1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU B-ISDN ATM ADAPTATION LAYER (2.21 40 (02195) B-ISDN ATM ADAPTATION LAYER - SERVICE SPECIFIC COORDINATION FUNCTION FOR SIGNALLING AT THE NETWORK NODE INTERFACE (SSCF AT NNI) ITU-T Recommendation Q.2140 (Previo
2、usly “CCITT Recornmendation”) -ITU-T RECMN*Q02140 95 m 4862593 Ob03409 97T m FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issu
3、ing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on
4、 these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation 4.2140 was prepared by ITU-T Study Group 11 (1993-1996) and was approved under the WTSC Resolution No. 1 proced
5、ure on the 7th of February 1995. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1995 All rights reserved. No part of this publication may be reproduced or utilized in an
6、y form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*Q.2140 95 m 4862591 Oh03430 691 1 2 3 4 5 6 7 8 9 10 11 12 CONTENTS Scope Normative References Abbreviations . General . Services provided by the SAAL at th
7、e NNI . Functions of the SSCF at the NNI 6.1 Functions with no peer-to-peer messages . 6.2 Functions with peer-to-peer messages 6.3 Signalling protocol stack for NNI . Definition of the boundary between the SSCF with Layer 3 at the NNI . 7.1 Primitives 7.2 State transition diagram Definition of the
8、boundary between the SSCF at the NNI and the SSCOP . 8.1 Repertoire of signals between SSCF and SSCOP . 8.2 Sequences of signals between SSCF and SSCOP . Definition of the boundary between the SSCF and the Layer Management Protocol elements for peer-to-peer Communication Default parameters and timer
9、s State transition table of SSCF at the NNI . Annex A . Protocol Implementation Conformance Statement (PICS) pro formato Recommendation 4.2140 A.l General A.2 Abbreviations and special symbols . A.3 Instructions for completing the PICS pro forma . A.4 Global statement of conformance . AS SSCOP - Rec
10、ommendation Q.2110 . A.6 SSCF at NNI -Recommendation 4.2140 Appendix I - Impacts of SAAL on MTP-3 1.1 Frame format of MTP-3 + B-ISUP message 1.2 Octet transmission order . 1.3 Size of FSN in changeover message . 1.4 Proving ends due to a processor outage condition 1.5 Automatic allocation of signall
11、ing data links . Appendix II - Example time flow diagrams for connection establishment Appendix III - SDL Diagrams for the SSCF at the NM Recommendation Q.2140 (02/95) Page 1 1 2 3 3 4 4 5 8 9 9 11 12 12 14 15 16 17 17 30 30 30 30 31 31 33 36 36 36 37 31 37 38 41 I SUMMARY The ATM Adaptation Layer (
12、AAL) is defined to enhance the services provided by the ATM layer to support the functions required by the next higher layer. One particular type of AAL service is the signalling AAL (SAAL) which comprises AAL functions necessary to support a signalling. The structure of the SAAL is defined in Recom
13、menda- tion Q.2100 8. The SAAL consists of a Segmentation and Reassembly (SAR) function, and a Convergence Sublayer which is specified as two sublayers: a Common Part Convergence Sublayer (CPCS) and a Service Specific Convergence Sublayer (SSCS). The CPCS is defined in clause 6h.363 5 and is used as
14、 the underlying protocol for the service specific part for signalling. The SSCS is functionally divided into two parts: the Service Specific Connection Oriented Protocol (SSCOP), which provides an assured data transfer service and the Service Specific Coordination Function (SSCF). The SSCOP is defin
15、ed in Recommendation Q.2110 9 and is suitable for use by various SSCFs. This Recommendation specifies the SSCF for signalling at the Network Node Interface (NNI). The SSCF at the NNI performs a coordination function between the service required by the signalling layer 3 user and the service provided
16、 by SSCOP. This Recommendation describes for the SSCF at the NNI the mapping of primitives from layer 3 to signals of the SSCOP and vice versa. Similarly, it specifies the exchange of signals between layer management and the SSCF at the NNI. Keywords ATM Asynchronous Transfer Mode AAL ATM Adaptation
17、 Layer B-ISDN Broadband Integrated Services Digital Network MTP Message Transfer Part (of Signalling System No. 7) NNI Network Node Interface SAAL Signalling AAL SSCF Service Specific Coordination Function SSCOP Service Specific Connection Oriented Protocol 11 Recommendation Q.2140 (02/95) ITU-T REC
18、MN*Q=ZLqO 95 m 4862591 O603412 4b4 m Recommendation Q.2140 B-ISDN ATM ADAPTATION LAYER - SERVICE SPECIFIC COORDINATION FUNCTION FOR SIGNALLING AT THE NETWORK NODE INTERFACE (SSCF AT NNI) (Geneva, 1995) 1 Scope This Recommendation specifies a function that is part of the ATM Adaptation Layer to suppo
19、rt signalling (SAAL) at the Network Node Interface (NNI) of the B-ISDN. This function is used to map the service of the Service Specific Connection Oriented Protocol (SSCOP) of the AAL to the requirements of an SAAL user at the NNI as defined in Recommendation Q.704 6. These requirements cover the n
20、eeds for signalling between network nodes and networks. This function is called Service Specific Coordination Function (SSCF) for signalling at the NNI. This Recommendation covers the specification of the SSCF identified in the complete AAL structure for signalling applications at the NNI defined in
21、 Recommendation Q.2100 8, and describes the interactions with the level 3 protocol entity for network node signalling as defined in Recommendation Q.704 6, layer management defined in Recommendation 4.2144 7 and the Service Specific Connection Oriented Protocol defined in Q.2110 191. This Recommenda
22、tion is applicable to equipment to be attached to a B-ISDN Network Node Interface when B-ISDN inter-nodal signalling is to be supported. Although this Recommendation refers to MTP-3 6 to identify user requirements, this SSCF may be utilized by other protocol entities which are able to rely on the SS
23、CF services specified in this Recommendation. 2 Normative References The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommend
24、ations and other references are subject to revision: all users ot this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly
25、 published. CCITT Recommendation X.200 (1988), Reference model of Open Systems Interconnection for CClV applications. CCITT Recommendation X.210 (1988), Open Systems Interconnection layer service definition conventions. ITU-T Recommendation 1.361 (1993), B-ISDNATM layer specifcation. ITU-T Recommend
26、ation 1.150 (1993), B-ISDN asynchronous transfer mode functional characteristics. ITU-T Recommendation 1.363 (1993), B-ISDN ATM Adaptation hyer (AAL) specGcation. ITU-T Recommendation Q.704 (1993), Signalling System No. 7 - Signalling network functions and messages. ITU-T Recommendation Q.2 144 (199
27、5), B-ISDN Signalling ATM adaptation layer - Layer management for the SAAL at the network mode intelface. Recommendation Q.2140 (02/95) 1 ITU-T Recommendation 4.2100 (1994), B-ISDN Signalling ATMAdaptation Layer (SAAL) overview description. ITU-T Recommendation Q.2110 (1994), B-ISDN ATM adaptation l
28、ayer - Service Specific Connection Oriented Protocol (SSCOP). CCITT Recommendation X.290 (1992), OSI conformance testing methodology and framework for protocol recommendations for CCIT applications - General concepts. Abbreviations For the purposes of this Recommendation, the following abbreviations
29、 are used: AAL ALN ANS ATM BR BSNT cc CD CES CP CPCS FSNC INS LM LPO LR MAAL MI MPS MTP MU NNI 00s PDU PDUT PE PNS PO RN RR SAAL SAP SAR ATM Adaptation Layer Alignment Alignment Not Successful Asynchronous Transfer Mode Buffer Release Backward Sequence Number to be Transmitted Congestion Ceased Cong
30、estion Detected Connection Endpoint Suffix Common Part CP Convergence Sublayer Forward Sequence Number of last message signal unit accepted by remote peer In Service Layer Management Local Processor Outage Local Release Management ATM Adaptation Layer Management Initiated Management Proving State Me
31、ssage Transfer Part (of Signalling System No. 7) Message Unit Network Node Interface Out Of Service Protocol Data Unit PDU Transmitted Protocol Error Proving Not Successful Processor Outage Retrieval Number Remote Release Signalling AAL Service Access Point Segmentation And Reassembly 2 Recommendati
32、on Q.2140 (OW95) SD SN SR SREC SSCF SSCOP SSCS UDR UNI UPS uu VCI Sequence Data Sequence Number SSCOP Release SSCOP Recover Service Specific Coordination Function Service Specific Connection Oriented Protocol Service Specific Convergence Sublayer UNITDATA Received Work Interface User Proving State U
33、ser to User Virtual Channel Identifier 4 General The Service Specific Coordination Function (SSCF) specified in this Recommendation in conjunction with the Service Specific Connection Oriented Protocol (SSCOP) specified in Recommendation 4.21 10 9 define the Service Specific Convergence Sublayer (SS
34、CS). The purpose of the Service Specific Coordination Function is to enhance the services of SSCOP to meet the needs of the requirements of the NNI level 3 protocol. In addition the SSCF at the NNI provides communication with Layer Management for proper operation of signalling links. Figure VQ.2100
35、8 illustrates the structure of the SAAL at the NNI. It comprises the SSCF at the NNI (this Recommendation), the SSCOP 9, the SSCS Layer Management 7, and the AAL type 5 common part (clause 6 of 5). One user of this Recommendation is MTP level 3 6. This sub-layer (the SSCF at the NNI) has common inte
36、rfaces with the MTP level 3, the SSCS Layer Management, and the SSCOP. The definition of the SAAL takes into consideration the principles and terminology of Recommendations X.200 l and X.210 2 - the reference model and layer service conventions for Open Systems Interconnection (0%). The SAAL is a pr
37、otocol which operates at the data link layer of the OS1 architecture. NOTES 1 The ATM layer is currently defined in Recommendations 1.150 4 and 1.361 3. Level 3 is defined in Recommendation Q.704 6 for the NNI. 2 The term “level 3” is used to indicate the layer above the SAAL, the user of the SAAL s
38、ervices. 5 Services provided by the SAAL at the NNI The SSCF at the NNI is the uppermost sub-layer in the protocol stack for the SAAL at the NNI. By construction, it utilizes the services of the underlying SAAL sub-layers, in combination with its own functions, to provide an overall SAAL service to
39、the SAAL user, as described below. The SAAL at the NNI provides signalling link functions for the transfer of signalling messages over one individual signalling data link. The SAAL, functions provide a signalling link for reliable transfer of signalling messages between two signalling points. A sign
40、alling message delivered by the higher levels is transferred over the signalling link in variable length Protocol Data Units (PDUs). For proper operation of the signalling link, the PDU comprises transfer control information in addition to the information content of the signalling message. The servi
41、ces provided by the SAAL at the NNI include: a) Assured transfer of data The SAAL service provides for the transfer of SAAL service user-data on point-to-point ATM connections. Message delimitation and alignment, error detection, and error correction are part of the assured data transfer service of
42、this SAAL. The SAAL supports the transfer of octet aligned SDUs from a minimum of 5 octets up to a maximum of 4096 octets (i.e. maximum information size k in SD PDU). The Recommendation Q.2140 (OY95) 3 - ITU-T RECMN*Q.2140 75 4862571 Ob03435 173 m SAAL service generally relieves the user from dealin
43、g with loss, insertion, corruption, and misordering of data that may occur, however, in some cases where errors are not recovered in the ATM adaptation layer, SDUs may be duplicated or lost, b) Transparency of transferred information The SAAL service provides for the transparent transfer of SAAL ser
44、vice user-data. It does not restrict the content, format or coding of the information, nor interpret the structure or meaning of the information. c) Establishment and release of SAAL connections for assured transfer of data The SAAL service provides for a means to establish and release SAAL connecti
45、ons that operate in the assured mode. An initial alignment procedure may be applied during connection establishment to verify the signalling connection. Depending on the conditions, release of an SAAL connection may result in loss of SAAL user-data. d) SDU retrieval The SAAL service makes available
46、to the SAAL service user the means by which the sending SAAL service user may retrieve SDUs already delivered to the SAAL. e) Signalling link error monitoring Two signalling link error monitoring functions are provided: one that is employed while a signalling link is in service and which provides on
47、e of the criteria for taking the link out of service, and one that is employed when a link is in the proving state of the initial alignment procedure. fl Flow control The SAAL service provides, on an implementation dependent basis, indication of local congestion of the signalling link. 6 Functions o
48、f the SSCF at the NNI This clause is provided as an aid to understanding the functions of the SSCF at the NM. The state transition table (clause 12) is the definitive specification of this SSCF. If the following text is found to conflict with clause 12, clause 12 is to be followed. The definitions o
49、f the primitives and signals used in the following descriptions of the functions are described in clauses 7, 8, and 9. 6.1 Functions with no peer-to-peer messages 6.1.1 Mapping This SSCF maps primitives received from SAAL user to signals defined at the SSCOP upper layer boundary and maps signals received from the SSCOP to primitives implicitly defined at the MTP-3 lower layer boundary. AAL-MESSAGE-FOR-TRANSMISSION-request maps to AA-DATA-request. AA-DATA-indication maps to AAL-RECEIVED-MESSAGE-indication. 6.1.2 Local retrieve The local retrieve functi
