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TS 25.412
UTRAN – Iu Interface –
Signalling Transport

3GPP‑Page   ETSI‑search   CONTENT↓
V18.0.0 (PDF)  2024/03  13 p.
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Rapporteur:
Mr. Ng, Cheng Hock
NEC Corporation

Content for  TS 25.412  Word version:  18.0.0

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1  Scope  p. 5

The present document specifies the standards for Signalling Transport to be used across Iu Interface. Iu Interface is a logical interface between the RNC and the UTRAN Core Network. The present document describes how the RANAP signalling messages are transported over Iu.

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]
ITU-T Recommendation Q.2100 (1994-07): "B-ISDN Signalling ATM Adaptation Layer (SAAL) - overview description".
[2]
ITU-T Recommendation Q.2110 (1994-07): "B-ISDN ATM Adaptation Layer - Service Specific Connection Oriented Protocol (SSCOP)".
[3]
ITU-T Recommendation Q.2140 (1995-02): "B-ISDN ATM adaptation layer - Service Specific Co-ordination Function for signalling at the Network Node Interface (SSCF AT NNI)".
[4]
ITU-T Recommendation Q.2210 (1996-07): "Message transfer part level 3 functions and messages using the services of ITU-T Recommendation Q.2140".
[5]
ITU-T Recommendation I.361 (1995-11): "B-ISDN ATM layer specification".
[6]
ITU-T Recommendation I.363.5 (1996-08): "B-ISDN ATM Adaptation Layer Type 5".
[7]
ITU-T Recommendation Q.711 (1996-07): "Functional description of the signalling connection control part".
[8]
ITU-T Recommendation Q.712 (1996-07): "Definition and function of Signalling connection control part messages".
[9]
ITU-T Recommendation Q.713 (1996-07): "Signalling connection control part formats and codes".
[10]
ITU-T Recommendation Q.714 (1996-07): "Signalling connection control part procedures".
[11]
ITU-T Recommendation Q.715 (1996-07): "Signalling connection control part user guide".
[12]
ITU-T Recommendation Q.716 (1993-03): "Signalling Connection Control Part (SCCP) performance".
[13]
RFC 791  (1981-09): "Internet Protocol".
[14]
RFC 2684  (1999-09): "Multiprotocol Encapsulation over ATM Adaptation Layer 5".
[15]
RFC 2225  (1998-04): "Classical IP and ARP over ATM".
[16]
RFC 2960  (2000-10): "Stream Control Transmission Protocol".
[17]
RFC 3332(2002-09):  "Signalling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA)"
[18]
TS 25.410: "UTRAN Iu Interface: General Aspects and Principles".
[19]
RFC 1661  (1994-07): "The Point-To-Point Protocol (PPP)".
[20]
RFC 1662  (1994-07): "PPP in HDLC-like Framing".
[21]
RFC 2507  (1999-02): "IP header compression".
[22]
RFC 1990  (1996-08): "The PPP Multilink Protocol (MP)".
[23]
RFC 2686  (1999-09): "The Multi-Class Extension to Multi-Link PPP".
[24]
RFC 2509  (1999-02): "IP Header Compression over PPP".
[25]
RFC 2460  (1996-12): "Internet Protocol, Version 6 (Ipv6) Specification".
[26]
RFC 2474  (1998-12): "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers".
[27]  Void.
[28]
RFC 3031  (2001-01): "MPLS".
[29]
RFC 3153  (2001-08): "PPPmultiplexing".
[30]
RFC 3309  (2002-09): "SCTP Checksum Change".
[31]
ANSI T1.111-2001: "Signalling System Number 7 (SS7) - Message Transfer Part (MTP)".
[32]
ANSI T1.112-2001: "Signalling System Number 7 (SS7) -- Signalling Connection Control Part (SCCP)".
[33]
ANSI T1.645-1995 (R2003), "B-ISDN Signaling ATM Adaptation Layer - Service Specific Coordination Function for Support of Signaling at the Network Node Interface (SSCF at the NNI)".
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3  Abbreviations  p. 6

For the purposes of the present document, the following abbreviations apply:
AAL
ATM Adaptation Layer
AAL2
ATM Adaptation Layer 2
AAL5
ATM Adaptation Layer 5
ATM
Asynchronous Transfer Mode
CS
Circuit Switched
DiffServ
Differentiated Services
HDLC
High Level Data Link Control
IP
Internet Protocol
M3UA
SS7 MTP3 User Adaptation Layer
ML/MC-PPP
Muti-Link/Multi-Class PPP
MPLS
Multiprotocol Label Switching
MSC
Mobile services Switching Center
MTP3-B
Message Transfer Part
PPP
Point-to-Point protocol
PPPMux
PPP Multiplexing
PS
Packet Switched
RANAP
Radio Access Network Application Part
RNC
Radio Network Controller
SAAL-NNI
Signalling ATM Adaptation Layer - Network Node Interface
SCCP
Signalling Connection Control Part
SCTP
Stream Control Transmission Protocol
SGSN
Serving GPRS Support Node
SSCF
Service Specific Co-ordination Function
SSCOP
Service Specific Connection Oriented Protocol
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4  Data Link Layer  p. 7

4.1  ATM Transport Option  p. 7

ATM shall be used in the radio network control plane according to (ITU-T Rec. I.361 [5]). The structure of the cell header used in the UTRAN Iu interface is the cell header format and encoding at NNI (see Figure 3/I.361).

4.2  IP Transport Option |R5|  p. 7

An RNC/CN using IP transport option shall support the PPP protocol with HDLC framing (RFC 1661, RFC 1662).
An RNC/CN using IP transport option having interfaces connected via low bandwidth PPP links like E1/T1/J1 shall also support IP Header Compression (RFC 2507) and the PPP extensions ML/MC-PPP (RFC 1990, RFC 2686). In this case, the negotiation of header compression (RFC 2507) over PPP shall be performed via RFC 2509.
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5  RANAP Signalling Bearer  p. 7

5.1  Introduction  p. 7

This subclause specifies the Signalling Bearer protocol stack that supports the RANAP signalling protocol.
The following requirements on the Signalling Bearer can be stated:
  • provide reliable transfer of control plane signalling messages in both connectionless mode and connection-oriented mode;
  • provide separate independent connections for distinguishing transactions with individual UE's;
  • supervise the 'UE connections' and provide connection status information to the Upper Layers for individual UE's;
  • provide networking and routing functions;
  • provide redundancy in the signalling network;
  • provide load sharing.
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5.2  Signalling Bearer for Circuit Switched Domain  p. 7

5.2.1  Protocol Stack for the CS Domain  p. 7

The protocol stacks for the CS Domain are shown in Figure 1. The standard allows operators to choose one out of two standardised protocol suites for transport of SCCP messages.
Figure 1 shows, for the Iu IP CS domain, the point at which the service primitives are invoked. A single SAP is defined independently of the signalling bearer. The SAP provides the SCCP primitives. The Figure is not intended to constrain the architecture.
The following Figure 1 also illustrates the protocol model having Broadband Signalling System No.7 as the signalling bearer for RANAP over the Iu interface that fulfils the requirements. Figure 1 shows, for the CS domain, the point at which the service primitives are invoked. The SAP provides the SCCP primitives.
Reproduction of 3GPP TS 25.412, Fig. 1: SAP between RANAP and its transport for Iu - CS Domain
Figure 1: SAP between RANAP and its transport for Iu - CS Domain
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5.2.2  ATM Transport Option |R5|  p. 8

1)
SCCP (ITU-T Rec. Q.711 [7] or ANSI T1.112-2001 [32]) provides connectionless service, class 0, connection oriented service, class 2, separation of the connections mobile by mobile basis on the connection oriented link and establishment of a connection oriented link mobile by mobile basis. SCCP shall be used as specified in TS 25.410.
2)
MTP3-B (ITU-T Rec. Q.2210 [4] or ANSI T1.111-2001 [31]) provides message routing, discrimination and distribution (for point-to-point link only), signalling link management load sharing and changeover/back between link within one link-set. The need for multiple link-sets is precluded. MTB3-B shall comply with ITU-T Rec. Q.2210 [4] or ANSI T1.111-2001 [31].
3)
SAAL-NNI (ITU-T Rec. Q.2100 [1]) consists of the following sub-layers: - SSCF (ITU-T Rec. Q.2140 [3] or ANSI T1.645-1995 (R2003) [33]), - SSCOP (ITU-T Rec. Q.2110 [2]) and - AAL5 (ITU-T Rec. I.363.5 [6]). The SSCF maps the requirements of the layer above to the requirements of SSCOP. Also SAAL connection management, link status and remote processor status mechanisms are provided. SSCOP provides mechanisms for the establishment and release of connections and the reliable exchange of signalling information between signalling entities. Adapts the upper layer protocol to the requirements of the Lower ATM cells. It shall be possible to use SAAL-NNI connections pre-configured as PVCs for signalling transport on the Iu-Interface.
4)
ATM (ITU-T Rec. I.361 [5]).
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5.2.3  IP Transport Option |R5|  p. 8

1)
SCCP, see subclause 5.2.2.
2)
M3UA refers to the SCCP adaptation layer "SS7 MTP3 - User Adaptation Layer" (RFC 3332) also developed by the Sigtran working group of the IETF. An RNC equipped with the M3UA stack option shall have client functionality. This enables the RNC to report to the MSC when it is a newly introduced entity in the network.
3)
SCTP refers to the Stream Control Transmission Protocol (RFC 2960) developed by the Sigtran working group of the IETF for the purpose of transporting various signalling protocols over IP networks. The checksum method specified in RFC 3309 shall be used instead of the method specified in RFC 2960. Multi-homing is a way to achieve redundancy with SCTP between two endpoints, of which one or both is assigned with multiple IP addresses. SCTP endpoints shall support a multi-homed remote SCTP endpoint.
4)
IP. IPv6 shall be supported according to RFC 2460. IPv4 support (RFC 791) is optional.
Due to the possible transition from IPv4 to IPv6 the IP dual stack support is recommended.
An RNC/CN using IP transport option shall support Diffserv code point marking RFC 2474. The Diffserv code point may be determined from the application parameters.
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5.3  Signalling Bearer for Packet Switched Domain  p. 9

5.3.1  Protocol Stack for the PS Domain  p. 9

The protocol stacks for the PS Domain is shown in Figure 2. The standard allows operators to choose one out of three standardised protocol suites for transport of SCCP messages.
Reproduction of 3GPP TS 25.412, Fig. 2: SAP between RANAP and its transport for the Iu -IP domain
Figure 2: SAP between RANAP and its transport for the Iu -IP domain
Up
Figure 2 shows, for the Iu IP domain, the point at which the service primitives are invoked. A single SAP is defined independently of the signalling bearer. The SAP provides the SCCP primitives. The Figure is not intended to constrain the architecture.

5.3.2  ATM Transport Option 1  p. 9

1)
SCCP (ITU-T Rec. Q.711 [7] /ITU-T Rec. Q.712 [8] /ITU-T Rec. Q.713 [9] /ITU-T Rec. Q.714 [10] /ITU-T Rec. Q.715 [11] /ITU-T Rec. Q.716 [12] or ANSI T1.112-2001 [32]) provides connectionless service, class 0, connection oriented service, class 2, separation of the connections mobile by mobile basis on the connection oriented link and establishment of a connection oriented link mobile by mobile basis. The SCCP shall be used as specified in TS 25.410.
2)
MTP3-B (ITU-T Rec. Q.2210 [4] or ANSI T1.111-2001 [31]) provides message routing, discrimination and distribution (for point-to-point link only), signalling link management load sharing and changeover/back between link within one link-set. The need for multiple link-sets is precluded. MTB3-B shall comply with ITU-T Rec. Q.2210 [4] or ANSI T1.111-2001 [31].
3)
SAAL-NNI (ITU-T Rec. Q.2100 [1]) consists of the following sub-layers: - SSCF-NNI (ITU-T Rec. Q.2140 [3] or ANSI T1.645-1995 (R2003) [33]), - SSCOP (ITU-T Rec. Q.2110 [2]) and - AAL5 (ITU-T Rec. I.363.5 [6]). The SSCF maps the requirements of the layer above to the requirements of SSCOP. Also SAAL connection management, link status and remote processor status mechanisms are provided. SSCOP provides mechanisms for the establishment and release of connections and the reliable exchange of signalling information between signalling entities. Adapts the upper layer protocol to the requirements of the Lower ATM cells. It shall be possible to use SAAL-NNI connections pre-configured as PVCs for signalling transport on the Iu-interface.
4)
ATM (ITU-T Rec. I.361 [5]).
Up

5.3.3  ATM Transport Option 2 |R5|  p. 10

1)
SCCP, see subclause 5.3.2.
2)
M3UA refers to the SCCP adaptation layer "SS7 MTP3 - User Adaptation Layer" (RFC 3332) also developed by the Sigtran working group of the IETF. An RNC equipped with the M3UA stack option shall have client functionality. This enables the RNC to report to the SGSN when it is a newly introduced entity in the network.
3)
SCTP refers to the Stream Control Transmission Protocol (RFC 2960) developed by the Sigtran working group of the IETF for the purpose of transporting various signalling protocols over IP networks. The multi-homing services of SCTP shall be required at both ends of an SCTP-association to enable transport redundancy and reliability. M3UA. An implementation of SCTP to this document shall utilise the new checksum method specified in RFC 3309 instead of the method specified in RFC 2960.
4)
IP (RFC 791) over ATM is defined in RFC 2684 and RFC 2225.
5)
AAL5 refers to ITU-T Rec. I.363.5 [6]. It shall be possible to use AAL5 connections pre-configured as PVCs for signalling transport on the Iu-interface.
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5.3.4  IP Transport Option |R5|  p. 10

1)
SCCP , see subclause 5.3.2.
2)
M3UA, refers to the SCCP adaptation layer "SS7 MTP3 - User Adaptation Layer" (RFC 3332) also developed by the Sigtran working group of the IETF. An RNC equipped with the M3UA stack option shall have client functionality. This enables the RNC to report to the SGSN when it is a newly introduced entity in the network.
3)
SCTP, refers to the Stream Control Transmission Protocol (RFC 2960) developed by the Sigtran working group of the IETF for the purpose of transporting various signalling protocols over IP networks. An implementation of SCTP to this document shall utilise the new checksum method specified in RFC 3309 instead of the method specified in RFC 2960. Multi-homing is a way to achieve redundancy with SCTP between two endpoints, of which one or both is assigned with multiple IP addresses. SCTP endpoints shall support a multi-homed remote SCTP endpoint.
4)
IP. IPv6 shall be supported according to RFC 2460. IPv4 support (RFC 791) is optional.
Due to the possible transition from IPv4 to IPv6, the IP dual stack support is recommended.
An RNC/CN using IP transport option shall support Diffserv code point marking (RFC 2474). The Diffserv code point may be determined from the application parameters.
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5.4  Services Provided by the Signalling Bearer  p. 10

When considering the requirements that the upper layers, i.e. RANAP, have on the Signalling Bearer, there are a number of services it has to provide and a number of functions to perform. These numbers of services that the signalling bearer shall provide, to the upper layers, are stated in references ITU-T Rec. Q.711 [7] /ITU-T Rec. Q.712 [8] /ITU-T Rec. Q.713 [9] /ITU-T Rec. Q.714 [10] /ITU-T Rec. Q.715 [11] / ITU-T Rec. Q.716 [12] or ANSI T1.112-2001 [32].
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$  Change History  p. 11

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