1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.363.1 (08196) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions - Protocol layer requirements B-ISDN ATM Adaptation Layer specification: Type I AAL ITU-T Recommendation 1.3
2、63.1 (Previously CCllT Recommendation) ITU-T I-SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE 1.100-1.199 Terminology 1.110-1.119 Description of ISDNs 1.120-1.129 General modelling methods 1.130-1.139 Telecommunication network and service attributes 1.140-1.149 General
3、description of asynchronous transfer mode 1.150-1.199 SERVICE CAPABILITIES 1.200-1.299 Scope 1.200-1.209 General aspects of services in ISDN 1.210-1.219 Common aspects of services in the ISDN 1.220-1.229 Bearer services supported by an ISDN 1.230-1.239 Teleservices supported by an ISDN 1.240-1.249 S
4、upplementary services in ISDN 1.250-1.299 OVERALL NETWORK ASPECTS AND FUNCTIONS 1.300-1.399 Network functional principles 1.310-1.319 Reference models 1.320-1.329 Numbering, addressing and routing 1.330-1.339 Connection types I. 3404.349 Performance objectives 1.350-1.359 Protocoi layer requirements
5、 1.360-1.369 General network requirements and functions 1.370-1.399 ISDN USER-NETVVORK INTERFACES 1.400-1.499 Application of I-series Recommendations to ISDN user-network interfaces 1.420-1.429 Layer 1 Recommendations 1.430-1.439 Layer 2 Recommendations 1.440-1.449 Layer 3 Recommendations 1.450-1.45
6、9 Multiplexing, rate adaption and support of existing interfaces 1.460-1.469 Aspects of ISDN affecting terminal requirements 1.470-1.499 INTERNETWORK INTERFACES 1.500-1.599 MAINTENANCE PRINCIPLES 1.600-1.699 B-ISDN EQUIPMENT ASPECTS 1.700-1.799 ATM equipment 1.730-1.749 Management of ATM equipment 1
7、.750-1.799 For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION 1.363.1 B-ISDN ATM ADAPTATION LAYER SPECIFICATION: TYPE 1 AAL Source ITU-T Recommendation 1.363.1 was prepared by ITU-T Study Group 13 (1 993-1 996) and was approved under the WTSC Resolution No. 1 pr
8、ocedure on the 27th of August 1996. FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying techni
9、cal, operating and tariff questions and issuing Recommendations 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,
10、 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. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a col
11、laborative basis with IS0 and IEC. , NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice o
12、r implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation developm
13、ent process. As of the date of approval of this Recommendation, the ITU hadhad not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are th
14、erefore strongly urged to consult the TSB patent database. O ITU 1997 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. 11 Recommendat
15、ion 1.363.1 (08/96) CONTENTS Page 1 Introduction 1.1 Scope of the Recommendation . 2 AAL type 1 . 2.1 Services provided by AAL type 1 2.1.1 Definitions . 2.1.2 Primitives between AAL type 1 and the AAL user . 2.1.3 Information flow across the ATM-AAL boundary . 2.1.4 Primitives between the SAR subla
16、yer and the CS 2.2.1 Management plane 2.2 Interaction with the management and control planes . 2.2.2 Control plane . 2.3 Functions of AAL type 1 2.4 Segmentation and Reassembly (SAR) sublayer . 2.4.1 Functions of the SAR sublayer 2.4.2 SAR protocol . 2.5 Convergence Sublayer (CS) . 2.5.1 Functions o
17、f the CS . 2.5.2 Convergence Sublayer (CS) protocol Annex A . Alphabetical list of abbreviations Annex B . Data unit naming convention . Annex C . Encoding and information transfer principles . C . 1 Cell payload field encoding C.2 AAL user information transfer . Appendix I . Functional model and SD
18、L of AAL type 1 . I . 1 Functional model of the SAR . 1.2 SDL of the SAR Appendix II . Informative and example parameters for AAL type 1 protocol . II . 1 Circuit transport 11.1.1 Transport of digital channel supported by 64 kbit/s-based ISDN . II . 1.2 Transport of G.702 PDH circuit II . 1.3 Transp
19、ort of 6709 SDH circuit 11.2 Video signal transport . 11.3 Voiceband signal transport . 1 1 1 1 3 3 4 4 4 4 5 5 5 8 8 11 24 25 26 26 27 28 28 30 32 32 32 32 33 33 34 . Recommendation 1.363.1 (08/96) I11 Page Appendix III - Informative and example operations for handling of lostlmisinserted cells III
20、. 1 111.2 111.3 and for maintaining bit count integrity . Introduction . . . . . . . . . . Sequence number processing . . . . . . , . . . . . . . . . 111.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . .
21、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.2.2 Indications from the SAR sublayer . 111.2.3 Capabilities of the algorithm . . . . , . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . 111.2.4 The
22、algorithms . Mechanisms to maintain bit-count integrity and basic handling of lost/misinserted cells ., . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.3.1 Buffer-fill level monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23、. . . . . . . . 111.3.2 Cell Arrival Monitoring 35 35 35 35 35 36 36 39 40 40 iv Recommendation 1.363.1 (08/96) Recommendation 1.363.1 B-ISDN ATM ADAPTATION LAYER SPECIFICATION: TYPE 1 AAL (Geneva, 1996) 1 Introduction The ATM Adaptation Layer (AAL) enhances the service provided by the ATM layer to
24、support functions required by the next higher layer. The AAL performs functions required by the user, control and management planes and supports the mapping between the ATM layer and the next higher layer. The functions performed in the AAL depend upon the higher layer requirements. The AAL Supports
25、 multiple protocols to fit the needs of the different AAL service users. The service provided by the AAL type 1 to the higher layer and the fnctions performed are specified in this Recommendation. Abbreviations used in this Recommendation are listed in Annex A. Details of the data unit naming conven
26、tion used in this Recommendation can be found in Annex B. 1.1 Scope of the Recommendation This Recommendation describes the interactions between the AAL type 1 and the next higher layer, and the AAL type 1 and the ATM layer, as well as AAL type 1 peer-to-peer operations. Different combinations of SA
27、R (Segmentation and Reassembly) sublayer and CSs (Convergence Sublayers) provide different Service Access Points (SAPS) to the layer above the AAL. 2 ML type 1 2.1 Services provided by ML type 1 2.1.1 Definitions The layer services provided by AAL type 1 to the AAL user are: a transfer of service da
28、ta units with a constant source bit rate and the delivery of them with the same bit rate; a transfer of timing information between source and destination; 8 transfer of structure information between source and destination; e indication, if needed, of lost or errored information which is not recovere
29、d by AAL type 1. 2.1.2 Primitives between AAL type 1 and the AAL user 2.1.2.1 General At the AAL-SAP, the following primitives will be used between the ML type 1 and the ML user: From an AAL user to the AAL, e From the AAL to an AAL user, AAL-UNITDATA Request; AAL-UNITDATA Indication. Recommendation
30、 1.363.1 (08/96) 1 An AAL-UNITDATA request primitive at the local AAL-SAP results in an AAL-UNITDATA indication primitive at its peer AAL-SAP. 2.1.2.2 Definition of primitives 2.1.2.2.1 AAL-UNITDATA request AAL-UNITDATA request (DATA mandatory, STRUCTURE optional) The AAL-UNITDATA request primitive
31、requests the transfer of the AAL-SDU, i.e. contents of the DATA parameter, from the local AAL entity to its peer entity. The length of the AAL-SDU is constant and the time interval between two consecutive primitives is constant. These two constants are a function of the AAL service provided to the A
32、AL user. 2.1.2.2.2 AAL-UNITDATA indication AAL-UNITDATA indication (DATA mandatory, STRUCTURE optional, STATUS optional) An AAL user is notified by the AAL that the AAL-SDU, i.e. contents of the DATA parameter, from its peer are available. The length of the AAL-SDU should be constant and the time in
33、terval between two consecutive primitives should be constant. These two constants are a function of the AAL service provided to the AAL user. 2.1.2.3 Definition of parameters. 2.1.2.3.1 DATA parameter The DATA parameter carries the AAL-SDU to be sent or delivered. Its size depends on the specific AA
34、L layer service used, and is described in 2.5.1.1 a) to 2.5.1.4 a). 2.1.2.3.2 STRUCTURE parameter (optional use) The STRUCTURE parameter can be used when the user data stream to be transferred to the peer AAL entity is organized into groups of bits. The length of the structured block is fixed for ea
35、ch instance of the AAL service. The length is an integer multiple of 8 bits. An example of the use of this parameter is to support circuit mode bearer services of the 64 kbit/s-based ISDN. The two values of the STRUCTURE parameter are: START, and CONTINUATION. The value START is used when the DATA i
36、s the first part of a structured block which can be composed of consecutive DATA. In other cases, the structure parameter is set to CONTINUATION. The use of the STRUCTURE parameter depends on the type of AAL service provided. The use of this parameter is agreed prior to or at the connection establis
37、hment between the AAL user and the AAL. 2 Recommendation 1.363.1 (08196) 2.1.2.3.3 STATUS parameter (optional use) The STATUS parameter identifies that the DATA is judged to be non-errored or errored. The STATUS parameter has twd values: VALID, and INVALID. The INVALID status could also imply that t
38、he DATA is a dummy value. The use of the STATUS parameter and the choice of dummy value depend on the type of AAL service provided. The use of this parameter is agreed prior to or at the connection establishment between the AAL user and the AAL. 2.1.3 Information flow across the ATM-AAL boundary Rec
39、ommendation 1.361 describes the primitives exchanged between the ATM layer and the AAL. This subclause describes the usage of these primitives for AAL type 1. The AAL receives from the ATM layer the information in the form of a 48-octet ATM Service Data Unit (ATM-SDU). The AAL passes to the ATM laye
40、r information in the form of a 48-octet ATM-SDU. The submitted CLP (Cell Loss Priority) in the request primitive is set to the high priority by the AAL transmitter. The value of the receive loss priority in the indication primitive is ignored by the AAL receiver. The AUU (ATM-User-to-ATM-User) param
41、eter is set to “O“ in the request primitive. Future procedures may require that the AUU parameter can be set to “O“ or “1“. Such usage is reserved for future standardization. The congestion indication is ignored by the AAL receiver. The encoding principles for mapping information between the ATM lay
42、er and AAL type 1 are given in Annex C. 2.1.4 Primitives between the SAR sublayer and the CS 2.1.4.1 General These primitives model the exchange of information between the SAR sublayer and the Convergence Sublayer (CS). As there exists no Service Access Point (SAP) between the sublayers of the AAL t
43、ype 1, the primitives are called invoke and lsignal instead of the conventional request“ and “indication“ to highlight the absence of the SAP. Functional model and SDL of AAL type 1 is given in Appendix I. 2.1.4.2 SAR-UNITDATA invoke SAR-UNITDATA invoke at the AAL type 1 transmitter has the followin
44、g parameters: Interface data: This parameter specifies the interface data unit passed from the CS to the CSI: The Convergence Sublayer Indication (CSI), either “O“ or “l“, is passed from the CS to Sequence count: The sequence count value is passed from the CS to the SAR entity. The SAR entity. The i
45、nterface data is 47 octets, and represents a SAR-PDU payload. the SAR entity. value of sequence count starts with O, is incremented sequentially and is numbered modulo 8. Recommendation 1.363.1 (08196) 3 2.1.4.3 SAR-UNITDATA signal SAR-UNITDATA signal at the ML type 1 receiver has the following para
46、meters: o Interface data: This parameter specifies the interface data unit passed from the SAR to the 0 CSI: The CS1 is passed from the SAR to CS entity, regardless of the check status (valid or o Sequence count: The sequence count value is passed from the SAR to CS entity, regardless o Check status
47、: This parameter specifies the status of the sequence count and CSI, and has the CS entity. The interface data is 47 octets, and represents a SAR-PDU payload. invalid). of the check status (valid or invalid). value of either valid or invalid. 2.2 Interaction with the management and control planes 2.
48、2.1 Management plane The following indications may be passed from the user plane to the management plane: o errors in the transmission of user information; 0 lost or misinserted cells (further study is required on whether it is necessary to distinguish o cells with errored AAL Protocol Control Infor
49、mation (AAL-PCI) (fbrther study is required o loss of timing and synchronization; between lost and misinserted cells for management purposes); to determine if this indication is necessary for layer services supported by this AAL type); e buffer underflow and overflow. 2.2.2 Control plane For further study. 2.3 Functions of AAL type 1 The following functions may be performed in the AAL type 1 in order to enhance the ATM layer service: a) segmentation and reassembly of user information; b) blocking and deblocking of user inform
