18 Forced Playout Constraints

26.2373GPPIP Multimedia Subsystem (IMS) based Packet Switch Streaming (PSS) and Multimedia Broadcast/Multicast Service (MBMS) User ServiceProtocolsRelease 17TS

18.1 General Description

Figure 39: Forced Playout Constraints policy delivery and execution

NOTE 1: This sequence is simplified and does not e.g. show session progress messages and the ACK message from the UE in response to the reception of 200 OK.

NOTE 2: SIP messages between PSS adapter and SCF go through the IM CN Subsystem even if not indicated on the sequences.

18.2 Procedures at the UE

The UE shall perform PSS session initialization as per procedure defined in sub-clause 8.2.3.2 and playback control as defined in sub-clause 8.2.4.2.

When receiving a SIP INFO message, within a PSS service, the UE shall identify it contains forced playout constraints policy by checking whether the content-type in the message header. Following that, the UE shall then extract the policy from the SIP message body and store it.

During the playback of the PSS service, the UE should not issue any RTSP request message when it is not supported as indicated in the policy document.

18.3 Procedures at the IM CN Subsystem

The IM CN Subsystem handles the SIP dialog as defined in 3GPP TS 23.228 [6].

18.4 Procedures at the SCF

The SCF shall perform PSS session initialization as per procedure defined in sub-clause 8.2.3.4.

To support Forced Playout Constraints, the following shall apply:

– The SCF shall acquire information about the playout constraints policy from the content provider. This information shall include the start and end time of controlled content and a list of RTSP operations that are to be controlled. The SCF then uses this information to generate the Policy. When a user requests to consume the content, the SCF shall check the user’s service rights and based upon this shall decide whether to issue the policy or not.

– Once receiving a SIP 200 OK response from PSS Adapter, the SCF shall check whether it has a forced playout constraints policy applicable to the selected content. If yes, the SCF shall save the response and :

– Issue a SIP INFO message contains the policy to the PSS Adapter selected for the session. Upon receiving a SIP 200 OK, the SCF shall forward the saved response to UE;

– Then the SCF shall further issue a SIP INFO message contains the policy to the UE.

The SIP INFO message SHALL include a XML body to describing the forced playout constraints policy. The XML body shall conform to the XML schema defined in Annex T of TISPAN [24]. The parameters shall be included as follows:

ContentID: the identifier for a content that SHALL be controlled by the forced playout constraints policy.

StartTime: the start time that the forced playout constraints SHALL be enforced.

EndTime: the end time that the forced playout constraints SHALL be enforced.

RTSPOperation: the RTSP operations that are not permitted.

18.5 Procedures at the PSS Adapter

The PSS Adapter shall perform PSS session initialization as per procedure defined in sub-clause 8.2.3.5 and playback control as defined in sub-clause 8.2.4.3.

To support Forced Playout Constraints, when receiving a SIP INFO message ,within a PSS service, the PSS Adapter shall identify it contains forced playout constraints policy by checking whether the content-type in the message header is "application/3gpp-ims-pss-mbms-forced-playout+xml". Following that, the PSS Adapter shall extract the forced playout constraints policy from the SIP message body and store it for enforcement against the content in the concerned session.

If the PSS Adapter received any forced playout constraints policy document during session setup, the PSS Adapter shall save the policy. Upon receiving a RTSP request from UE during the playback, the PSS Adapter shall check whether the requested operation is permitted as per the policy. If the requested operation is forbidden by the policy, the PSS Adapter shall disable the request and respond with a RTSP 405(Method Not Allowed) message.