12 Extensions within the present document

24.5813GPPMission Critical Video (MCVideo) media plane controlProtocol specificationRelease 18TS

12.1 Session description types defined within the present document

12.1.1 General

This clause contains definitions for SDP parameters that are specific to SDP usage with MCVideo and therefore are not described in an RFC.

12.1.2 SDP "fmtp" attribute for MCVideo

12.1.2.1 General

This clause defines the structure and syntax of the SDP "fmtp" attribute, when used to negotiate an MCVideo media plane control channel. The MCVideo media plane control channel, and the protocols used on the control channel, is described in the present specification.

12.1.2.2 Semantics

In an SDP offer and answer, the "mc_queueing" fmtp attribute is used to indicate support of the Transmission Request message queueing mechanism, as defined in the present specification.

In an SDP offer, the "mc_priority" fmtp attribute indicates (using an integer value between ‘1’ and ‘255’) the maximum transmission priority that the offerer requests to be used with Transmission Request messages sent by the offerer. In an SDP answer, the attribute parameter indicates the maximum priority level that the answerer has granted to the offerer. The value must be equal or less than the value provided in the associated SDP offer.

NOTE 1: If the "mc_priority" fmtp attribute is not used within an SDP offer or answer, a default priority value is assumed.

In an SDP offer, the "mc_reception_priority" fmtp attribute indicates (using an integer value between ‘1’ and ‘255’) the maximum reception priority that the offerer requests to be used with Reception Request messages sent by the offerer. In an SDP answer, the attribute parameter indicates the maximum reception priority level that the answerer has granted to the offerer. The value must be equal or less than the value provided in the associated SDP offer.

NOTE 2: If the "mc_reception_priority" fmtp attribute is not used within an SDP offer or answer, a default reception priority value is assumed.

In an SDP offer, the "mc_granted" fmtp attribute parameter indicates that the offerer supports the procedure where the answerer indicates, using the fmtp attribute in the associated SDP answer, that the permission to transmit has been granted to the offerer.

NOTE 3: When the "mc_granted" fmtp attribute is used in an SDP offer, it does not indicate an actual request for the media transmission. The SDP "mc_implicit_request" fmtp attribute can be used to request the media transmission. In an SDP answer, the attribute indicates that the permission to Transmission has been granted to the offerer.

NOTE 4: Once the offerer has been granted the permission to Transmission, the offerer can perform media transmission until it receives a Transmission Revoked message, or until the offerer itself ends the media transmission by sending a Transmission end request message, as described in the present specification.

In an SDP offer, the "mc_implicit_request" fmtp attribute indicates that the offerer implicitly requests for media transmission (without the need to send a Transmission Request message). In an SDP answer, the attribute parameter indicates that the answerer has accepted the implicit Transmission Request. Once the answerer grants the permission to Transmission to the offerer, the answerer will send a Transmission Granted message.

NOTE 5: The usage of the "mc_implicit_request" fmtp attribute in an SDP answer does not mean that the answerer has granted the permission to Transmission to the offerer, only that the answerer has accepted the implicit Transmission Request.

12.1.2.3 Syntax

Table 12.1.2.3-1: SDP "fmtp" attribute for the MCVideo media plane control channel

fmtp-attr-mpcp = "a=fmtp:" "MCVideo" SP attr-param-list

attr-param-list = attr-param *(COLON attr-param)

attr-param = mc_queueing / mc_priority / mc_reception_priority / mc_granted / mc_implicit_request

mc_queueing = "mc_queueing"

mc_priority = "mc_priority=" 1*2(DIGIT)

mc_reception_priority = "mc_reception_priority=" 1*2(DIGIT)

mc_granted = "mc_granted"

mc_implicit_request = "mc_implicit_request"

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