TS 25.432
UTRAN – Iub Interface –
Signalling Transport

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Rapporteur:: Mr. Wilson, Mick

Content for TS 25.432 Word version: 18.0.0

1 Scope p. 5

The present document specifies the signalling transport related to NBAP signalling to be used across the Iub Interface. The Iub interface is a logical interface for the interconnection of Node B and Radio Network Controller (RNC) components of the UMTS Terrestrial Radio Access Network (UTRAN) for the UMTS system. The radio network control signalling between these nodes is based on the Node B application part (NBAP).

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.2130 (1994-07): "B-ISDN signalling ATM adaptation layer - Service specific coordination function for support of signalling at the user network interface (SSCF-UNI)".

[3]

ITU-T Recommendation Q.2110 (1994-07): "B-ISDN ATM adaptation layer - Service specific connection oriented protocol (SSCOP)".

[4]

ITU-T Recommendation I.363.5 (1996-08): "B-ISDN ATM Adaptation LayerSpecification : Type 5 AAL".

[5]

ITU-T Recommendation I.361 (1995-11): "B-ISDN ATM layer specification".

[6]

ITU-T Recommendation I.630 (1999-02): "ATM protection switching".

[7]

RFC 2960 (2000-10): "Stream Control Transmission Protocol".

[8]

RFC 2460 (1998-12): "Internet Protocol, Version 6 (IPv6) Specification".

[9]

RFC 791 (1981-09): "Internet Protocol".

[10]

RFC 2474 (1998-12): "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers".

[11]

RFC 1661 (1994-07): "The Point-to-Point Protocol (PPP)".

[12]

RFC 1662 (1994-07): "PPP in HDLC-like Framing".

[13]

RFC 2507 (1999-02): "IP header compression".

[14]

RFC 1990 (1996-08): "The PPP Multilink Protocol (MP)".

[15]

RFC 2686 (1999-09): "The Multi-Class Extension to Multi-Link PPP".

[16]

RFC 2509 (1999-02): "IP Header Compression over PPP".

[17]

RFC 3153 (2001-08): "PPP Multiplexing".

[18]

RFC 2364 (1998-07): "PPP over AAL5".

[19]

RFC 3031 (2001-01): "Multiprotocol Label Switching Architecture".

[20]

RFC 3309 (2002-09): "Stream Control Transmission Protocol (SCTP) Checksum Change".

[21]

TS 25.433: "UTRAN Iub interface Node B Application Part (NBAP) signalling".

3 Definitions, symbols and abbreviations p. 6

3.1 Definitions p. 6

For the purposes of the present document, the following terms and definitions apply:

IP UTRAN node:

An UTRAN Node supporting the IP Transport Option

3.2 Symbols p. 6

(void)

3.3 Abbreviations p. 6

AAL

ATM Adaptation Layer

ATM

Asynchronous Transfer Mode

HDLC

High-level Data Link Control

Internet Protocol

NBAP

Node B Application Part

PPP

Point-to-Point Protocol

RNC

Radio Network Controller

SAAL

Signalling ATM Adaptation Layer

SCTP

Stream Control Transmission Protocol

SSCF

Service Specific Coordination Function

SSCOP

Service Specific Connection Oriented Protocol

UNI

User-Network Interface

4 Data Link Layer p. 6

4.1 ATM Transport Option p. 6

ATM shall be used in the radio network control plane according to ITU-T Rec. I.361 [5].

4.1.1 Protection switching at ATM Layer p. 6

If redundancy of pathways at ATM layer between RNC and Node B is supported, it shall be implemented using ATM Protection Switching according to ITU-T Rec. I.630 [6].

4.2 Data Link Layer for IP Transport Option p. 6

A RNC or Node B supporting IP Transport Option shall support the PPP protocol with HDLC framing (IETF RFC 1661 [11], IETF RFC 1662 [12]).

A RNC or Node B supporting IP transport option and having interfaces connected via slow bandwidth PPP links like E1/T1/J1 shall also support IP Header Compression (IETF RFC 2507 [13]) and the PPP extensions ML/MC-PPP (IETF RFC 1990 [14], IETF RFC 2686 [15]). In this case, negotiation of header compression (IETF RFC 2507 [13]) over PPP shall be performed via (IETF RFC 2509 [16]).

5 NBAP signalling bearer p. 7

5.1 Introduction p. 7

The Signalling Bearer for NBAP (TS 25.433) is a point-to-point protocol. There may be multiple point-to-point links between an RNC and a Node B. As shown in Figure 1, the standard allows operators to choose one out of two protocol suites for transporting the NBAP messages.

Copy of original 3GPP image for 3GPP TS 25.432, Fig. 1: Iub NBAP Signalling Transport

Figure 1: Iub NBAP Signalling Transport
(⇒ copy of original 3GPP image)

5.2 Signalling bearer in case of ATM Transport Option p. 7

The signalling bearer in the Radio Network Control Plane is SAAL-UNI (ITU-T Rec. Q.2100 [1]) over ATM. The protocols to be used to support NBAP signalling are SSCF-UNI (ITU-T Rec. Q.2130 [2]) on top of SSCOP (ITU-T Rec. Q.2110 [3]) and AAL Type 5 (ITU-T Rec. I.363.5 [4]).

5.3 Signalling bearer in case of IP Transport Option p. 7

SCTP (IETF RFC 2960 [7]) over IP shall be supported as the transport for NBAP signalling bearer on Iub Interface. A RNC equipped with the SCTP stack option shall initiate the INIT procedure for establishing association. The data link layer is as specified in chapter 4.2.

The checksum method specified in IETF RFC 3309 [20] shall be used instead of the method specified in IETF RFC 2960 ([7]).

An IP UTRAN node shall support IPv6 (IETF RFC 2460 [8]). The support of IPv4 (IETF RFC 791 [9]) is optional.

IP dual stack is recommended for the potential transition period from IPv4 to IPv6 in the transport network.

Each signalling bearer between the RNC and Node B shall correspond to one single SCTP stream in UL and one single SCTP stream in DL direction, both streams belonging to the same SCTP association.

IP Differentiated Services code point marking (IETF RFC 2474 [10]) shall be supported. The Diffserv code point may be determined from the application parameters.