The present document specifies the NR user plane protocol functions used within NG-RAN and, for EN-DC and LTE UP-CP split within E-UTRAN. NR user plane protocol functions may reside in nodes terminating either the X2-U (for EN-DC) or the Xn-U or the F1-U interface. User plane protocol functions support both E-UTRA PDCP and NR PDCP.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
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For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
a node interacting with a node hosting PDCP for flow control. In an IAB network, this is the IAB-DU serving the UE for the corresponding data radio bearer.
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.
The NR user plane protocol is located in the User Plane of the Radio Network layer over either the Xn or the X2 or the F1 interface or the UP interface between eNB-CP and eNB-UP.
The NR user plane protocol is used to convey control information related to the user data flow management of data radio bearers.
Each NR user plane protocol instance is associated to one data radio bearer only. There is one NR user plane instance per GTP tunnel. When a GTP tunnel is set up, a new NR user plane instance is set up.
If configured, NR user plane protocol instances exist at the Master node and the Secondary node in the context of DC or at nodes hosting F1-U protocol terminations or at eNB-CP and eNB-UP. The NR user plane protocol supports direct communication between NR user plane protocol entities, regardless of whether they terminate the same or different user plane interfaces.
On each data radio bearer, the NR user plane protocol operates with RLC AM or RLC UM.
In this version of the present document, NR user plane protocol data is conveyed by GTP-U protocol means, more specifically, by means of the "NR RAN Container" GTP-U extension header as defined in TS 29.281.