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TS 38.414
NG-RAN — NG interface –
Data Transport

3GPP‑Page   ETSI‑search   CONTENT↓
V18.0.0 (PDF)  2024/03  10 p.
V17.0.0  2022/03  10 p.
V16.0.0  2020/06  10 p.
V15.3.0  2020/06  10 p.
Rapporteur:
Mr. Li, Dapeng
ZTE Corporation

Content for  TS 38.414  Word version:  18.0.0

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1  Scope  p. 5

The present document specifies the standards for user data transport protocols and related signalling protocols to establish user plane transport bearers over the NG interface.

2  References  p. 5

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 23.501: "System Architecture for the 5G System; Stage 2".
[3]
TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)".
[4]
RFC 768  (1980-08): "User Datagram Protocol".
[5]
RFC 8200  (2017-07): "Internet Protocol, Version 6 (IPv6) Specification".
[6]
RFC 791  (1981-09): "Internet Protocol".
[7]
RFC 2474  (1998-12): "Definition of the Differentiated Services Field (DS Field) in the Ipv4 and Ipv6 Headers".
[8]
TS 38.300: "NR and NG-RAN Overall Description Stage 2"
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3  Definitions and abbreviations  p. 5

3.1  Definitions  p. 5

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.
gNB:
as defined in TS 38.300.
ng-eNB:
as defined in TS 38.300.
NG-RAN node:
as defined in TS 38.300.
NG-U:
as defined in TS 38.300.
PDU Session:
as defined in TS 23.501.

3.2  Abbreviations  p. 6

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.
5GC
5G Core
5QI
5G QoS Identifier
AMF
Access and Mobility Management Function
GTP
GPRS Tunnelling Protocol
IP
Internet Protocol
NGAP
NG Application Protocol
TEID
Tunnel Endpoint Identifier
UDP
User Datagram Protocol
UPF
User Plane Function
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4  Data Link Layer  p. 6

Any data link protocol that fulfills the requirements toward the upper layer may be used.

5  NG Interface user plane protocol  p. 6

5.1  General  p. 6

Both gNB and ng-eNB can be connected to the 5GC over the NG interface.
The transport layer for data streams over NG is an IP based Transport. The following Figure shows the transport protocol stacks over NG.
Reproduction of 3GPP TS 38.414, Fig. 5.1: Transport network layer for data streams over NG
Figure 5.1: Transport network layer for data streams over NG
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The GTP-U (TS 29.281) protocol over UDP over IP shall be supported as the transport for data streams on the NG interface. The data link layer is as specified in clause 4.
The transport bearer is identified by the GTP-U TEID (TS 29.281) and the IP address (source TEID, destination TEID, source IP address, destination IP address).
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5.2  GTP-U  p. 6

The GTP-U (TS 29.281) protocol shall be used over the NG-U interface toward the 5GC.

5.3  UDP/IP  p. 6

The path protocol used shall be UDP (IETF RFC 768).
The UDP port number for GTP-U shall be as defined in TS 29.281.
The NG-RAN node and the 5GC shall support fragmentation and assembly of GTP packets at the IP layer.
The NG-RAN node and the 5GC shall support IPv6 (IETF RFC 8200) and/or IPv4 (IETF RFC 791).
There may be one or several IP addresses in the NG-RAN node and in the 5GC. The packet processing function in the 5GC shall send downstream packets of a given PDU Session to the NG-RAN node IP address (received in NGAP) associated to that particular PDU Session. The packet processing function in the NG-RAN node shall send upstream packets of a given PDU Session to the 5GC IP address (received in NGAP) associated to that particular PDU Session.
The Transport Layer Address signalled in NGAP messages is a bit string of
  1. 32 bits in case of IPv4 address according to IETF RFC 791; or
  2. 128 bits in case of IPv6 address according to IETF RFC 8200; or
  3. 160 bits if both IPv4 and IPv6 addresses are signalled, in which case the IPv4 address is contained in the first 32 bits.
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5.4  Diffserv code point marking  p. 7

IP Differentiated Services code point marking (IETF RFC 2474) shall be supported. The mapping between traffic categories and Diffserv code points shall be configurable by O&M based on 5QI, the Priority Level (if explicitly signalled), and other NG-RAN traffic parameters (e.g. ARP). Traffic categories are implementation-specific and may be determined from the application parameters.

$  Change history  p. 8

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