3GPP 38.300 v19.3.0 — the document's own text
4.3.2.1 Xn User Plane
Taught in 4. What NR is — the shape of the 5G radio network (TSG RAN — the group that specifies the radio, in depth), 2. The six working groups and the line between them (TSG RAN — the group that specifies the radio, overview), 4. What NR actually is, in the shape its own document gives it (TSG RAN — the group that specifies the radio, overview), 2. The six groups, and what each one worries about (TSG RAN — the group that specifies the radio, quick start), 3. What NR is, read off the document itself (TSG RAN — the group that specifies the radio, quick start).
The Xn User plane (Xn-U) interface is defined between two NG-RAN nodes. The user plane protocol stack on the Xn interface is shown in Figure 4.3.2.1-1. The transport network layer is built on IP transport and GTP-U is used on top of UDP/IP to carry the user plane PDUs.
Xn-U provides non-guaranteed delivery of user plane PDUs and supports the following functions:
- Data forwarding;
- Flow control.