3GPP TS 38.472 V15.0.0 (2017-12)Technical Specification3rd Generation Partnership Project;Technical Specification Group Radio Access Network;NG-RAN;F1 signalling transport(Release 15) The present document has been developed within the 3rd Generation Partnership Project (3GPP TM) and may be further elaborated for the purposes of 3GPP..The present document has not been subject to any approval process by the 3GPP Organizational Partners and shall not be implemented.This Specification is provided for future development work within 3GPP only. The Organizational Partners accept no liability for any use of this Specification.Specifications and Reports for implementation of the 3GPP TM system should be obtained via the 3GPP Organizational Partners' Publications Offices.3GPP TS 38.472 V15.0.0 (2017-12)8Release 15KeywordsNG RAN, Radio3GPPPostal address3GPP support office address650 Route des Lucioles - Sophia AntipolisValbonne - FRANCETel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16Internethttp://www.3gpp.orgCopyright NotificationNo part may be reproduced except as authorized by written permission.The copyright and the foregoing restriction extend to reproduction in all media.© 2017, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC).All rights reserved.UMTS™ is a Trade Mark of ETSI registered for the benefit of its members3GPP™ is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational PartnersLTE™ is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational PartnersGSM® and the GSM logo are registered and owned by the GSM AssociationContentsForeword 41 Scope 52 References 53 Definitions and abbreviations 53.1 Definitions 53.3 Abbreviations 64. F1-C signalling bearer 64.1 Function and protocol stack 65 Data link layer 66 IP layer 67 Transport layer 7Annex A (informative): Change History 8ForewordThis Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:Version x.y.zwhere:x the first digit:1 presented to TSG for information;2 presented to TSG for approval;3 or greater indicates TSG approved document under change control.y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.z the third digit is incremented when editorial only changes have been incorporated in the document.1 ScopeThe present document specifies the standards for Signalling Transport to be used across the F1 interface. The F1 interface provides means for interconnecting a gNB-CU and a gNB-DU of a gNB within an NG-RAN, or for interconnecting a gNB-CU and a gNB-DU of an en-gNB within an E-UTRAN. The present document describes how the F1AP signalling messages are transported over F1.2 ReferencesThe 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] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".[2] IETF RFC 2460 (1998-12): "Internet Protocol, Version 6 (IPv6) Specification".[3] IETF RFC 791 (1981-09): "Internet Protocol".[4] IETF RFC 2474 (1998-12): "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers".[5] IETF RFC 4960 (2007-09): "Stream Control Transmission Protocol".[6] 3GPP TS 38.300: "NR; Overall description; Stage-2".[7] 3GPP TS 38.401: "NG-RAN; Architecture description".[8] 3GPP TS 37.340: "NR; Multi-connectivity; Overall description; Stage-2".3 Definitions and abbreviations3.1 DefinitionsFor the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 [1].en-gNB: as defined in TS 37.340 [8]F1: interface between a gNB-CU and a gNB-DU, providing an interconnection point between the gNB-CU and the gNB-DU. F1-C: Reference point for the control plane protocol between gNB-CU and gNB-DU.gNB-CU: as defined in TS 38.401 [7]gNB-DU: as defined in TS 38.401 [7]gNB: as defined in TS 38.300 [6]3.3 AbbreviationsFor the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in 3GPP TR 21.905 [1].DiffServ Differentiated ServiceIANA Internet Assigned Number Authority IP Internet ProtocolPPP Point to Point ProtocolSCTP Stream Control Transmission Protocol4. F1-C signalling bearer4.1 Function and protocol stackF1-C signalling bearer provides the following functions:- Provision of reliable transfer of F1AP message over F1-C interface.- Provision of networking and routeing function.- Provision of redundancy in the signalling network.- Support for flow control and congestion control.The protocol stack for F1-C Signalling Bearer is shown in figure 4.1-1 and details on each protocol are described in the following clauses. Figure 4.1-1: F1-C signalling bearer protocol stackThe Transport Network Layer is based on IP transport, comprising SCTP on top of IP. 5 Data link layerThe support of any suitable Data Link Layer protocol, e.g. PPP, Ethernet, etc., shall not be prevented. 6 IP layerThe gNB-CU and gNB-DU shall support IPv6 (IETF RFC 2460 [2]) and/or IPv4 (IETF RFC 791 [3]).The IP layer of F1-C only supports point-to-point transmission for delivering F1AP message.The gNB-CU and gNB-DU shall support the Diffserv Code Point marking as described in IETF RFC 2474 [4].7 Transport layerSCTP (IETF RFC 4960 [5]) shall be supported as the transport layer of F1-C signalling bearer. The Payload Protocol Identifier assigned by IANA to be used by SCTP for the application layer protocol F1AP is 62.SCTP refers to the Stream Control Transmission Protocol developed by the Sigtran working group of the IETF for the purpose of transporting various signalling protocols over IP network.There shall be one or multiple SCTP association established between one gNB-CU and gNB-DU pair.The gNB-DU shall establish the SCTP association. The SCTP Destination Port number value assigned by IANA to be used for F1AP is 38472.Within the set of SCTP associations established between one gNB-CU and gNB-DU pair, a single SCTP association shall be employed for F1AP elementary procedures that utilize F1AP signalling not related to a UE, e.g., F1 Setup and Configuration Update, with the possibility of fail-over to a new association to enable robustness. Running other F1AP procedures over this same SCTP association is not precluded.Within an SCTP association established between one gNB-CU gNB-DU pair:- A single pair of stream identifiers shall be reserved for the sole use of F1AP elementary procedures that utilize non UE-associated signalling.- At least one pair of stream identifiers shall be reserved for the sole use of F1AP elementary procedures that utilize UE-associated signallings. However, a few pairs (i.e. more than one) should be reserved.- A single UE-associated signalling shall use one SCTP stream and the stream should not be changed during the communication of the UE-associated signalling.Transport network redundancy may be achieved by SCTP multi-homing between two end-points, of which one or both is assigned with multiple IP addresses. SCTP end-points shall support a multi-homed remote SCTP end-point. For SCTP endpoint redundancy an INIT may be sent from gNB-CU or gNB-DU, at any time for an already established SCTP association, which shall be handled as defined in IETF RFC 4960 [5] in sub clause 5.2.The SCTP congestion control may, using an implementation specific mechanism, initiate higher layer protocols to reduce the signalling traffic at the source and prioritise certain messages.Annex A (informative):Change HistoryChange historyDateMeetingTDocCRRevCatSubject/CommentNew version2017-06R3 NR#2R3-172121---First version0.1.02017-07R3 NR#2R3-172644---Incorporated agreed TPs from R3 NR#2 Adhoc0.2.02017-08R3#97R3-172715Incorporated Rapporteur's cleanup0.2.12017-08R3#97R3-173446---Incorporated agreed TPs from R3#970.3.02017-10R3#97bR3-174246---Incorporated agreed TPs from R3#97b0.4.02017-12R3#98R3-175062---Incorporated agreed TPs from R3#980.5.02017-12RAN#78RP-172261Submitted for approval to RAN1.0.02017-12RAN#78TR approved by RAN plenary15.0.03GPP。