1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T I.381 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2001) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions General network requirements and functions ATM Adaptation Layer (ALL) performance ITU-T Recommendation I.38
2、1 (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 asynch
3、ronous 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.250I.29
4、9 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 functions I.
5、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.469
6、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 details,
7、 please refer to the list of ITU-T Recommendations. ITU-T I.381 (03/2001) i ITU-T Recommendation I.381 ATM Adaptation Layer (AAL) performance Summary This Recommendation describes an approach for the performance description of AAL processes. It is motivated by the need, based on field experiences, t
8、o examine more carefully the performance aspects of some specific applications of ATM network technology. The approach presented here provides a unified framework for describing the performance of processes that depend upon AAL Type 1 (AAL-1), AAL Type 2 (AAL-2), AAL Type 3/4 (AAL-3/4), AAL Type 5 (
9、AAL-5), or potentially other types of AAL. For each AAL, parameters that describe loss and delay performance are for further study. These parameters are related to relevant ATM cell transfer performance parameters from ITU-T I.356. Source ITU-T Recommendation I.381 was prepared by ITU-T Study Group
10、13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 1 March 2001. Keywords AAL PDU transfer outcomes, ATM Adaptation Layer (AAL), circuit emulation, constant bit rate (CBR) service, internal reference event (IRE), measurement point (MP), PDU reference event (PRE), quality of service
11、 (QoS), reference event. ii ITU-T I.381 (03/2001) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for study
12、ing technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study group
13、s 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 areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS
14、O 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 ITU draws attention to the possibility that the practice or implementation of this Recom
15、mendation may involve the use of a claimed Intellectual Property Right. 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. As of the date of app
16、roval of this Recommendation, ITU had 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 strongly urged to consult the TSB
17、 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, including photocopying and microfilm, without permission in writing from ITU. ITU-T I.381 (03/2001) iii CONTENTS Page 1 Scope. 1 2 Referenc
18、es. 1 3 Abbreviations and acronyms 1 4 Introduction. 2 5 General aspects of performance description for AAL processes 3 5.1 General considerations for internal reference event definitions for all AAL types 7 5.2 Internal reference events for AAL Type 1 10 5.2.1 Unstructured circuit emulation applica
19、tions 10 5.2.2 Structured circuit emulation applications 13 5.3 Internal Reference Events for AAL Type 2 14 5.3.1 Applications where the service specific convergence sublayer is null 14 5.3.2 Applications where the service specific convergence sublayer is not null 14 5.4 Internal Reference Events fo
20、r AAL Type 3/4. 14 5.5 Internal Reference Events for AAL Type 5 14 6 AAL PDU transfer outcomes 14 6.1 PDU transfer outcomes for AAL Type 1 15 6.1.1 Unstructured circuit emulation applications 15 6.1.2 Structured circuit emulation applications 15 6.2 PDU transfer outcomes for AAL Type 2 15 6.2.1 Appl
21、ications where the service specific convergence sublayer is null 15 6.2.2 Applications where the service specific convergence sublayer is not null 15 6.3 PDU transfer outcomes for AAL Type 3/4. 15 6.4 PDU transfer outcomes for AAL Type 5 15 7 AAL performance parameters 18 7.1 Performance parameters
22、for AAL Type 1 18 7.1.1 Circuit emulation applications. 18 7.2 Performance parameters for AAL Type 2 18 7.2.1 Applications where the service specific convergence sublayer is null 18 7.2.2 Applications where the service specific convergence sublayer is not null 18 7.3 Performance parameters for AAL T
23、ype 3/4 . 18 7.4 Performance parameters for AAL Type 5 18 7.4.1 Information loss parameter for AAL Type 5. 18 7.4.2 Information delay parameter for AAL Type 5 21 8 AAL performance objectives 21 9 Allocation of the performance objectives. 21 ITU-T I.381 (03/2001) 1 ITU-T Recommendation I.381 ATM Adap
24、tation Layer (AAL) performance 1 Scope This Recommendation specifies an approach for the performance description of AAL processes 1. It is motivated by the need, based on field experiences, to examine more carefully the performance aspects of some specific applications of ATM network technology. The
25、 approach provides a unified framework for describing the performance of a process that depends upon AAL Type 1 (AAL-1) 2, AAL Type 2 (AAL-2) 3, AAL Type 3/4 (AAL-3/4) 4, AAL Type 5 (AAL-5) 5, or potentially other types of AAL. The Recommendation defines measurement points and reference events for a
26、ll AAL types, and uses these to define PDU transfer outcomes and AAL performance parameters for AAL Type 5 (PDU transfer outcomes and AAL performance parameters for other AAL Types are FFS). 2 References The following ITU-T Recommendations and other references contain provisions which, through refer
27、ence 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; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most
28、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.363 (1993), B-ISDN ATM Adaptation Layer specification. 2 ITU-T I.363.1 (1996), B-ISDN ATM Adaptation Layer specification: Type 1 AAL. 3 ITU-T
29、 I.363.2 (2000), B-ISDN ATM Adaptation Layer specification: Type 2 AAL. 4 ITU-T I.363.3 (1996), B-ISDN ATM Adaptation Layer specification: Type 3/4 AAL. 5 ITU-T I.363.5 (1996), B-ISDN ATM Adaptation Layer specification: Type 5 AAL. 6 ITU-T I.356 (2000), B-ISDN ATM layer cell transfer performance. 7
30、ITU-T I.371 (2000), Traffic control and congestion control in B-ISDN. 8 ITU-T I.350 (1993), General aspects of quality of service and network performance in digital networks, including ISDNs. 9 ITU-T I.353 (1996), Reference events for defining ISDN and B-ISDN performance parameters. 10 ITU-T G.823 (
31、2000), The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy. 11 ITU-T G.824 (2000), The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy. 3 Abbreviations and acronyms This Recommendation uses the follow
32、ing abbreviations: AAL ATM Adaptation Layer ATM Asynchronous Transfer Mode 2 ITU-T I.381 (03/2001) CBR Constant Bit Rate CDV Cell Delay Variation CER Cell Error Ratio CLR Cell Loss Ratio CMR Cell Misinsertion Rate CPCS Common Part Convergence Sublayer CPS Common Part Sublayer CS Convergence Sublayer
33、 MP Measurement Point PCI Protocol Control Information PDU Protocol Data Unit PRE PDU Reference Event SAP Service Access Point SAR Segmentation and Reassembly Sublayer SDU Service Data Unit SECBR Severely Errored Cell Block Ratio SRE SDU Reference Event SSCS Service Specific Convergence Sublayer VBR
34、 Variable Bit Rate VC Virtual Channel VP Virtual Path 4 Introduction This Recommendation specifies an approach for the performance description of AAL processes 1. It is motivated by the need, based on field experiences, to examine more carefully the performance aspects of some specific applications
35、of ATM network technology. A means for describing, in a standardized manner, the performance aspects of particular ATM Adaptation Layer (AAL) processes is needed. The approach provides a unified framework for describing the performance of a process that depends upon AAL Type 1 (AAL-1) 2, AAL Type 2
36、(AAL-2) 3, AAL Type 3/4 (AAL-3/4) 4, AAL Type 5 (AAL-5) 5, or potentially other types of AAL. The description of performance provided by specific AAL types is important for characterizing and measuring the performance of specific telecommunications applications or services that are supported in whol
37、e or in part by ATM-based telecommunications technology. As such applications can be quite diverse in nature, specific performance analysis for each such application is generally needed. While a standardized means for performance description at the ATM layer is available 6, performance analysis for
38、a specific ATM-based application must currently invoke specialized methods to account for relevant aspects of the particular AAL used by that application. This Recommendation provides a unified framework for the performance description of any ATM-based application in terms of an approach that uses s
39、tandardized methods up to the point at which AAL layer actions have been completed. Examples of the diverse nature of applications supported by specific AAL types are as follows. AAL-1 supports Deterministic Bit Rate applications that generally have sensitivity to Cell Delay ITU-T I.381 (03/2001) 3
40、Variation, AAL-2 is intended to support bandwidth-efficient transmission for low-rate, short length packet applications that are delay sensitive 3, and has the potential for supporting significant emerging uses such as wireless in combination with ATM. AAL-5 processes are significant for popular and
41、 emerging ATM applications, which include Transmission Control Protocol/Internet Protocol (TCP/IP) services supported over ATM-based network equipment and the ATM-based Available Bit Rate (ABR) transfer capability 7. This Recommendation first reviews some general aspects of performance description a
42、s they apply to AAL processes. The establishment of reference events that are suitable for measuring the performance of an AAL process is addressed from the viewpoints of both the AAL Service Access Point (SAP) and currently established Measurement Points within telecommunications networks. The Reco
43、mmendation then proposes an approach for the performance description of AAL processes that is consistent with the general structure provided in ITU-T I.350 8 and with the use of the reference events specified in ITU-T I.353 9. The remainder of this Recommendation is organized as follows. Clause 5 gi
44、ves a general discussion of performance description for the AAL. This section includes definitions of appropriate Measurement Points, PDU Reference Events, and Internal Reference Events for each AAL type. This is followed by a discussion of the various AAL PDU transfer outcomes in clause 6. Clause 7
45、 describes the performance parameters for each AAL type. 5 General aspects of performance description for AAL processes This clause gives a general description of Measurement Points (MPs), Internal Reference Events (IREs), and PDU Reference Events (PREs) for all AAL types. Then, specific definitions
46、 of IREs are given for each AAL type. An AAL provides functionality to facilitate the use of ATM layer cell transfer capabilities by higher layer processes, and a specific AAL type is selected to meet the needs of the particular higher layer process associated with a given application. Figure 1 show
47、s the relations between relevant protocol layers and their associated Service Access Points (SAPs). Figure 1 is consistent with ITU-T I.363 1 and is applicable to all of the currently defined AAL types. To describe the performance of an AAL process consistent with the general structure provided in I
48、TU-T I.350, it is necessary to define appropriate AAL Protocol Data Unit (PDU) Reference Events, and to then define relevant performance parameters based on these Reference Events. Consistent with ITU-T I.353, the PDU Reference Events are defined at observable MPs, i.e. at physical locations. Each P
49、RE approximates an Internal Reference Event defined within the protocol stack. The IREs are ideally the reference events one would like to measure to determine the AAL performance. However, since the IREs are referred to interfaces within the protocol stack, they are generally not physically accessible with test sets. Each PRE is defined to approximate a respective IRE, and is observable at an MP with a suitable test set, i.e. the PRE is defined based on physical layer test access. The IRE for each AAL is
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