1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU BROADBAND ISDN (2.21 30 (07/94) B-ISDN SIGNALLING ATM ADAPTATION LAYER - SERVICE SPECIFIC COORDINATION FUNCTION FOR SUPPORT OF SIGNALLING AT THE USER NETWORK INTERFACE (SSFC AT UM) ITU-T Recommendation (2.21
2、30 (Previously CCIlT Recommendation”) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T RECMN*Q-2130 74 9 4862573 0576230 846 FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Te
3、lecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every fo
4、ur years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on 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 Recommend
5、ation 4.2130 was prepared by ITU-T Study Group 11 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 29th of July 1994. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized
6、 operating agency. O ITU 1995 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. COPYRIGHT International Telecommunications Union/ITU T
7、elecommunicationsLicensed by Information Handling ServicesCONTENTS 1 2 3 4 5 6 7 8 9 10 11 Scope Normative references . Abbreviations . General . Services of the SAAL at the UNI . Functions of the SSCF at the UNI and signalling protocol stack . Definition of the boundary of SSCF with layer 3 at the
8、UNI . 7.1 Primitives 7.2 State transition diagrams . Definition of the boundary of SSCF with SSCOP . 8.1 Signals 8.2 Puameters . 8.3 Sequences of Signals between SSCF and SSCOP State transition table of SSCF for supporting signalling at UNI Boundary to layer management : . Applicability of SSCOP par
9、ameters and timers to signalling at the UNI Annex A -Protocol Implementation Conformance (PICS) pro forma to Recommendation 4.2130 . Annex B . SSCF for Semi-permanent Connection (SPC) control signalling at the UNI Appendix I . Protocol data unit and related primitive sequences for establishment and
10、release of AAL connection at UNI Page 1 1 2 3 3 3 5 5 6 8 8 9 9 11 14 14 15 20 22 . Recommendation Q.2130 (07/94) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSUMMARY The ATM Adaptation Layer (AAL) is defined to enhance the service
11、s provided by the ATM layer to support the functions required by the next higher layer. Different AALS support various protocols to suit the different needs of a range of AAL service users. One particular type of AAL service is the signalling AAL (SAAL), which comprises AAL functions necessary to su
12、pport a signalling entity. The structure of the SAAL is defined in Recommendation Q.2100. The SAAL consists of a Segmentation and Reassembly function (SAR), and a Convergence Sublayer which is divided into two sublayers: a Common Part Convergence Sublayer (CPCS) and a Service Specific Convergence Su
13、blayer (SSCS). The common part protocol is defined in clause 6d.363 and is used as 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
14、 service, and the Service Specific Coordination Function (SSCF). The SSCOP is defined in Recommendation 4.21 10 and is equally well suited for use by various SSCFs. This Recommendation specifies the SSCF for signalling at the User-to-Network Interface (UNI). The SSCF at the UNI performs a coordinati
15、on function between the service required by the signalling layer 3 (Recommendation 4.293 1) user and the service provided by SSCOP. This Recommendation describes for SSCF at the UNI the mapping of primitives from layer 3 to signals of the SSCOP and vice versa. KEYWORDS ATM Asynchronous Transfer Mode
16、 AAL ATM Adaptation Layer B-ISDN Broadband Integrated Services Digital Network CPCS SAAL SAP SAR SSCF SSCOP sscs UNI Common Part Convergence Sublayer Signalling AAL Service Access Point Segmentation And Reassembly Service Specific Coordinatiii Function Service Specific Connection Oriented Protocol S
17、ervice Specific Convergence Sublayer UserNetwork Interface 11 Recommendation Q.2130 (07/94) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesRecommendation Q.2130 B-ISDN SIGNALLING ATM ADAPTATION LAYER - SERVICE SPECIFIC COORDINATION FUN
18、CTION FOR SUPPORT OF SIGNALLING AT THE USER-NETWORK INTERFACE (SSCF AT UNI) (Geneva, 1994) 1 Scope The intent of this Recommendation is to provide a function which is part of the ATM Adaptation Layer for the support of signalling (SAAL) at the UNI of the B-ISDN. This function is used to map the serv
19、ice of the Service Specific Connection Oriented Protocol (SSCOP) of the AAL to the needs of layer 3 protocols for access signalling across the UNI (e.g. Recommendation 4.2931). This function is called Service Specific Coordination Function (SSCF) for signalling at the UNI. This Recommendation specif
20、ies the Service Specific Coordination Function for support of signalling at the UNI (SSCF at UNI). It covers the aspects of the SSCF of the complete AAL structure for signalling applications at the UNI defined in Recommendation Q.2100 8, and describes the relationship to the protocol entity for acce
21、ss signalling defined in Recommendation 4.2931 5 and the Service Specific Connection Oriented Protocol 4.21 10 9. This Recommendation is applicable to equipment to be attached at either side of B-ISDN User-Network Interface (UNI) when B-ISDN access signalling is to be supported. 2 Normative referenc
22、es 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 Recommendations and other references are subject to revision: all users of
23、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 currently valid ITU-T Recommendations is regularly published. CCITT Recommendation X.200, Reference model of open system
24、s interconnection for CCIZT applications. CCIlT Recommendation X.210, OSI layer service conventions. ITU-T Recommendation I. 150, B-ISDN Asynchronous Transfer Mode Functional Characteristics. L ITU-T Recommendation 1.361, B-ISDN Asynchronous Transfer Mode (ATM) Layer specification. ITU-T Recommendat
25、ion 4.293 1, B-ISDN - Digital Subscriber Signalling System No. 2 (DSS2) - User network interface layer 3 specification for basic calVconnection control. ITU-T Recommendation Q.704, Signalling Network Functions and Messages. ITU-T Recommendation 1.363, B-ISDN ATM Adaptation Layer (AAL) specification.
26、 ITU-T Recommendation 4.2100 - B-ISDN signalling ATM Adaptation Layer (SAAL) overview description. ITU-T Recommendation Q.2110, B-ISDN ATM Adaptation Layer - Service Specijc Connection Oriented Protocol (SSCOP). ITU-T Recommendation X.290, OS1 conformance testing methodology and framework for protoc
27、ol Recommendations for CCIi“app1ications - General concepts. Recommendation Q.2130 (07/94) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services3 Abbreviations AA ATM Adaptation AAL ATM Adaptation Layer ATM Asynchronous Transfer Mode BGAK
28、Begin Acknowledge (PDU) BGN Begin (PDU) B-ISDN Broadband Integrated Services Digital Network BR Buffer Release BSVC Broadcast Signalling Virtual Channel CES Connection Endpoint Suffix CPCS Common Part Convergence Sublayer END End (PDU) ENDAK End Acknowledge (PDU) MAA Management ATM Adaptation MaxCC
29、Maximum Connection Control (Count) MaxPD Maximum Poll Data (Count) MSVC Meta-Signalling Virtual Channel MU Message Unit NNI Network Node Interface os1 Open Systems Interconnection PDU Protocol Data Unit PICS Protocol Implementation Conformance Statement PR Poll Request PSVC Point-to-point Signalling
30、 Virtual Channel RESYNC Resynchronization (Primitive) RS Resynchronization SAAL Signalling ATM Adaptation Layer SAR Segmentation And Reassembly SD Sequenced Data (PDV) SDU Service Data Unit SN Sequence Number- - SPC Semi Permanent Connection SSCF Service Specific Coordination Function SSCOP Service
31、Specific Connection Oriented Protocol sscs Service Specific Convergence Sublayer STAT Solicited Status (PDU) svc Switched Virtual Connection UD Unumbered Data (PDU) UNI User Network Interface UNIT DATA Unit Data (Pnmitive) USTAT Unsolicited Status (PDU) uu User-to-User VR Receiver State Variable 2 R
32、ecommendation Q.2130 (07/94) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services4 General The ATM Adaptation Layer used to support signalling (SAAL) is a combination of two sublayers: a common part and service specific part. The common par
33、t protocol is defined in clause 6fl.363 7. The service specific part is further split into two parts: the Service Specific Coordination Function (SSCF) and the Service Specific Connection Oriented Protocol (SSCOP). Recommendation Q.2100 8 provides an overview of this structure. Recommendation Q.2110
34、 9 specifies the SSCOP. This Recommendation specifies the SSCF at UNI. The purpose of the SAAL is to convey information between layer 3 entities across the UNI and NNI using Asynchronous Transfer Mode (ATM) virtual channels. The purpose of the SSCF at UNI is to map the UNI layer 3 protocol (Recommen
35、dation Q.293 1) to the service of the next lower layer. The definition of the SAAL takes into consideration the principles and terminology of Recommendations X.200 11 and X.210 2 - the reference model and layer service conventions for Open Systems Interconnection (OSI). The SAAL is a protocol which
36、operates at the data link layer of the OS1 architecture. NOTES 1 The ATM layer is currently defined in Recommendations 1.150 3 and 1.361 4. Layer 3 is defined in Recommendation 4.2931 5. 2 The term “layer 3” is used to indicate the layer above the SAAL, the user of the SAAL services. 5 Services of t
37、he SAAL at the UNI The following services are provided by the SAAL at the UNI: a) Unacknowledged Transfer of Data - The SAAL service provides for the unacknowledged transfer of SAAL service data units on point-to-point and point-to-multipoint ATM connections. The SAAL supports the transfer of octet
38、aligned SDUs up to a maximum of 4096 octets (i.e. maximum information size k in UD-PDU). The SAAL unacknowledged data transfer service does not relieve the user from loss or insertion of data which may occur. b) Assured Transfer of Data - The SAAL service provides for the assured transfer of SAAL se
39、rvice data units on point-to-point ATM connections. The SAAL supports the transfer of octet aligned SDUs up to a maximum of 4096 octets (i.e. maximum information size k in SD PDU). The SAAL service relieves the user from loss, insertion, corruption, and misordering of data which may occur. In some c
40、ases due to unrecoverable errors in the ATM adaptation layer, duplication or loss of SDUs may occur. c) Transparency of Transferred Informution - The SAAL service provides for the transparent transfer of SAAL service data units. It does Bot restrict the content, format or coding of information, nor
41、does it ever need to interpret its structure or meaning. d) Establishment and Release of SAAL Connections for Assured Trander of Data - The SAAL service provides a means to establish and release SAAL connections which operate in the assured mode. In some cases, the SAAL service provider may release
42、the SAAL connection. Depending on the conditions, release of an SAAL connection may result in loss of SAAL user-data. 6 Functions of the SSCF at the UNI and signalling protocol stack The SSCF performs a coordination function between the service required by the signalling layer 3 (Recom- mendation Q.
43、2931) user and the service provided by SSCOP. Figure 1 relates AAL information flows to different types of signalling virtual channels defined within the ATM Layer at the UNI. The figure also depicts how various functional blocks in a protocol stack are related to their “neighbours”. Recommendation
44、Q.2130 (07/94) 3 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services4 I- - Recommendation Q.2130 (07194) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesThe properties of the
45、protocol structure shown in Figure 1 are: 1) For support of signalling there is a one-to-one correspondence between a connection endpoint within the AAL-SAP and a connection endpoint within the ATM-SAP. 2) Any distribution of information associated with one AAL-connection within the AAL has to be ma
46、de based on PDU type (bottom up direction) or primitive type (top down direction). 3) Two types of connections are available to the AAL user, broadcast and point-to-point. The broadcast connection provides unacknowledged information transfer while the point-to-point connection primarily provides ass
47、ured information transfer, and may provide (no signalling application is known currently, making use of this capability) unacknowledged information transfer. In this case, the discrimination between the two information flows is done based on AAL-primitives with AAL-UNITDATA primitives for unacknowle
48、dged and AAL-ESTABLISH, -RELEASE, and -DATA primitives for assured information transfer. 7 Definition of the boundary of SSCF with layer 3 at the UNI 7.1 Primitives The primitives required to support the SAAL user at the UNI are shown in Table UQ.2130. TABLE UQ.2130 SAAL primitives used at the UNI G
49、eneric Name AAL-ESTABLISH AAL-RELEASE AAL-DATA AAL-UNITDATA Request X (Parameter Data) (Note) X (Parameter Data) (Note) X (Parameter Data) X (Parameter Data) Type Contents of Primitive Indication I Response I Confirm Parameter Data X (Parameter Data) (Note) X (Parameter L3 peer-to-peer Data) (Note) message X (Parameter L3 peer,to-peer Data) (Note) message Data) message X (Parameter Data) I l message L3 peer-to-peer NOTE -The use of Parameter Data in this primitive is not specifically required by applications identified at the time this Recommend
