1、STD-ITU-T RECMN 1.3b3-S-ENGL 177b m 48b257L Ob350bl T117 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.363.5 (08196) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions - Protocol layer requirements B-ISDN ATM Adaptati
2、on Layer specification: Type 5 AAL ITU-T Recommendation 1.363.5 (Previously CClTT Recommendation) For further details, please refer to ITU-T List of Recommendations. - STD.ITU-T RECHN 1.3b3.5-ENGL L99b D L18b2591 Ob350b3 881 m ITU-T RECOMMENDATION 1.363.5 B-ISDN ATM ADAPTATION LAYER SPECIFICATION: T
3、YPE 5 AAL Summary The ATM Adaptation Layer (AAL) type 5 enhances the service provided by the ATM layer to support functions required by the next higher layer. This AAL performs functions required by the user, control and management planes and supports the mapping between the ATM layer and the next h
4、igher layer. The AAL type 5 supports the non-assured transfer of user data frames. The data sequence integrity is maintained and transmission errors are detected. The AAL type 5 is characterized by transmitting in every ATM cell (but the last) of a PDU 48 octets of user data, i.e., in most of the ce
5、lls there is no overhead encountered. In a new Annex E, the corrupted data delivery option is specified. Source ITU-T Recommendation 1.363 was prepared by the ITU-T Study Group XVIII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). The current revision which lead to different I
6、TU-T Recommendations (e.g., ITU-T Recommendation 1.363.5 for the AAL type 5) for the different AAL types was prepared and approved by the ITU-T Study Group 13 (1993-1996) on the 27th of August 1996. Keywords ATM Adaptation Layer (AAL), Asynchronous Transfer Mode (ATM), Broadband Integrated Services
7、Digital Network (B-ISDN) 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 technical, operat
8、ing 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, in their t
9、urn, 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 collaborative
10、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 or implementat
11、ion 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 development process.
12、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 therefore stron
13、gly 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 Recommendation 1.363.5 (
14、08/96) CONTENTS Page 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Abbreviations . 1 5 Conventions 2 6 Framework of AAL type 5 . 3 7 Service provided by the Common Part ofthe AAL type 5 5 7.1 Primitives for the AAL type 5 6 7.2 Primitives for the CPCS of the AAL type 5 . 6 7.2.1 Primitives fo
15、r the data transfer service 6 7.2.2 Primitives for the abort service . 7 7.3 Primitives for the SAR sublayer of the AAL type 5 . 8 7.3.1 Primitives for the data transfer service 8 8 Interaction with the management and control plane . 8 8.1 Management plane 8 8.2 Control plane 8 9 Functions. structur
16、e and coding of the AAL type 5 . 9 9.1 Segmentation and Reassembly (SAR) sublayer . 9 9.1.1 Functions of the SAR sublayer 9 9.1.2 SAR-PDU structure and coding 9 9.2 Convergence Sublayer (CS) . 9 9.2.1 Functions, structure and coding for the CPCS 9 10 Procedures 10.1 Procedures for the SAR sublayer 1
17、 O . 1.1 State variables of the SAR sublayer at the sender side . 10.1.2 Procedures of the SAR sublayer at the sender side . 1 O . 1.3 State variables for the SAR sublayer at the receiver side 10.1.4 Procedures of the SAR sublayer at the receiver side . 10.2 Procedures of the CPCS for the Message Mo
18、de service 10.2.1 State variables of the CPCS at the sender side 10.2.2 Procedures ofthe CPCS at the sender side 10.2.3 State variables of the CPCS at the receiver side . 10.2.4 Procedures ofthe CPCS at the receiver side . 13 13 13 13 13 13 13 13 14 14 14 . Recommendation 1.363.5 (08196) 111 10.3 Pr
19、ocedures for the CPCS for the Streaming Mode service 10.4 Summary of parameters and values for an AAL type 5 connection . Annex A - Details of the data unit naming convention . Annex B - General framework ofthe AAL type 5 B . 1 Message segmentation and reassembly B.2 PDU headers, trailers and termin
20、ology . B.3 Examples of the segmentation and reassembly process . Annex C - Functional model for the AAL type 5 . Annex D - SDL diagram for the SAR and the CPCS of the AAL type 5 . D . 1 SDL for the SAR sublayer D . 1.1 The SAR sender D . 1.2 The SAR receiver D.2 SDL for the Common Part CS (CPCS) pr
21、ocedures D.2.1 The CPCS sender D.2.2 The CPCS receiver Annex E - Corrupted data delivery option E . 1 Service provided by corrupted data delivery option . E.2 Parameter definitions E.3 Procedures to provide corrupted data delivery for the message mode service . E.4 Procedures to provide corrupted da
22、ta delivery for the streaming mode service . ES SDL representation of procedures to provide corrupted data delivery . Appendix I - Example CPCS-PDUs for the AAL type 5 Appendix II - Insight into service provided by the procedures of Annex E . Page 15 15 16 18 18 18 18 21 22 22 22 23 23 23 23 29 29 2
23、9 30 32 32 39 40 iv Recommendation 1.363.5 (08/96) . Recommendation 1.363.5 B-ISDN ATM ADAPTATION LAYER SPECIFICATION: TYPE 5 AAL (Geneva, 1996) 1 Scope This Recommendation describes the AAL type 5, the interactions between the AAL type 5 Common Part and the next higher layer, the AAL type 5 Common
24、Part and the ATM layer, as well as the AAL type 5 Common Part peer-to-peer operations. This Recommendation is applicable to equipment to be attached to a B-ISDN User Network Interface (UNI) or B-ISDN Network Node Interface (NNI) when the services of the AAL type 5 are to be supported. 2 Normative re
25、ferences The following ITU-T Recommendations and other references contain provision 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; al
26、l 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. 11 ITU-T Recommendation 1.361 (1 999, B-ISD
27、NATM layer speciJication. 2 ITU-T Recommendation X.200 (1994), Information technology - Open Systems , Interconnection - Basic reference model: The Basic Model. 3 ITU-T Recommendation X.210 (1 993), Information technology - Open Systems Interconnection - Basic reference model: Conventions for the de
28、finition of OSI services. 3 Definitions This Recommendation is based upon the concepts developed in Recommendations 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 following abbreviation
29、s: AAL ATM Adaptation Layer AAL-SAP AAL Service Access Point AAL-SDU AAL Service Data Unit ATM Asynchronous Transfer Mode ATM-SDU ATM Service Data Unit AUU ATM User-to-ATM-User Indication CPCS Common Part Convergence Sublayer Recommendation 1.363.5 (08196) 1 CPCS-CI CPCS-IDU CPCS-LP CPCS-PDU CPCS-SD
30、U CPCS-uu CPI CRC CS ID Length LSB M MM MSB NNI i PAD QOS RS SAR SAR-CI SAR-LP SAR-PDU SAR-SDU SM sscs SSCS-PDU UNI CPCS Congestion Indication CPCS Interface Data Unit CPCS Loss Priority CPCS Protocol Data Unit CPCS Service Data Unit CPCS User-to-User Indication Common Part Indicator Cyclic Redundan
31、cy Check Convergence Sublayer Interface Data Length of CPCS-PDU Payload Least Significant Bit More Message Mode Most Significant Bit Network Node Interface Padding Quality of Service Reception Status Segmentation and Reassembly (Sublayer) SAR Congestion Indication SAR Loss Priority SAR Protocol Data
32、 Unit SAR Service Data Unit Streaming Mode Service Specific Convergence Sublayer SSCS Protocol Data Unit User Network Interface 5 Conventions The AAL type 5 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 layer informat
33、ion in the form of a 48-octet ATM-SDU. The primitives between the ATM layer and the ML type 5 are defined in Recommendation 1.361 l. 2 Recommendation 1.363.5 (08/96) 6 Framework of AAL type 5 The Convergence Sublayer (CS) has been subdivided into the Common Part CS (CPCS) and the Service Specific CS
34、 (SSCS) as shown in Figure 1. The CPCS and the SAR sublayer are called the “Common Part of the AAL type 5“. Further clarification can be found in Annex B. SAP CS I I “P Common Part CS SAR (common) a) Message Mode service CP,SL- - I “_ J Interface to the Common Part of _“ CPCS-IDU CPCS-IDU CPCS-IDU I
35、 the-type5 CPCS-IDU CPCS-IDU *,* “_ “_ CPCS-PDU trailer “_“ T1311210-97 b) Streaming Mode service Figure A.2D.363.5 - Message and Streaming modes of service at the AAL type 5 interface Recommendation 1.363.5 (08/96) 17 ANNEX B General framework of the ML type 5 This annex provides a description of t
36、he general framework of the AAL type 5 including SAR and CPCS-PDU formats. B.l . Message segmentation and reassembly Figure B.1 provides a generic interpretation of the segmenting of a SAR-SDU (message) into SAR- PDUs where the AUU bit in the header of the associated ATM-$DU is set to “O” and the la
37、st SAR- PDU where the AUU bit is set to It 1 I. n I SAR-SDU Wessage) “segment” “segment” Figure B.lfi.363.5 - Message segmentation and reassembly B.2 PDU headers, trailers and terminology Figure B.2 builds on the generic view of message segmentation of Figure A.l to incorporate the relevant PDU head
38、ers and trailers and appropriate terminology on the basis of the AUU bit being set to “O” or 1 I. B.3 Examples of the segmentation and reassembly process Figure B.3 shows schematically a successful segmentation and reassembly of a CPCS user PDU in message mode. 18 Recommendation 1.363.5 (08/96) CPCS
39、-SDU I CPCS-PDU payload 4 CPCS-PDU c Auu I SAR-PDU payload O I 1 SAR-PDU payload O LSAR-PDU-) I A SAR-PDU- I I I I I ATM-SDU I I Cell information field 1 I I I T130231W3 d-ATM-PDU = Ce1l-b Figure B.2D.363.5 - PDU headers, trailers and terminology Recommendation 1.363.5 (08/96) 19 CPCS-UNITDATA invok
40、e CPCS . Add PAD field Add CPCS trailer SAR-UNITDATA invoke SAR - Set AUU bit AUU=O - SAR-PDU AUU=O SAR-PDU + AUU=O SAR-PDU AUU=l t SAR-PDU Interpret AUU bit SAR- SAR- UNITDATA UNITDATA -,-” signal signal signal CPCS Strip PAD field Strip CPCS trailer CPCS-UNITDATA signal T13M320-93 Figure B.3A.363.
41、5 - Successful segmentation and reassembly of a CPCS user PDU 20 Recommendation 1.363.5 (08196) ANNEX C Functional model for the AAL type 5 For the AAL type 5, the functionality of the SSCS may provide only for the mapping of the equivalent primitives of the AAL to the CPCS and vice versa. On the ot
42、her hand, the SSCS may implement functions such as assured data transfer. Such functions, however, are not shown in Figures C.l and C.2. The functional model of the AAL type 5 at the sender side is shown in Figure C.l. The model consists of several blocks that cooperate to provide the AAL type 5 ser
43、vice. The SAR and CPCS blocks that are paired represent the segmentation state machine. The functional model of the AAL type 5 at the receiver side is shown in Figure C.2. The model consists of several blocks that cooperate to provide the AAL type 5 service. The SAR and CPCS blocks that are paired r
44、epresent the reassembly state machine. NOTE - Layer management interactions require further study. 71 CPCS-UNITDATA invoke 18 I I CPCS-U-ABORT invoke I I I ATM-DATA request 3 Figure C.lh.363.5 - Functional model for the AAL type 5 (sender side) Recommendation 1.363.5 (08/96) 21 t CPCS-U-ABORT signal
45、 CPCS-P-ABORT Signal f T I l L ATM-DATA indication Tl W1 70-93 NOTE -Concerning the SSCS, the functional model is an example only. Possible finctions in the SSCS (.e. multiplexing) are not shown. The SSCS is specified in other Recommendations. Figure C.2fi.363.5 - Functional model for the AAL type 5
46、 (receiver side) ANNEX D SDL diagram for the SAR and the CPCS of the AAL type 5 Procedures for delivery of corrupted data are not included in this annex; CPCS procedures for Streaming Mode are not included in this annex. SDL diagrams for the corrupted data delivery option are shown in Annex E. NOTE
47、- Implementations may or may not make the boundary between the CPCS and the SAR sublayer visible and accessible. D.l SDL for the SAR sublayer This subclause contains the SDL specifications for the SAR procedures of the AAL type 5. D.l.l The SAR sender The SAR sender makes use of two variables: a) pt
48、rPDU I This is a temporary variable that points into the (partial) CPCS-PDU received via the SAR- UNITDATA invoke primitive. AS successive parts of the CPCS-PDU are filled into SAR- PDU payloads, this pointer keeps pointing at the first octet within the CPCS-PDU that has not yet been sent within an
49、SAR-PDU. 22 Recommendation 1.363.5 (08/96) b) count This temporary variable keeps track of the number of octets still awaiting segmentation and transmission within an SAR-PDU. NOTE - No interactions with layer management are shown; these interactions require further study, D.1.2 The SAR receiver The SAR receiver maintains no variables. NOTE - No interactions with layer management are shown; these interactions require further study. D.2 SDL for the Common Part CS (CPCS) procedures This subclause contains the SD
