1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T I.363.2 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2000) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions Protocol layer requirements B-ISDN ATM Adaptation Layer specification: Type 2 AAL ITU-T Recommendation I.
2、363.2 (Formerly CCITT Recommendation) ITU-T I-SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE Terminology I.110I.119 Description of ISDNs I.120I.129 General modelling methods I.130I.139 Telecommunication network and service attributes I.140I.149 General description of as
3、ynchronous transfer mode I.150I.199 SERVICE CAPABILITIES Scope I.200I.209 General aspects of services in ISDN I.210I.219 Common aspects of services in the ISDN I.220I.229 Bearer services supported by an ISDN I.230I.239 Teleservices supported by an ISDN I.240I.249 Supplementary services in ISDN I.250
4、I.299 OVERALL NETWORK ASPECTS AND FUNCTIONS Network functional principles I.310I.319 Reference models I.320I.329 Numbering, addressing and routing I.330I.339 Connection types I.340I.349 Performance objectives I.350I.359 Protocol layer requirements I.360I.369 General network requirements and function
5、s I.370I.399 ISDN USER-NETWORK INTERFACES Application of I-series Recommendations to ISDN user-network interfaces I.420I.429 Layer 1 Recommendations I.430I.439 Layer 2 Recommendations I.440I.449 Layer 3 Recommendations I.450I.459 Multiplexing, rate adaption and support of existing interfaces I.460I.
6、469 Aspects of ISDN affecting terminal requirements I.470I.499 INTERNETWORK INTERFACES I.500I.599 MAINTENANCE PRINCIPLES I.600I.699 B-ISDN EQUIPMENT ASPECTS ATM equipment I.730I.739 Transport functions I.740I.749 Management of ATM equipment I.750I.759 Multiplexing aspects I.760I.769 For further deta
7、ils, please refer to the list of ITU-T Recommendations. ITU-T I.363.2 (11/2000) i ITU-T Recommendation I.363.2 B-ISDN ATM Adaptation Layer specification: Type 2 AAL Summary This Recommendation specifies the AAL type 2 that provides for the bandwidth-efficient transmission of low-rate, short, and var
8、iable length packets in delay sensitive applications. More than one AAL type 2 user information stream can be supported on a single ATM connection. This Recommendation covers the specification of the frame structure of the short and variable length packets, the packing of short length packets into o
9、ne (or more) ATM cells, and the mechanisms to recover from transmission errors. This Recommendation describes the interactions between AAL type 2 and the next higher layer, between AAL type 2 and the ATM layer, and between AAL type 2 and Layer Management, as well as AAL type 2 peer-to-peer operation
10、s. Source ITU-T Recommendation I.363.2 was revised by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 24 November 2000. ii ITU-T I.363.2 (11/2000) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
11、telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Te
12、lecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some
13、 areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized
14、 operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellec
15、tual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. Howeve
16、r, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, includi
17、ng photocopying and microfilm, without permission in writing from ITU. ITU-T I.363.2 (11/2000) iii CONTENTS Page 1 Scope. 1 2 Normative References. 1 3 Definitions 1 4 Abbreviations 1 5 Conventions 3 6 General framework of AAL type 2. 3 6.1 Structure of AAL type 2 . 3 6.2 Primitives provided by AAL
18、type 2 for higher layer 5 6.3 Information flow across the AAL-ATM boundary. 5 7 General framework of AAL type 2 Common Part Sublayer (CPS) . 6 7.1 Service provided by AAL type 2 CPS 6 7.2 Primitives between AAL type 2 CPS and SSCS entities 7 8 Interaction with Management and Control Plane . 7 8.1 Ma
19、nagement Plane 7 8.1.1 Management Plane interaction with AAL type 2 CPS User Plane 7 8.2 Control Plane 8 9 Format and coding of AAL type 2 Common Part Sublayer (CPS) 8 9.1 Format and coding of the CPS-Packet 9 9.2 Format and coding of the CPS-PDU. 10 9.2.1 CPS-PDU start field (STF) 10 9.2.2 CPS-PDU
20、payload . 11 10 Procedure of AAL type 2 Common Part Sublayer (CPS) 11 10.1 CPS transmitter. 15 10.2 CPS receiver . 22 10.3 Summary of error indications to Layer Management. 27 11 Summary of parameters and values for the AAL type 2 27 Annex A Data unit naming convention. 29 Annex B Functional model f
21、or the AAL type 2 30 Annex C Switching Aspects of AAL type 2 Connections 31 C.1 Introduction. 31 C.2 Definitions 31 C.3 Basic principles of switched AAL type 2 connections. 32 iv ITU-T I.363.2 (11/2000) Page C.4 AAL type 2 connections . 33 C.4.1 Connection-definition 33 C.4.2 Connection identifiers
22、33 C.4.3 AAL type 2 connection/AAL type 2 path relation 33 C.5 Aspects of AAL type 2 connections . 33 C.5.1 General characteristics of AAL type 2 connections 33 C.5.2 Establishment and release of an AAL type 2 connection 34 C.6 Bibliography . 34 Appendix I Example of packing CPS-Packets into ATM cel
23、ls 34 I.1 Multiplexing and packing of equal length CPS-Packets 34 I.2 Multiplexing and packing of different length CPS-Packets . 37 I.3 Multiplexing and packing of maximum length CPS-Packets. 39 Appendix II Protocol Implementation Conformance Statement (PICS) Proforma 41 II.1 Introduction. 41 II.1.1
24、 Scope . 41 II.1.2 Normative references. 41 II.1.3 Abbreviations. 41 II.1.4 Conformance statement . 42 II.2 PICS Proforma 42 II.2.1 Identification of the PICS Proforma Corrigenda. 42 II.2.2 Instructions for completing the PICS Proforma 42 II.2.3 Identification of the implementation . 43 II.2.4 Globa
25、l Statement of Conformance 44 II.2.5 Timers 52 ITU-T I.363.2 (11/2000) 1 ITU-T Recommendation I.363.2 B-ISDN ATM Adaptation Layer specification: Type 2 AAL 1 Scope This Recommendation specifies the AAL type 2 that provides for the bandwidth-efficient transmission of low-rate, short, and variable len
26、gth packets in delay sensitive applications. More than one AAL type 2 user information stream can be supported on a single ATM connection. This Recommendation covers the specification of the frame structure of the short and variable length packets, the packing of short length packets into one (or mo
27、re) ATM cells, and the mechanisms to recover from transmission errors. This Recommendation describes the interactions between AAL type 2 and the next higher layer, between AAL type 2 and the ATM layer, and between AAL type 2 and Layer Management, as well as AAL type 2 peer-to-peer operations. 2 Norm
28、ative References The following ITU-T 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 rev
29、ision; all users of 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 published. 1 ITU-T I.361 (1999), B-ISDN ATM l
30、ayer specification. 2 ITU-T X.200 (1994), Information technology Open Systems Interconnection Basic Reference Model: The basic model. 3 ITU-T X.210 (1993), Information technology Open Systems Interconnection Basic Reference Model: Conventions for the definition of OSI services. 4 ITU-T I.371 (2000),
31、 Traffic control and congestion control in B-ISDN. 3 Definitions This Recommendation is based upon the concepts developed in ITU-T X.200 2 and X.210 3. Details of the data unit naming convention used in this Recommendation can be found in Annex A. 4 Abbreviations This Recommendation uses the followi
32、ng abbreviations. AAL ATM Adaptation Layer AAL-CEP AAL Connection End Point AAL-SDU AAL Service Data Unit ANP AAL type 2 Negotiation Procedures ATC ATM Transfer Capability ATM Asynchronous Transfer Mode 2 ITU-T I.363.2 (11/2000) ATM-CEP ATM Connection End Point ATM-SDU ATM Service Data Unit AUU ATM-
33、User-to-ATM-User Indication CEP Connection End Point CI Congestion Indication CID Channel Identifier CLP Cell Loss Priority CPS Common Part Sublayer CPS-INFO CPS Interface Data CPS-PDU CPS Protocol Data Unit CPS-PH CPS Packet Header CPS-PP CPS Packet Payload CPS-SDU CPS Service Data Unit CPS-UUI CPS
34、 User-to-User Indication HEC Header Error Control LI Length Indication LM Layer Management LSB Least Significant Bit MSB Most Significant Bit OAM Operation and Maintenance OSF Offset Field PAD Padding PCI Protocol Control Information PDU Protocol Data Unit QoS Quality of Service RLP Received (Cell)
35、Loss Priority SAP Service Access Point SDL Specification and Description Language SDU Service Data Unit SLP Submitted (Cell) Loss Priority SN Sequence Number SSCS Service Specific Convergence Sublayer SSCS-PDU SSCS Protocol Data Unit STF Start Field UUI User-to-User Indication VCC Virtual Channel Co
36、nnection ITU-T I.363.2 (11/2000) 3 5 Conventions The AAL type 2 receives from the ATM layer the information in the form of a 48-octet ATM Service Data Unit (ATM-SDU). The AAL type 2 passes to the ATM layer information in the form of a 48-octet ATM-SDU. 6 General framework of AAL type 2 6.1 Structure
37、 of AAL type 2 The AAL type 2 is subdivided into the Common Part Sublayer (CPS) and the Service Specific Convergence Sublayer (SSCS) as shown in Figure 1. For more detail, see Annex B. T1310250-97SAPService Specific Convergence Sublayer(may be null)PrimitivesCommon Part SublayerSAPAALCPSSSCSCommonPa
38、rtCPS Common Part SublayerSAP Service Access PointSSCS Service Specific Convergence SublayerFigure 1/I.363.2 Structure of the AAL type 2 Different SSCS protocols may be defined to support specific AAL type 2 user services, or groups of services. The SSCS may also be null, merely providing for the ma
39、pping of the equivalent AAL primitives to the AAL type 2 CPS primitives and vice versa. SSCS protocols are defined in separate Recommendations. The AAL type 2 provides the capabilities to transfer AAL-SDUs from one AAL-SAP to one other AAL-SAP through the ATM network (see Figure 2 a). The AAL type 2
40、 in non-assured operation provides the capability to transfer the AAL-SDUs from one AAL-SAP to more than one AAL-SAP through the point-to-multipoint ATM layer capability (see Figure 2 b). 4 ITU-T I.363.2 (11/2000) T1311200-97AAL connectionAAL-entity(Source)Point-to-multipointATM layer connectionAALA
41、TMAAL-SAP AAL-SAP AAL-SAPAAL-entity(Destination)AAL-entity(Destination)AAL-SAPAAL-SAPAALAAL connectionAAL-entityAAL-entityPoint-to-pointATM layer connectionATMa) Point-to-point AAL connection b) Point-to-multipoint AAL connection provided bypoint-to-multipoint ATM layer capabilityFigure 2/I.363.2 Th
42、e AAL type 2 users have the capability to select a given AAL-SAP associated with the QoS (for example, delay and loss sensitivity) required to transport that AAL-SDU (see Figure 3). The AAL type 2 makes use of the service provided by the underlying ATM layer. Multiple AAL connections may be associat
43、ed with a single ATM layer connection, allowing multiplexing at the AAL; multiplexing in the AAL type 2 occurs in the Common Part Sublayer (CPS). The AAL user selects the QoS provided by the AAL through the choice of the AAL-SAP used for data transfer. In this version of the Recommendation, Quality
44、of Service (QoSxin Figure 3) is provided by the ATM layer and there exists no standardized means to provide QoS at the AAL type 2 layer. ITU-T I.363.2 (11/2000) 5 T1310270-97AAL-SAP1AAL-SAP2AAL-SAP3(QoS1)(Qo3)(QoS2)ATM-SAPmATM-SAPnAAL LayerATM LayerService providedto the AAL-usersMakes use of theund
45、erlying ATMLayer serviceNOTE How QoS at the AAL-SAP is mapped into the ATM-SAP QoS in the event of multiplexing in the AAL is for further study.Figure 3/I.363-2 Relation between AAL-SAP and ATM-SAP The switching aspects of AAL type 2 connections are specified in Annex C. 6.2 Primitives provided by A
46、AL type 2 for higher layer The primitives that cross the AAL type 2 SAP are service-specific and contained in Recommendations that specify SSCS protocols. The SSCS may be null, merely providing for the mapping of the equivalent AAL primitives to CPS and vice versa. In this case, the primitives for t
47、he AAL are equivalent to the AAL type 2 CPS primitives (see 7.2) but identified as AAL-UNITDATA.request and AAL-UNITDATA.indication consistent with the primitive naming convention at a SAP. 6.3 Information flow across the AAL-ATM boundary The AAL type 2 makes use of the ATM layer services as defined
48、 in ITU-T I.361 1. The primitives that cross the ATM-SAP are defined in ITU-T I.361 1. They are summarized in Table 1. In the event of any difference between the following summary and the definitions in ITU-T I.361, the definitions in ITU-T I.361 take precedence. 6 ITU-T I.363.2 (11/2000) Table 1/I.
49、363.2 Primitives and parameters of the ATM layer Parameter ATM-DATA request ATM-DATA indication Comments ATM-SDU (INFO) m m 48 octets of ATM user data ATM-User-to-ATM-User Indication (AUU) (Note) m m 1 bit of ATM user information Submitted Loss Priority (SLP) (Note) m CLP = 1 increases the probability that the ATM network may discard the cell Received Loss Priority (RLP) m The CLP may have been modified by ATM network from “0“ to “1“ Congestion Indication (CI) (Note) o m CI = “1“ indicates that congestion has be
