O.2A Usage of SDP

24.2293GPPIP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP)Release 18Stage 3TS

O.2A.0 General

Not applicable.

O.2A.1 Impact on SDP offer / answer of activation or modification of IP-CAN bearer context for media by the network

If, due to the activation of an IP-CAN bearer context from the network the related SDP media description needs to be changed the UE shall update the related SDP information by sending a new SDP offer within a SIP request, which is sent over the existing SIP dialog,

If the UE receives a modification request from the network for an IP-CAN bearer context that is used for one or more media streams in an ongoing SIP session, the UE shall:

1) if, due to the modification of the IP-CAN bearer context, the related SDP media description need to be changed, update the related SDP information by sending a new SDP offer within a SIP request, that is sent over the existing SIP dialog, and respond to the IP-CAN bearer context modification request.

NOTE: The UE can decide to indicate additional media streams as well as additional or different codecs in the SDP offer than those used in the already ongoing session.

O.2A.2 Handling of SDP at the terminating UE when originating UE has resources available and IP-CAN performs network-initiated resource reservation for terminating UE

If the UE receives an SDP offer where the SDP offer includes all media streams for which the originating side indicated its local preconditions as met, if the precondition mechanism is supported by the terminating UE and the IP-CAN performs network-initiated resource reservation for the terminating UE and the available resources are not sufficient for the received offer the terminating UE shall indicate its local preconditions and provide the SDP answer to the originating side without waiting for resource reservation.

NOTE: If the resource reservation is controlled by the network, the resource reservation request is initiated by the network after the P-CSCF has authorised the respective IP flows and provided the QoS requirements over the Rx interface to the PCRF as described in 3GPP TS 29.214 [13D].

O.2A.3 Emergency service

No additional procedures defined.