1.6… 6.1.11… 6.2… 6.2.10… 6.2.10.3.1.2 6.2.10.3.2 6.2.10.4… 6.2.10.4.3… 6.2.10.5 6.2.10.6… 6.2.10A… 6.2.13… 6.2.14… 6.2.14.3 6.2.14.4… 6.2.15… 6.2.17… 6.2.17.3… 6.2.17.5… 6.2.18… 6.2.20 6.2.21… 6.2.22… 6.2.22.3… 6.2.22.3.2 6.2.23 6.2.24 6.2.25 7 8… 8.3 8.4 8.5… 8.23…

6 IMS-ALG to IMS-AGW Procedures p. 94

6.1 Non-Call Related Procedures p. 94

6.1.1 General p. 94

The non-call related procedures are based on corresponding procedures of TS 23.205 where the IMS-ALG takes the place of the MSC server and the IMS-AGW takes the place of the MGW.

6.1.2 IMS-AGW Unavailable p. 94

The IMS-ALG server recognises that the IMS-AGW is unavailable in the following 4 cases:

The signalling connection is unavailable

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.2.1: Signalling connection failure

Figure 6.1.2.1: Signalling connection failure
(⇒ copy of original 3GPP image)

The IMS-AGW indicates the failure or the maintenance locking condition to all connected IMS-ALG servers

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.2.2: IMS-AGW indicates the Failure/Maintenance locking

Figure 6.1.2.2: IMS-AGW indicates the Failure/Maintenance locking
(⇒ copy of original 3GPP image)

The failure or maintenance locking indication indicates that the IMS-AGW is locked for new calls or will soon go out of service and that no new connections should be established using this IMS-AGW. The IMS-AGW can choose between the "graceful" and the "forced" method. In the graceful method the connections are cleared when the corresponding calls are disconnected. In the forced method all connection are cleared immediately.

The IMS-ALG recognises that the IMS-AGW is not functioning correctly, e.g. because there is no reply on periodic sending of Audits. The periodic sending of Audits by IMS-ALG should go on.

In all of the above cases the IMS-ALG shall prevent the usage of the IMS-AGW until the IMS-AGW has recovered or the communication with the IMS-AGW is restored.

6.1.3 IMS-AGW Available p. 95

The IMS-ALG discovers that the IMS-AGW is available when it receives an IMS-AGW Communication Up message or an IMS-AGW Restoration message. If the IMS-ALG does not wish to sustain an association with the IMS-AGW, the response sent to the IMS-AGW may indicate an alternative IMS-ALG signalling address, in which case the IMS-AGW shall not consider itself registered and should preferably attempt to re-register with this alternative IMS-ALG before any further alternate IMS-ALGs. Otherwise, the response shall not indicate any alternative IMS-ALG signalling address.

When the IMS-ALG discovers that the IMS-AGW is available the following shall occur:

Signalling recovery

The IMS-AGW indicates to all connected IMS-ALGs that the signalling connection is restored.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.3.1: Communication goes up

Figure 6.1.3.1: Communication goes up
(⇒ copy of original 3GPP image)

IMS-AGW restoration/maintenance unlocking indication.

The IMS-AGW indicates to all connected IMS-ALGs that normal operation has resumed.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.3.2: IMS-AGW indicates recovery from a failure/or maintenance unlocking

Figure 6.1.3.2: IMS-AGW indicates recovery from a failure/or maintenance unlocking
(⇒ copy of original 3GPP image)

The IMS-ALG recognises that the IMS-AGW is now functioning correctly, e.g. because there is a reply on periodic sending of Audits.

After this the IMS-ALG can use the IMS-AGW.

If none of 1, 2, and 3 happens the IMS-ALG server can initiate the IMS-ALG Ordered Re-register procedure.

6.1.4 IMS-AGW Recovery p. 96

If the IMS-AGW recovers from a failure, is maintenance unlocked, or it has been restarted, it registers to its known IMS-ALGs using the IMS-AGW Restoration procedure or the IMS-AGW Registration procedure. The IMS-AGW can indicate whether the Service has been restored or whether it has restarted with a cold or warm boot. If the IMS-ALG does not wish to sustain an association with the IMS-AGW, the response sent to the IMS-AGW may indicate an alternative IMS-ALG signalling address, in which case the IMS-AGW shall not consider itself registered and should preferably attempt to re-register with this alternative IMS-ALG before any further alternate IMS-ALGs. Otherwise, the response shall not indicate any alternative IMS-ALG signalling address.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.4.1: IMS-AGW Restoration

Figure 6.1.4.1: IMS-AGW Restoration
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.4.2: IMS-AGW Registration

Figure 6.1.4.2: IMS-AGW Registration
(⇒ copy of original 3GPP image)

After the recovery the IMS-ALG can use the IMS-AGW.

6.1.5 IMS-ALG Recovery p. 96

6.1.5.1 General p. 96

If an IMS-AGW-unavailable condition is provoked by a failure/recovery action, the IMS-ALG recovery sequence will, from an information flow point of view, look like IMS-AGW unavailable and then IMS-AGW available. If an IMS-AGW-unavailable condition is not provoked, the IMS-ALG recovery sequence will look like IMS-AGW available.

After the information flow, the terminations affected by the recovery action are released.

6.1.5.2 IMS-ALG Restoration p. 97

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.1.5.2.1: IMS-ALG Restoration

Figure 6.1.5.2.1: IMS-ALG Restoration
(⇒ copy of original 3GPP image)

After the recovery action is complete and it is possible to signal to the IMS-AGW the IMS-ALG starts a timer Tw. If recovery indications are not received (IMS-AGW Communication Up or IMS-AGW Restoration) from the IMS-AGW during Tw an Audit is sent. If the IMS-ALG receives a recovery indication or IMS-AGW communication up indication, it shall acknowledge the indication before the IMS-ALG Restoration may be sent or the release procedure is initiated.