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Content for  TS 24.380  Word version:  17.4.0

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1  ScopeWord‑p. 17

The present document specifies the media plane control protocols and interactions with the media needed to support Mission Critical Push To Talk (MCPTT).
The present document specifies protocol for using pre-established session to setup calls, floor control and managing MBMS subchannels over MBMS bearers on-network and off-network protocols for floor control.
Mission critical communication services are services that require preferential handling compared to normal telecommunication services, e.g. in support of police or fire brigade. Floor control provides a mechanism for managing the right to transmit at a point in time during an MCPTT call.
The MCPTT service and its associated media plane control protocols can be used for public safety applications and also for general commercial applications (e.g., utility companies and railways).
The present document is applicable to User Equipment (UE) supporting the floor participant functionality, setting up calls using pre-established SIP sessions and using MBMS bearers for group communication and to floor control servers supporting these functions in the MCPTT system.
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2  ReferencesWord‑p. 17

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 24.379: "Mission Critical Push To Talk (MCPTT) call control Protocol specification".
[3]
RFC 3550:  "RTP: A Transport Protocol for Real-Time Applications".
[4]
TS 24.483: "Mission Critical Services (MCS) Management Object (MO)".
[5]
TS 23.379: "Functional architecture and information flows to support mission critical communication services; Stage 2".
[6]
TS 29.468: "Group Communication System Enablers for LTE (GCSE_LTE); MB2 Reference Point; Stage 3".
[7]
RFC 5761:  "Multiplexing RTP Data and Control Packets on a Single Port".
[8]
RFC 3711:  "The Secure Real-time Protocol (SRTP)".
[9]
TS 25.446: "MBMS synchronization protocol (SYNC)".
[10]
TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)".
[11]
TS 24.008: "Mobile radio interface layer 3 specification; Core Network protocols; Stage 3".
[12]
TS 24.481: "Mission Critical Services (MCS) group management Protocol specification".
[13]
TS 24.484: "Mission Critical Services (MCS) configuration management protocol specification".
[14]
Void.
[15]
RFC 3830:  "MIKEY: Multimedia Internet KEYing".
[16]
RFC 3711:  "The Secure Real-time Transport Protocol (SRTP)".
[17]
RFC 6509:  "MIKEY-SAKKE: Sakai-Kashar Key Encryption in Multimedia Internet KEYing (MIKEY)".
[18]
TS 33.180: "Security of the mission critical service".
[19]
TS 23.032: "Universal Geographical Area Description (GAD)".
[20]
RFC 5795:  "The Robust Header Compression (ROHC) Framework".
[21]
RFC 3095:  "RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed".
[22]
RFC 5225:  "RObust Header Compression Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP-Lite".
[23]
TS 23.280: "Common functional architecture to support mission critical services; Stage 2".
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3  Definitions and abbreviationsWord‑p. 18

3.1  DefinitionsWord‑p. 18

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term or definition defined in the present document takes precedence over the definition of the same term or definition, if any, in TR 21.905.
Active floor request queue:
The floor request queue used by the floor control server to queue received Floor Request messages.
Candidate arbitrator:
The queued floor participant in off-network to whom the floor was granted. Once the candidate arbitrator responds to the floor grant, it becomes the current arbitrator.
Controlling MCPTT function:
The MCPTT server performing a controlling role.
Conversation:
A number of media bursts exchanged between participants in a group call session.
Current arbitrator:
The floor participant in off-network currently arbitrating the floor.
Effective priority:
The priority decision determined by the floor control server based on multiple input parameters like floor priority, participant type, type of call etc. of the current floor request and of the current participant to which floor is granted if any and the local policy.
MBMS bearer:
The service provided by the EPS to deliver the same IP datagrams to multiple receivers in a designated location.
MBMS subchannel:
A logical channel which uses resources of an activated and announced MBMS bearer identified by the TMGI of the MBMS bearer and additional parameters, like UDP port, associated to a group or the MBMS subchannel used to e.g. inform when a conversation in a group call is started or ended.
Media burst:
A flow of media from an MCPTT client that has the permission to send media.
Media plane control protocols:
Protocols in the media plane used for floor control, pre-established session call control and MBMS subchannel control.
Participating MCPTT function:
The MCPTT server performing a participating role.
Passive floor request queue:
The floor request queue used by the non-controlling MCPTT function to store received Floor Request messages for monitoring purposes.
For the purposes of the present document, the following terms and definitions given in TS 23.379 apply:
Ambient listening call
Floor control
Floor participant
Floor control server
Group call
MCPTT call
MCPTT server performing a controlling role
MCPTT server performing a participating role
MCPTT user
Mission critical push to talk
Multi-talker control
Private call
SIP core
For the purposes of the present document, the following terms and definitions given in TS 24.379 apply:
Non-controlling MCPTT function of an MCPTT group
For the purposes of the present document, the following terms and definitions given in TS 33.180 apply:
Client Server Key (CSK)
Client Server Key Identifier (CSK-ID)
Group Master Key (GMK)
Group Master Key Identifier (GMK-ID)
Multicast Key for Floor Control (MKFC)
Identifier of Multicast Key for Floor Control (MKFC-ID)
Multicast Signalling Key (MuSiK)
Multicast Signalling Key Identifier (MuSiK-ID)
Private Call Key (PCK)
Private Call Key Identifier (PCK-ID)
Signalling Protection Key (SPK)
Signalling Protection Key Identifier (SPK-ID)
MBMS SubChannel Control Key (MSCCK)
MBMS SubChannel Control Key Identifier (MSCCK-ID)
For the purposes of the present document, the following terms and definitions given in RFC 3711 apply:
SRTP master key (SRTP-MK)
SRTP master key identifier (SRTP-MKI)
SRTP master salt (SRTP-MS)
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3.2  AbbreviationsWord‑p. 19

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
AS
Application Server
CID
Context ID
CSK
Client Server Key
CSK-ID
Client Server Key Identifier
D2D
Device to Device
DL
Downlink
GCS AS
Group Communication Service Application Server
GMK
Group Master Key
GMK-ID
Group Master Key Identifier
GMS
Group Management Server
GUK-ID
Group User Key Identifier
IP
Internet Protocol
MBMS
Multimedia Broadcast and Multicast Service
MCMC
Mission Critical MBMS subchannel Control Protocol
MCPTT
Mission Critical Push To Talk
MKFC
Multicast Key for Floor Control
MKFC-ID
Identifier of Multicast Key for Floor Control (MKFC-ID)
MSCCK
MBMS SubChannel Control Key
MSCCK-ID
MBMS SubChannel Control Key Identifier
MuSiK
Multicast Signalling Key
MuSiK-ID
Multicast Signalling Key Identifier
PCK
Private Call Key
PCK-ID
Private Call Key Identifier
PTT
Push-To-Talk
RFC
Request For Comment
ROHC
Robust Header Compression
RTCP
RTP Control Protocol
RTP
Real-time Transport Protocol
SPK
Signalling Protection Key
SPK-ID
Signalling Protection Key Identifier
SRTCP
Secure RTCP
SRTP
Secure RTP
SRTP-MK
SRTP master key
SRTP-MKI
SRTP master key identifier
SRTP-MS
SRTP master salt
SSRC
Synchronization SouRCe
TMGI
Temporary Mobile Group Identity
UE
User Equipment
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